Global LC-MS/MS targeted metabolomics using a combination of HILIC and RP LC separation modes on an organic monolithic column based on 1-vinyl-1,2,4-triazole

The paper presents an LC-MS/MS-based approach to targeted screening of both polar and non-polar metabolites using a synthesized monolithic column which is a copolymer of styrene, divinylbenzene, and 1-vinyl-1,2,4-triazole. It was shown that this column in combination with eluents 20 mM (NH4)2CO3 + NH3 (pH = 9.8, eluent A) and ACN (eluent B) allows for separation of metabolites of different nature in two modes, HILIC and RP LC, and these methods are mutually complementary. A combination of analyses based on these two modes was proposed, allowing detection of about 400 metabolites in a total time of less than 30 min. Comparison of the developed method with those utilizing commercially available columns with sorbents of various types showed that it could provide a broader metabolite coverage. Using the developed approach, metabolomic screening of dried blood spots samples of mice exposed with X-ray was performed, and metabolites that could be considered as possible markers of irradiation exposure and organ tissue damage were detected. Analysis of marker metabolites revealed metabolic pathways that were altered by radiation exposure. Comparison of the results with literature data showed the effectiveness of the developed metabolomic screening approach.

Enantioseparation by zeolitic imidazolate framework-8-silica hybrid monolithic column with sulfobutylether-β-cyclodextrin as a chiral additive in capillary electrochromatography

A zeolitic imidazolate framework (ZIF)-8-silica hybrid monolithic column was prepared by one-step sol-gel method. The stationary phase in the monolithic column was characterized by Fourier-transform infrared spectra, X-ray diffraction, thermogravimetric analysis, nitrogen adsorption/desorption, and zeta potential. The results showed that ZIF-8-silica hybrid monolithic materials had abundant functional groups, good crystallinity, large specific surface area, and good thermal stability. A capillary electrochromatography (CEC) chiral separation system was for the first time constructed with ZIF-8-silica hybrid monolithic column and sulfobutylether-β-cyclodextrin (SBE-β-CD) as a chiral additive and was applied to separate the selected single and mixed chiral compounds (13 natural amino acids and 5 chiral pesticides). Under the optimized CEC conditions, all the single analytes achieved baseline separation with resolution of 2.14-5.94 and selectivity factor of 1.06-1.49 in less than 6 min, and the mixed amino acids with similar properties were also simultaneously enantioseparated (Rs ≥ 1.82). Relative standard deviations (RSDs) of migration time and column efficiency were lower than 4.26% and did not change significantly after 200 runs, evidencing excellent reproducibility and stability. These results demonstrate that the application of SBE-β-CD as a chiral additive for ZIF-8-silica hybrid monolithic columns is a promising method for the separation of chiral compounds.

N, N'-methylene bisacrylamide/divinyl benzene based-highly cross-linked hybrid monolithic column: Production and its applications for powerful capture of four chlorophenols

In this paper, the role of the halogen bond in capillary monolithic column microextraction was explored for the first time. Benzene-1,3,5-tricarbohydrazide (BTH) was synthesized as a functional monomer, N, N'-methylene bisacrylamide (MBA) and divinyl benzene (DVB) were used as cross-linking agents, the hybrid monolithic column of poly (BTH-co-DVB-co-MBA) was prepared using methanol and polyethylene glycol as pore-forming agents and azodiisobutyronitrile as the initiator. Due to the existence of BTH, a large number of nitrogen atoms (Lewis base) were introduced into the monolithic column, which could form a halogen bond with chlorine-containing organic pollutants and enhance its adsorption performance. Based on the monolithic column, a sensitive and environment-friendly solid-phase microextraction technology was studied. The monolithic column was integrated with high-performance liquid chromatography (HPLC) to extract and detect four kinds of chlorophenol in real water samples. Under best conditions, the method showed excellent extraction ability and linearity, with a linear correlation coefficient of 0.9958-0.9987, a low detection limit (LOD) of 0.04-0.23 μg L^-1 (S/N = 3), and relative standard deviation (RSD) less than 3.09%. The recovery rate was kept between 87.30% and 123.00%, and the RSD was less than 3.83%, which indicated that the column had powerful capture performance, high precision, and strong anti-matrix interference ability in the real sample, and had potential application value in practical work.

Solid-phase microextraction with MIL-53(Al)-polymer monolithic column coupled to pressurized capillary electrochromatography for determination of chlorogenic acid and ferulic acid in sugarcane samples

In this paper, a polymer monolithic column based on poly (Butyl methacrylate-co-ethylene glycol dimethacrylate) (poly (BMA-co-EDGMA)) doped with MIL-53(Al) metal-organic framework (MOF) was prepared using an in situ polymerization method. The characteristics of MIL-53(Al)-polymer monolithic column were studied through scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FT-IR), energy-dispersive spectroscopy (EDS), X-ray powder diffractometry (XRD), and nitrogen adsorption experiment. Due to its large surface area, the prepared MIL-53(Al)-polymer monolithic column has good permeability and high extraction efficiency. Using MIL-53(Al)-polymer monolithic column for solid-phase microextraction (SPME), coupled to pressurized capillary electrochromatography (pCEC), a method for the determination of trace chlorogenic acid and ferulic acid in sugarcane was established. Under optimized conditions, chlorogenic acid and ferulic acid have a good linear relationship (r ≥ 0.9965) within the concentration range of 50.0-500 µg/mL, the detection limit is 0.017 µg/mL, and the relative standard deviation (RSD) is less than 3.2%. The spike recoveries of chlorogenic acid and ferulic acid were 96.5% and 96.7%, respectively. The results indicate that the method is sensitive, practical, and convenient. It has been successfully applied to the separation and detection of trace organic phenolic compounds in sugarcane samples.

A benzenesulfonic acid-modified organic polymer monolithic column with reversed-phase/hydrophilic bifunctional selectivity for capillary electrochromatography

Here, a styrene-based polymer monolithic column poly(VBS-co-TAT-co-AHM) with reversed-phase/hydrophilic interaction liquid chromatography (RPLC/HILIC) bifunctional separation mode was successfully prepared for capillary electrochromatography by the in situ polymerization of sodium p-styrene sulfonate (VBS) with cross-linkers 3-(acryloyloxy)-2-hydroxypropyl methacrylate (AHM) and 1,3,5-triacryloylhexahydro-1,3,5-triazine (TAT). The preparation conditions of the monolith were optimized. The morphology and formation of the poly(VBS-co-TAT-co-AHM) monolith were confirmed by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). The separation performances of the monolith were evaluated systematically. It should be noted that the incorporation of VBS functional monomer can provide π-π interactions, hydrophilic interactions, and ion-exchange interactions. Hence, the prepared poly(VBS-co-TAT-co-AHM) monolith can achieve efficient separation of thiourea compounds, benzene series, phenol compounds, aniline compounds and sulfonamides in RPLC or HILIC separation mode. The largest theoretical plate number for N,N'-dimethylthiourea reached 1.7 × 10⁵ plates/m. In addition, the poly(VBS-co-TAT-co-AHM) monolithic column showed excellent reproducibility and stability. This novel monolithic column has great application value and potential in capillary electrochromatography (CEC).

Comparative Evaluation of Reversed Stationary Phase Geometries and Greener Systems on HPLC and UHPLC Using Five Recent Hepatitis-C Antivirals

BACKGROUND

Being the most widely used LC mode, reversed phase RP-HPLC accounts for the highest percentage of HPLC separations. The main aim of the green analytical chromatographers is to enhance efficiency of separations done in short analysis time, using the ecologically safest materials and lowest energy consumption.

OBJECTIVE

Being the heart of any chromatography where the actual separations take place, LC columns had diverse varieties in their developments which involve the change in stationary phase geometries as well as particles size. The rational about column's choice is quite complicated. Totally porous, core-shell particles, and monolithic rods are stationary phase types manufactured in RP-mode. The selection of HPLC or UHPLC instrumentation is another crucial choice.

METHODS

In this research article, three different column packing phases were evaluated and compared on both HPLC and UHPLC techniques. The purpose was to explore the best rational choice of column packing as well as LC instrumentation, when using greener chromatographic conditions.

RESULTS AND CONCLUSION

The study showed a superiority of core-shell particles in both HPLC and UHPLC techniques. Moreover, this RP-morphology enabled the utilization of greener mobile phase compositions. Monolithic columns showed better accommodation of greener mobile phases' flow rates, without considerable loss of performance.

HIGHLIGHTS

The use of greener organic solvents was assessed on different stationary phase geometries. The separation efficiency for five recent antiviral drugs was evaluated for better understanding of column choice versus experimental conditions. UHPLC and HPLC were compared comprehensively at the level of applicability and cost-effectiveness.

Removal of amoxicillin via chromatographic monolithic columns: comparison between batch and continuous fixed bed

This study presented a hydrophobic interaction-based poly(HEMA-MATrp) monolithic chromatographic column (MCC) to remove amoxicillin from aqueous solutions. In addition to their porous structure, monolithic-filled columns offer superior properties without loss of performance, which is one of the points that make them unique. The specific surface area of the monolithic column synthesized by the bulk polymerization of 2-hydroxyethyl methacrylate and N-Methacryloyl-L-tryptophan. Also, poly(HEMA-MATrp) MCC has been characterized via FTIR, SEM, and elemental analysis. According to BET analysis, the specific surface area of the poly(HEMA-MATrp) monolithic chromatographic column (MCC) is 14.2 mg/g. The adsorption and desorption of amoxicillin in an aqueous solution were investigated comparatively in both continuous fixed bed and batch adsorption. The highest adsorption value of amoxicillin was determined at pH 7 in the presence of PBS as 62.11 mg/g. The appropriate adsorption isotherm for the adsorption of amoxicillin was Langmuir, and the reaction kinetics was pseudo-second-order. No significant loss was observed for the adsorption capacity of poly(HEMA-MATrp) MCC after the 5 cycles of adsorption-desorption studies. Also, the loss for the adsorption capacity of the monolithic column is just %5.2 after 6-month storage, proving the reusability and storability of the monolithic column.

Evaluating micellar liquid chromatographic methods on octadecyl particle-based and monolithic columns to predict the skin permeation of drug and cosmetic molecules

A micellar liquid chromatographic method was developed to assist in the modeling of the skin permeability of pharmaceutical and cosmetic compounds. The composition of the mobile phase was determined by means of a two-factor central composite design, after which it was tested on both a particle-based and monolithic column. The latter provided the opportunity to increase the flow rate from 1 to 8 mL/min without reaching too high backpressures. The micellar conditions allowed analyzing a large test set of compounds with diverse characteristics with just one mobile-phase composition. The obtained experimental chromatographic descriptors besides two sets of theoretical molecular descriptors were used to model the skin permeability coefficient log K_p, applying multiple linear regression and partial least squares regression approaches. The micellar method on the monolithic column provided useful models with similar or even slightly better performance parameters than the method on the particle-based column. Furthermore, a much faster analysis can be achieved when applying a flow rate of 8 mL/min, making the micellar monolithic method ideal to estimate skin permeability.

Ligand fishing via a monolithic column coated with white blood cell membranes: A useful technique for screening active compounds in Astractylodes lancea

The cell membrane-coated monolithic column (CMMC) ligand fishing assay is an interesting approach set up for the study of natural products (NPs). NPs such as Atractylodes lancea contain many compounds. Traditional methods used to separate compounds and determine active compounds by pharmacological tests are time-consuming and inefficient. Therefore, an alternative method is required to determine active compounds in NPs. Here, white blood cells were broken, and the white blood cell membranes (WBCMs) were immobilized on the surface of a monolithic column to form a CMMC. The column was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and confocal laser scanning microscopy. Combined with gas chromatography/mass spectrometry (GC/MS), the CMMC was used to screen active compounds in Atractylodes lancea. Three potential active compounds including hinesol, β-eudesmol, and 4-phenylbenzaldehyde were discovered. A molecular docking assay demonstrated that these compounds could bind to MD-2 laid on WBCMs. In addition, antiinflammatory effects by the discovered compound in vitro were confirmed, and β-eudesmol showed a concentration-dependent inhibitory effect on the tumor necrosis factor (TNF)-α of a RAW264.7 cell (P < 0.05). The CMMC ligand fishing assay exhibits good selectivity, great speed effects and is a potentially reliable tool for drug discovery in NPs.

S-citalopram imprinted monolithic columns for capillary electrochromatography enantioseparations

In this study, the molecular imprinting method was used to separate enantiomeric forms of chiral antidepressant drug, R,S-citalopram (R,S-CIT) in aqueous solution by CEC system combining the advantages of capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC). For that, an amino acid-based molecularly imprinted monolithic capillary column was designed and used as a stationary phase for selective separation of S-citalopram (S-CIT) for the first time. S-CIT was selectively separated from the aqueous solution containing the other enantiomeric form of R-CIT, which is the same in size and shape as the template molecule. Morphology of the molecularly imprinted (MIP S-CIT) and non-imprinted (NIP S-CIT) monolithic capillary columns was observed by scanning electron microscopy. Imprinting efficiency of MIP S-CIT monolithic capillary column used for selective S-CIT separation was verified by comparing with NIP S-CIT and calculated imprinting factor (I.F:1.81) proved the high selectivity of the MIP S-CIT for S-CIT. Cavities formed for S-CIT form enabled selective (α = 2.08) separation of the target molecule from the other enantiomeric R-CIT form. Separation was achieved in a short period of 10 min, with the electrophoretic mobility of 7.68 × 10^-6 m² /Vs for R,S-CIT at pH 7.0 10 mM PB and 50% ACN ratio. The performance of both MIP S-CIT and NIP S-CIT columns was estimated by repeating the R,S-CIT separations with intra-batch and inter-batch studies for reproducibility of retention times of R,S-CITs. Estimated RSD values that are lower than 2% suggest that the monolithic columns separate R,S-CIT enantiomers without losing separation efficiency.

Chiral covalent organic framework-monolith as stationary phase for high-performance liquid chromatographic enantioseparation of selected amino acids

The separation of amino acid (AA) enantiomers shows significance for chemistry, food, and biology, but remains challenging due to their similar properties. A promising nanoporous chiral covalent organic framework (COF) as a stationary phase for high-performance liquid chromatography (HPLC) suffers from the irregularity and widely distributed particle size of the chiral COF. Herein, we show the facile preparation of a chiral COF-monolith as a stationary phase for HPLC enantiomeric separation of AAs via orthogonal experiments. The CTzDa-monolith is prepared by the incorporation of the model chiral COF named CTzDa into the porous poly(ethylene dimethacrylate-co-methacrylate) monolith and reveals great permeability and mechanical stability. The corresponding CTzDa-monolithic column gives better chiral HPLC separation of AAs than the commercial Poroshell 120 chiral-T column. Thermal dynamic analysis and molecular docking calculations imply the involvement of stereoscopic hydrogen, π-π, and van der Waals interactions between the CTzDa and AAs during HPLC enantioseparation. The facile incorporation of the chiral COF into the porous monolith will promote the potential of a chiral COF as a stationary phase for HPLC.

Hydroxyapatite surface-functionalized monolithic column for selective in-tube solid phase microextraction of zoleronic acid and risedronic acid

To date, hydroxyapatite (HAP) based monoliths were mainly fabricated by directly doping of HAP, which suffered from less effective coverage of HAP. Herein, a HAP surface-functionalized monolithic column (HAP@PDA@UF) has been prepared by in-situ biomineralization and applied as sorbent for selective in-tube solid phase microextraction of zoleronic acid and risedronic acid. A polydopamine coating was first generated on the surface of the parent urea-formaldehyde resin monolith; and then HAP microcrystals were further grew on the polydopamine coating to achieve this preparation. SEM, EDAX, FTIR, XPS and mercury intrusion method were utilized for the characterization of the HAP@PDA@UF monolith, and provided evidences of this successful preparation. The selective extraction mechanism of the HAP@PDA@UF monolith was investigated by the optimization of methanol percentage in the sampling solution, phosphate concentration in the eluent. Other crucial factors, including sampling and elution flow rate, and collection time span, were also optimized for the desired SPME performance. Under the optimal conditions, the proposed method showed low LODs of 0.1 μg/mL, satisfactory recoveries of 79.6%-92.5% with RSDs less than 2.7%, and good reproducibility with RSD less than 6.9%, which demonstrated the excellent application of the HAP@PDA@UF monolith, and its potential as a promising selective sorbent for bisphosphonates.

Benzoic acid-modified monolithic column for separation of hydrophilic compounds by capillary electrochromatography with high content of water in mobile phase

Hydrophilic column combined with mobile phase containing high content of water is a green method for the separation of polar compounds, but there are few related studies, and the separation efficiency and performance of existing columns still needs to be improved. In this work, a novel monolithic column for separation of hydrophilic compounds under both high water content and HILIC condition, was prepared by in-situ polymerization using 4-vinylbenzoic acid (VBA) and 1-(Acryloyloxy)-3-(methacryloyloxy)-2-propanol (AMAP) as functional monomers. The poly(VBA-co-AMAP) monolithic column showed good separation performance towards various polar compounds under different chromatographic conditions based on the π-interaction, hydrophobic and hydrogen bonding interactions provided by 4-vinylbenzoic acid functional monomer. The highest column efficiency for adenine was over 2.15 × 10⁵ plates m^-1 (theoretical plate, N). In addition, the monolith showed good stability and reproducibility, the relative standard deviations (RSDs) of retention times within days (n = 5), between days (n = 5), between columns (n = 3) and between batches (n = 3) were 0.47-1.13%, 1.20-2.68%, 0.59-1.78% and 1.54-3.60%, respectively. This novel type of monolith has great application potential in the separation of hydrophilic compounds.

Development of acidic phospholipid containing immobilized artificial membrane column to predict drug-induced phospholipidosis potency

Drug-induced phospholipidosis (DIPLD) represents a big concern for both regulatory authorities and pharmaceutical companies in drug discovery. Many researches pointed out that the negatively charged intralysosomal lipids play an important role in the formation of DIPLD. To better mimic this negatively charged lipid surface, a novel immobilized artificial membrane (IAM) column was prepared via in situ copolymerization of 12-methacryloyl n-dodecylphosphocholine (MDPC) and 12-methacryloyl n-dodecylphosphoric acid (MDPA). By introducing MDPA, the surface of the resulting monolithic column can be maintained negatively charged over a broad pH range. Scanning electron microscopy, elemental analysis and nano-HPLC experiments were carried out to characterize the physicochemical properties and chromatographic performance of the obtained monolithic IAM column. The results of ζ-potential and retention mechanism studies indicate that both hydrophobic and electrostatic interactions contribute greatly to the retention of cation analytes owing to the existence of the negatively charged MDPA under acidic conditions. To better assess the DIPLD potency of drug, the molar ratio between MDPC and MDPA in the monolithic column was carefully optimized. The results show that the poly(MDPC₇₀PA₃₀-co-EDMA) column has the best predictability with only two false-positives (donepezil, flecainide) in qualitative analysis of 61 drugs.

Preparation of monolithic polymer-magnetite nanoparticle composites into poly(ethylene-co-tetrafluoroethylene) tubes for uses in micro-bore HPLC separation and extraction of phosphorylated compounds

This paper describes the fabrication of a novel microbore monolithic column modified with magnetite nanoparticles (MNPs) prepared in a poly(ethylene-co-tetrafluoroethylene) (EFTE) tubing, and its application as stationary phase for the chromatographic separation of phosphorylated compounds. In order to obtain the composite column, a two-step procedure was performed. The formation of a glycidyl methacrylate-based monolith inside the activated ETFE tube was firstly carried out. Then, two incorporation approaches of MNPs in monoliths were investigated. The generic polymer was modified with 3-aminopropyltrimethoxysilane (APTMS) to be subsequently attached to MNP surfaces. Alternatively, APTMS-coated MNPs were firstly prepared and subsequently used for attachment onto the monolith surface through reaction of epoxy groups present in the generic monolith. This last strategy gave a reproducible layer of MNPs coated onto the polymer monolith as well as robust and permeable chromatographic columns. The retention behaviour of this MNP-based composite monolithic column was studied by using small phosphorylated compounds (adenosine phosphates). It was found that the retention of model analytes was ruled by partitioning and adsorption HILIC mechanisms. The columns also exhibited satisfactory performance in the separation of these target compounds, showing good chromatographic behaviour after two months of continued use. These composite monolithic columns were also successfully applied to the extraction of a tryptic digest of β-casein.

Nanoparticle-based polyacrylonitrile monolithic column for highly efficient micro solid-phase extraction of carotenoids and vitamins in human serum

In this work, a biocompatible monolithic column based micro-solid-phase extraction (µ-SPE) method was developed for biological fluid analysis. A novel nanoparticle-based polyacrylonitrile monolithic column (C30 NP-PMC) was fabricated by incorporating triacontyl (C30) modified silica nanoparticles (NPs) into the polyacrylonitrile monolithic matrix through thermally induced phase separation. With efficient mass transfer and sorption capacity, C30 NP-PMC exhibited outstanding performance for the extraction of carotenoids and fat-soluble vitamins (FSVs) from human serum samples, superior to commercial C18 cartridges as well as liquid-liquid extraction (LLE) method. Under optimal conditions, the proposed µ-SPE method coupled with high-performance liquid chromatography-diode array detection (HPLC-DAD) achieved satisfactory limits of detection (LODs) (1.5-75.0 ng/mL) and good recoveries (85.0-106.5 %) with relative standard deviations (RSDs) of less than 12.1% by consuming lower sorbent (35.0 mg) and organic solvent (0.8 mL). Successful application of the developed method demonstrated the great potential of such monolithic sorbents for efficient isolation and preconcentration of trace analytes from blood samples.

Determination of bisphosphonates anti-resorptive properties based on three forms of ceramic materials: Sorption and release process evaluation

There is a strong need to search for more effective compounds with bone anti-resorptive properties, which will cause fewer complications than commonly used bisphosphonates. To achieve this goal, it is necessary to search for new techniques to characterize the interactions between bone and drug. By studying their interaction with hydroxyapatite (HA), this study used three forms of ceramic materials, two of which are bone-stimulating materials, to assess the suitability of new active substances with anti-resorptive properties. In this study, three methods based on HA in loose form, polycaprolactone/HA (a polymer-ceramic materials containing HA), and polymer-ceramic monolithic in-needle extraction (MINE) device (a polymer inert skeleton), respectively, were used. The affinity of risedronate (a standard compound) and sixteen aminomethylenebisphosphonates (new compounds with potential antiresorptive properties) to HA was defined according to the above-mentioned methods. Ten monolithic materials based on 2-hydroxyethyl methacrylate/ethylene dimethacrylate are prepared and studied, of which one was selected for more-detailed further research. Simulated body fluids containing bisphosphonates were passed through the MINE device. In this way, sorption-desorption of bisphosphonates was evaluated using this MINE device. The paper presents the advantages and disadvantages of each technique and its suitability for assessing new active substances. All three methods allow for the selection of several compounds with potentially higher anti-resorptive properties than risedronate, in hope that it reflects their higher bone affinity and release ability.

3D printed fluidic platform with in-situ covalently immobilized polymer monolithic column for automatic solid-phase extraction

In this work, 3D stereolithographic printing is proposed for the first time for the fabrication of fluidic devices aimed at in-situ covalent immobilization of polymer monolithic columns. Integration in advanced flow injection systems capitalized upon programmable flow was realized for fully automatic solid-phase extraction (SPE) and clean-up procedures as a 'front-end' to on-line liquid chromatography. The as-fabricated 3D-printed extraction column devices were designed to tolerate the pressure drop of forward-flow fluidic systems when handling large sample volumes as demonstrated by the determination of anti-microbial agents, plastic additives and monomers as models of emerging contaminants (4-hydroxybenzoic acid, methylparaben, phenylparaben, bisphenol A and triclosan). Decoration of the monolithic phase with gold nanoparticles (AuNPs) was proven most appropriate for the enrichment of phenolic-type target compounds. In particular, the absolute recoveries for the tested analytes ranged from 73 to 92% both in water and saliva samples. The 3D printed composite monolith showed remarkable analytical features in terms of loading capacity (2 mg g-1), breakthrough volume (10 mL), satisfactory batch-to-batch reproducibility (<9% RSD), and easy on-line coupling of the SPE device to HPLC systems. The fully automatic 3D-printed SPE-HPLC hyphenated system was also exploited for the on-line extraction, matrix clean-up and determination of triclosan in 200 μL of real saliva samples.

Strong hydrophilic monolithic column functionalized with amphiphilic benzyl quinine for capillary electrochromatography and application in pharmaceutical analysis

An innovative strong hydrophilic organic polymer monolithic column of poly(N-benzylquininium chloride-co-1, 3, 5-triacryloylhexahydro-1, 3, 5-triazine) (poly(NBQ-co-TAT)) has been successfully synthesized through in situ copolymerization for capillary electrochromatography. The amphiphilic monomer NBQ and the strong polar cross-linker TAT are firstly used in hydrophilic electrochromatography by taking advantage of the exhibition of hydrophilicity at lower levels of organic solvent and ease formation of porous structure. The monolithic column poly(NBQ-co-TAT) shows powerful hydrophilic selectivity with mobile phase containing more than 60% organic solvent. The introduction of NBQ and TAT enlarges the sources of functional monomers and cross-linkers for HILIC. Due to the presence of the positively charged group in NBQ, an anodic electroosmotic flow is generated with the change of pH values from 2.0 to 12.0. The monolithic column was used for the separations of thioureas, phenols, xanthines, nucleobases, acidic substances and pharmaceuticals. The highest column efficiency for N, N'-dimethylthiourea is 1.15 × 10⁵ N m^-1. The application of the monolithic column for a real sample, cytochrome C digestion indicates its great potential in practical application.

A double-recognized aptamer-molecularly imprinted monolithic column for high-specificity recognition of ochratoxin A

In this study, a double-recognized aptamer-molecularly imprinted monolithic column (Apt-MIP monolithic column) was prepared by introducing both aptamer and MIP to reduce non-specific adsorption. Its preparation parameters such as the time of photo-initiation, the dosage of photo-initiator and the concentration of aptamer were investigated in detail. The recovery ratios of ochratoxin A (OTA) to ochratoxin B (OTB) on Apt-MIP monolithic column, Apt monolithic column and MIP monolithic column were 116.1, 40.8 and 69, respectively. Even if the concentration of OTB was 10 times that of OTA, the recovery of OTB was only about 2.9%. Applied to beer samples, the prepared Apt-MIP monolithic column drastically resisted background adsorption and the high-specificity recognition for OTA was obtained with the recoveries of 95.5-105.9%. This work provided a simple and effective method to selectively identify OTA from complex samples.

One-pot preparation of zwitterionic sulfoalkylbetaine monolith for rapid and efficient separation of lysozyme from egg white

A porous zwitterionic monolithic column was prepared to rapidly and efficiently separate lysozyme from egg white. The monolith was synthesized in a stainless steel HPLC column (5 cm × 4.6 mm i.d.) by in-situ thermal initiated co-polymerization of N,N-dimethyl-N-methacryloxyethyl-N-(3-sulfopropyl) ammonium betaine (MSA) and ethylene dimethacrylate (EDMA). Due to the combination of quaternary ammonium and sulfonic groups on the monolithic matrix in one-pot process, the hydrophobic carbon chain and hydrophilic radical were obtained, which provided multiple driving forces for neutral, basic and acidic analytes, thus mix-mode chromatography mechanism contributed to the retention of different charged proteins. Properties such as composition, morphology and stability of the MSA-co-EDMA monolithic column were characterized by various analytical methods and the results showed that the monolith has large through-pores, good hydrophilicity and permeability. The effects of mobile phase pH and ionic strength on proteins were investigated, drawing the conclusion that the main adsorption and elution mechanism of lysozyme on MSA-co-EDMA monolith was electrostatic interaction, while those of other proteins included hydrophobic, hydrophilic and electrostatic interactions. Therefore, efficient separation of lysozyme and other proteins could be successfully achieved by switching the pH of mobile phase. Lysozyme can be adsorbed using 20 mmol/L phosphate buffer (pH 7.0) and eluted with 20 mmol/L phosphate buffer (pH 2.0). To prove the practicality of the monolithic column, it was also applied in the separation of lysozyme in egg white, which means the work has the potential for further development in proteome analysis of real biological samples.

An organic polymer monolith modified with an amino acid ionic liquid and graphene oxide for use in capillary electrochromatography: application to the separation of amino acids, β-blockers, and nucleotides

The preparation of an organic polymer monolithic column modified with an amino acid ionic liquid and graphene oxide (AAIL-GO) and its application to capillary electrochromatography (CEC) was described. The AAIL tetramethylammonium-L-arginine was bonded to a monolithic column that was previously modified with graphene oxide by using an hydrochloride/N-hydroxysuccinimide coupling reaction. The morphology of a poly(glycidyl methacrylate-co-ethylene dimethacrylate) monolith was examined by scanning electron microscopy. The incorporation of AAIL and graphene oxide was detected by infrared spectroscopy and elemental analysis. The resulting monolithic column produced a strong and stable electroosmotic flow from the anode to the cathode in the pH range from 3 to 9. Compared with a column modified with AAIL or graphene oxide only, the AAIL-GO-modified column has a better separation ability for amino acids, β-blockers, and nucleotides (the resolution of three amino acids: 2.231 and 2.036, β-blockers: 2.779 and 2.470 and nucleotides: 8.345 and 3.321). Molecular modeling was applied to demonstrate the separation mechanism of small molecules which showed a good support for experimental results. Graphical abstract Schematic representation of capillary electrochromatography (CEC) systems with an amino acid ionic liquid-graphene oxide modified organic polymer monolithic column as stationary phases for separation of amino acids, β-blockers, and nucleotides.

Hydroxyapatite-embedded monolithic column for selective on-line solid-phase extraction of adenosine triphosphate and its phosphorylated metabolites

A novel hydroxyapatite-embedded monolithic column has been facilely prepared in a stainless-steel column with inner diameter of 2.1 mm by the strong adhesion of urea-formaldehyde (UF) resin and exploited as a sorbent for selective on-line solid-phase extraction (on-line SPE) of adenosine triphosphate and its phosphorylated metabolites. The composition for this preparation, including the amount of hydroxyapatite nanopowders and the porogen were investigated to obtain a suitable monolith with large surface area and satisfactory permeability. Owing to anion exchange interaction of hydroxyapatite and hydrophilic interaction of UF monolithic matrix, the prepared monolith showed good extraction efficiency and selectivity towards these phosphorylated analytes. Several parameters for on-line SPE, including ACN percentage in the sampling solution, collection time span, salt concentration of the eluent, sampling and elution flow rate, were optimized with respect to the extraction efficiencies of the target compounds. Under the optimized conditions, the LODs of the analytes were in the range of 0.01-0.04 μg/g, the recoveries in the spiked samples ranged from 78.3%-92.5% with RSDs <4.7%. Due to the excellent extraction ability towards phosphorylated compounds in practical samples, a simple on-line SPE-HPLC method using hydroxyapatite-embedded monolith as sorbent has been proposed for monitoring freshness of grass carp.

Green analytical chromatographic assay method for quantitation of cyclobenzaprine in tablets, spiked human urine and in-vitro dissolution test

Cyclobenzaprine hydrochloride, a skeletal muscle relaxant has been determined using an ecofriendly micellar HPLC method in its pure form and tablets. The chromatographic determination was performed using C₈ monolithic column (100mm×4.6mm i.d., 5μm particle size) and micellar eluent which was composed of sodium dodecyl sulfate (0.15M), n-propanol (15%), 0.02M orthophosphoric acid (pH 4.5) and 0.3% triethylamine using UV detection of effluent was set at 225nm. The calibration plot showed good linearity over concentration range from 2-40μg/mL. The assay results were statistically validated for linearity, accuracy, precision and specificity according to ICH guidelines. Additionally, regarding USP guidelines, the uniformity of tablets content and in-vitro dissolution test of the tablets was tested using the proposed method. Simple and rapid applicability of the developed method allowed determination of the drug in its pure and tablet dosage forms. Moreover, the major advantage of micellar HPLC technique is to determine the drug in biological fluids without prior extraction steps. Depending on this, the estimation of cyclobenzaprine in spiked human urine was so simple without traditional tedious procedures. The proposed method offers the advantages of sensitivity and simplicity in addition to short analysis time which didn't exceed 6 minutes.

Analysis of Evodiae Fructus by capillary electrochromatography-mass spectrometry with methyl-vinylimidazole functionalized organic polymer monolilth as stationary phases

Evodiae Fructus is used as a traditional Chinese medicine for the treatment of several kinds of diseases with its bioactive constituents. In this study, a capillary electrochromatography-mass spectrometry (CEC-MS) method was developed to determine three bioactive compounds including evodiamine, rutaecarpine and limonin in Evodiae Fructus fruit. Home-developed monolithic columns with methyl-vinylimidazole functionalized organic polymer monolilth as stationary phases were used in CEC-MS with excellent separation selectivity and high efficiency. The CEC-MS methods provided 4-16 folds improvement of LODs when compared with CEC-UV method. The conditions, which could affect separation efficiency and detection sensitivity, were optimized. Under optimum conditions, baseline separation with high detection sensitivity was obtained. The method showed good linearity (R² >0.99) of 0.8-160 μg mL^-1 with low limits of detection of 0.15-0.31 μg mL^-1. Relative standard deviations of migration time and relative peak areas were <13.89%. Recoveries of evodiamine, rutaecarpine and limonin in Evodiae Fructus fruit were tested and calculated, which ranged from 102% to 113%. Finally, the three bioactive compounds in Evodiae Fructus herb samples from different regions were analyzed and studied. It has been demonstrated that the developed method has great potential for quality control of Evodiae Fructus herb.

Advances in capillary electro-chromatography

Capillary electrochromatography (CEC) is a micro-scale separation technique which is a hybrid between capillary electrophoresis (CE) and liquid chromatography (LC). CEC can be performed in packed, monolithic and open-tubular columns. In recent three years (from 2016 to 2018), enormous attention for CEC has been the development of novel stationary phases. This review mainly covers the development of novel stationary phases for open-tubular and monolithic columns. In particular, some biomaterials attracted increasing interest. There are no significant breakthroughs in technology and principles in CEC. The typical CEC applications, especially chiral separations are described.

Fabrication of a ferrocene-based monolithic column with a network structure and its application in separation of protein and small molecules

A novel ferrocene-based monolith with a network structure was fabricated via in situ free radical polymerization using vinyl ferrocene as the co-monomer within a stainless-steel column (50 × 4.6 mm i.d.) for the separation of proteins from complex bio-samples, taking merit of the specific absorption of ferrocene to protein, including human plasma, egg white, and standard proteins. The morphology and pore size distribution indicate that the optimized monolith has a relatively uniform structure with the network. The results showed that 26 fractions were separated from human plasma, and the column efficiency of the aromatic small molecule, naphthalene, was up to 30,560 plates m^-1. The homemade monolith showed excellent selectivity for intact proteins, mainly depending on the hydrophobic chromatography mechanism of ferrocene. In addition, the electrostatic interaction and hydrogen-bond interaction were the additional interactions in the chromatographic separation owing to the sandwich structure of ferrocene present in the monolithic column.

Evaluation of meter-long monolithic columns for selected reaction monitoring mass spectrometry

Proteome is extremely complex as many proteins with a large dynamic range are involved. Nano-liquid chromatography/mass spectrometry-based proteomics has made it possible to separate and identify thousands of proteins in one shot. Although the number of identified proteins in proteomics has significantly improved, it is necessary to increase detection sensitivity to clearly identify low-abundant proteins. In this study, we developed meter-long monolithic columns with a small inner diameter and applied them to selected reaction monitoring-based proteomics for improving proteomic detection sensitivity. Bovine serum albumin tryptic digests were analyzed with optimized selected reaction monitoring methods, and separation efficiency and detection sensitivity in each monolithic column were evaluated. As a result, peak capacity increased by about 1.8-fold and peak area of peptide levels increased by about 2.3-fold. Although flow rate was reduced during analysis with columns of a smaller inner diameter, the peak area reproducibility was maintained. These data displayed the value of meter-long monolithic columns with small inner diameter for selected reaction monitoring-based proteomics.

Silver nanoparticles-coated monolithic column for in-tube solid-phase microextraction of monounsaturated fatty acid methyl esters

Based on our developed sodium hyaluronate-functionalized urea-formaldehyde (HA-UF) monolith, a silver nanoparticles-coated monolithic column has been fabricated via the interaction between silver nanoparticles (Ag NPs) and HA. The successful coating of Ag NPs on the parent monolith was proven by SEM, EDAX, UV-vis spectrum and XPS. Nitrogen adsorption desorption isotherms and Barret-Joyner-Halenda (BJH) pore size distributions of the parent and resultant monolith were also performed. Due to the Ag⁺-like affinity interaction caused by the contact of unsaturated compounds and Ag NPs, the Ag NPs-coated monolith showed satisfactory extraction efficiency towards these compounds, and was applied for in-tube solid-phase microextraction (SPME) of monounsaturated fatty acid methyl esters (MUFAMEs). Several factors for in-tube SPME, such as ACN percentage in the sampling solution, elution volume, sampling and elution flow rate, were investigated with respect to the extraction efficiency of model MUFAMEs. Under the optimized SPME conditions, a simple in tube SPME-Ag⁺-HPLC method for detection of model MUFAMEs has been proposed, the limits of detection (LODs) were less than 5.2 μg/kg, and the recoveries of spiked French fry samples were ranged from 86.6% to 96.1% with relative standard deviations (RSDs) less than 5.2%. This study provided an Ag NPs-coated monolith with good reproducibility and repeatable extraction performance, and developed an efficient method for in-tube SPME of MUFAMEs in practical food samples.

Ionic liquid-copolymerized monolith incorporated with zeolitic imidazolate framework-8 as stationary phases for enhancing reversed phase selectivity in capillary electrochromatography

A novel ionic liquid (1-allyl-methylimidazolium chloride, AlMeIm⁺Cl^-) polymer monolith poly(ionic liquid-co-ethylene dimethacrylate) incorporated with zeolitic imidazolate framework-8 (ZIF-8-poly(IL-co-EDMA)) was firstly synthesized as stationary phases of monolithic column for capillary electrochromatography by one-step copolymerization. Incorporation of ZIF-8 into ionic liquid polymer monolith evidently enhanced the separation selectivity for four alkylbenzenes in reversed phase capillary electrochromatography (CEC), due to the synergistic effect derived from the same imidazole ring structure of ionic liquid and organic ligands of ZIF-8. Meanwhile, electroosmotic flow (EOF) was generated by ionic liquid in a wide range of pH values from 2.0 to 12.0. The resultant monolithic columns were characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR). The results indicated that the prepared monolithic columns had good permeability and mechanism stability. The resultant monolithic columns were applied for the separation of neutral compounds, anilines and phenols. The highest column efficiency was 2.07 × 10⁵ plates m^-1 (theoretical plates, N) for toluene. Under optimal conditions, reproducibility was obtained with relative standard deviations (RSDs) of the retention time for run-to-run, day-to-day, column-to-column and batch-to-batch were in the range of 1.58 - 3.19%, 1.92 - 3.87%, 3.84 - 4.96% and 2.63 - 4.33%, respectively. Incorporation ZIF-8 into ionic liquid polymer monolith was a promising way for the application of new materials in the fabrication of novel monolithic columns.

Monolith columns for liquid chromatographic separations of intact proteins: A review of recent advances and applications

In this article we survey 256 references (with an emphasis on the papers published in the past decade) on monolithic columns for intact protein separation. Protein enrichment and purification are included in the broadly defined separation. After a brief introduction, we describe the types of monolithic columns and modes of chromatographic separations employed for protein separations. While the majority of the work is still in the research and development phase, papers have been published toward utilizing monolithic columns for practical applications. We survey these papers as well in this review. Characteristics of selected methods along with their pros and cons will also be discussed.

Determination of Ochratoxin A traces in foodstuffs: Comparison of an automated on-line two-dimensional high-performance liquid chromatography and off-line immunoaffinity-high-performance liquid chromatography system

Automated on-line two-dimensional high-performance liquid chromatography method (2D-HPLC) is proposed to determine Ochratoxin A (OTA) in food samples as an alternative to OTA immunoaffinity column (IAC). An on-line 2D-HPLC system is designed for the analysis of OTA using an affinity-based monolithic column in the first dimension and reversed-phase C18 column in the second dimension. Initially, optimal OTA separation efficiency is determined through traditional HPLC system consisting of a P(HEMAPA) monolithic column coupled with HPLC system. Secondly, after providing optimum conditions, OTA determination was investigated through the 2D-HPLC system. According to results, 2D-HPLC system showed good linearity in the range 0.5 to 20 ng/mL with limit of detection (LOD) and limit of quantification (LOQ) values of 21.2 pg/mL and 64.3 pg/mL, respectively. The P(HEMAPA)-4 monolithic column displayed good recovery of OTA ranging from 104.34% to 107.33%. Relative standard deviations (RSD) varied in the range 0.21% to 1.31% thus indicating the efficiency of P(HEMAPA)-4 monolithic column developed for OTA.

Green synthesis of monolithic column incorporated with graphene oxide using room temperature ionic liquid and eutectic solvents for capillary electrochromatography

In this work, a hybrid monolith incorporated with graphene oxide (GO) was prepared in the first time with binary green porogens of deep eutectic solvents (DESs) and room temperature ionic liquids (RTILs). GO was modified with 3-(trimethoxysilyl) propylmethacrylate (γ-MPS), and the resultant GO-MPS can be incorporated into poly (methacrylic acid-co-butylmethacrylate-co-ethylene glycol dimethacrylate) monoliths covalently. A hybrid monolithic column with high permeability and homogeneity can be achieved due to good dispersion of GO-MPS in the green solvents. The GO-MPS incorporated monolith was characterized by transmission electron microscopy, scanning electron microscopy, thermogravimetric analysis and nitrogen adsorption tests. The separation of small organic molecules of alkylphenones and alkylbenzenes was used to evaluate the performance of GO-MPS grafted monolith. The GO-MPS grafted monolith displayed the maximum column efficiency of 147,000 plates/m, about twice higher than the GO-free monolith. In addition, all of the retention and selectivity of small molecules of alkylphenones and alkylbenzenes increased due to the addition of GO-MPS. The results demonstrated that the use of DESs and RTILs is a powerful approach for the preparation of GO incorporated polymer monoliths. The monolith was further applied to the separation of tryptic digests from bovine serum albumin, and the result indicated its potential in the analysis of some complex samples.

RpeakChrom: Novel R package for the automated characterization and optimization of column efficiency in high-performance liquid chromatography analysis

Characterization of chromatographic columns using the traditional van Deemter method is limited by the necessity of calculating extra-column variance, issue particularly relevant when modeling asymmetrical peaks eluted from monolithic columns. A novel R package that implements Parabolic Variance Modified Gaussian approach for accurate peak modeling, van Deemter equation and two alternatives approaches, based on van Deemter, has been developed to calculate the height equivalent to a theoretical plate (HETP). To assess package capabilities conventional packed reverse-phase and monolithic HPLC columns were characterized. Peaks eluted from the monolithic column showed a high value of factor asymmetry due, in part, to the contribution of extra-column factors. Such deviation can be circumvented by the two alternatives approaches implemented in the R-package. Furthermore, increased values of eddy diffusion and mass transfer kinetics terms in HETP were observed for the packed column, while accuracy was below 9% in all cases. These results showed the usefulness of the R-package for both modeling chromatographic peaks and assessing column efficiency. The RpeakChrom package could become a helpful tool for testing new stationary phases during column development and to evaluate column during its lifetime. This R tool is freely available from CRAN (https://CRAN.R-project.org/package=RpeakChrom).

Rapid simultaneous determination of indacaterol maleate and glycopyrronium bromide in inhaler capsules using a validated stability-indicating monolithic LC method

Background

Chronic obstructive pulmonary disease (COPD) is a major cause of morbidity and mortality worldwide. A combination of indacaterol maleate with glycopyrronium bromide has recently been approved as a once-daily maintenance therapy in patients with COPD. The very low dose (μg level/capsule) renders the analysis of such products challenges. This study reports for the first time about HPLC method for the quality control of such combination and it is a stability indicating at the same time.

Results

A rapid, simple, precise and reproducible HPLC method was developed and validated for simultaneous determination of indacaterol maleate and glycopyrronium bromide using tenoxicam as an internal standard. The chromatographic separation was achieved on an onyx monolithic C18 column (100 × 4.6 mm) using a mobile phase consisting of acetonitrile and 30 mM phosphate buffer (pH 3.5) (30:70, v/v), run at a flow rate of 2 mL/min with UV detection at 210 nm. The total analysis time was less than 3 min. The HPLC method was validated for linearity, limits of detection and quantitation, precision, accuracy, system suitability and robustness. Calibration curves were obtained in the concentration ranges of 1–44 µg/mL for indacaterol maleate and 0.5–20 µg/mL for glycopyrronium bromide. Stability tests were done through exposure of the analyte solution for different stress conditions and the results indicate no interference of degradants with HPLC method.

Conclusions

The method was successfully applied for the quantitative analysis of indacaterol maleate and glycopyrronium bromide both individually and in a combined pharmaceutical inhaler capsules to support the quality control and to assure the therapeutic efficacy of the two drugs. The simple procedure involved in sample preparation and the short run-time added the important property of high throughput to the method. Graphical abstract

Off-line mixed-mode liquid chromatography coupled with reversed phase high performance liquid chromatography-high resolution mass spectrometry to improve coverage in lipidomics analysis

The confident identification and in-depth profiling of molecular lipid species remain to be a challenge in lipidomics analysis. In this work, an off-line two-dimensional mixed-mode and reversed-phase liquid chromatography (RPLC) method combined with high-field quadrupole orbitrap mass spectrometer (Q Exactive HF) was developed to profile lipids from complex biological samples. In the first dimension, 22 different lipid classes were separated on a monolithic silica column with elution order from neutral to polar lipids. A total of 13 fractions were collected and run on a RPLC C30 column in the second dimension for further separation of the lipid molecular species based on their hydrophobicity, with the elution order being determined by both the length and degree of unsaturation in the fatty-acyl chain. The method was applied to analyze lipids extracted from rat plasma and rat liver. Fatty acid methyl ester analysis by gas chromatography-mass spectrometry was used to identify the fatty acyls from total lipid extracts, which provided a more confident identification of the lipid species present in these samples. More than 800 lipids were identified in each sample and their molecular structures were confidentially confirmed using tandem mass spectrometry (MS/MS). The number of lipid molecular species identified in both rat plasma and rat liver by this off-line two-dimensional method is approximately twice of that by one-dimensional RPLC-MS/MS employing a C30 column. This off-line two-dimensional mixed-mode LC-RPLC-MS/MS method is a promising technique for comprehensive lipid profiling in complex biological matrices.

Green approach using monolithic column for simultaneous determination of coformulated drugs

Green chemistry and sustainability is now entirely encompassed across the majority of pharmaceutical companies and research labs. Researchers' attention is careworn toward implementing the green analytical chemistry principles for more eco-friendly analytical methodologies. Solvents play a dominant role in determining the greenness of the analytical procedure. Using safer solvents, the greenness profile of the methodology could be increased remarkably. In this context, a green chromatographic method has been developed and validated for the simultaneous determination of phenylephrine, paracetamol, and guaifenesin in their ternary pharmaceutical mixture. The chromatographic separation was carried out using monolithic column and green solvents as mobile phase. The use of monolithic column allows efficient separation protocols at higher flow rates, which results in short time of analysis. Two-factor three-level experimental design was used to optimize the chromatographic conditions. The greenness profile of the proposed methodology was assessed using eco-scale as a green metrics and was found to be an excellent green method with regard to the usage and production of hazardous chemicals and solvents, energy consumption, and amount of produced waste. The proposed method improved the environmental impact without compromising the analytical performance criteria and could be used as a safer alternate for the routine analysis of the studied drugs.

Development and validation of HPLC method with fluorometric detection for quantification of bisnaphthalimidopropyldiaminooctane in animal tissues following administration in polymeric nanoparticles

A simple, sensitive and specific high-performance liquid chromatography method for the quantification of bisnaphthalimidopropyldiaminooctane (BNIPDaoct), a potent anti-Leishmania compound, incorporated into poly(d,l-lactide-co-glycolic acid) (PLGA) nanoparticles was developed and validated toward bioanalysis application. Biological tissue extracts were injected into a reversed-phase monolithic column coupled to a fluorimetric detector (λexc=234nm, λem=394nm), using isocratic elution with aqueous buffer (acetic acid/acetate 0.10M, pH 4.5, 0.010M octanesulfonic acid) and acetonitrile, 60:40 (v/v) at a flow rate of 1.5mLmin(-1). The run time was 6min, with a BNIPDaoct retention time of 3.3min. Calibration curves were linear for BNIPDaoct concentrations ranging from 0.002 to 0.100μM. Matrix effects were observed and calibration curves were performed using the different organ (spleen, liver, kidney, heart and lung) extracts. The method was found to be specific, accurate (97.3-106.8% of nominal values) and precise for intra-day (RSD<1.9%) and inter-day assays (RSD<7.2%) in all matrices. Stability studies showed that BNIPDaoct was stable in all matrices after standing for 24h at room temperature (20°C) or in the autosampler, and after three freeze-thaw cycles. Mean recoveries of BNIPDaoct spiked in mice organs were >88.4%. The LOD and LOQ for biological matrices were ≤0.8 and ≤1.8nM, respectively, corresponding to values ≤4 and ≤9nmolg(-1) in mice organs. The method developed was successfully applied to biodistribution assessment following intravenous administration of BNIPDaoct in solution or incorporated in PLGA nanoparticles.

Exoproteome analysis of Clostridium cellulovorans in natural soft-biomass degradation

Clostridium cellulovorans is an anaerobic, cellulolytic bacterium, capable of effectively degrading various types of soft biomass. Its excellent capacity for degradation results from optimization of the composition of the protein complex (cellulosome) and production of non-cellulosomal proteins according to the type of substrates. In this study, we performed a quantitative proteome analysis to determine changes in the extracellular proteins produced by C. cellulovorans for degradation of several types of natural soft biomass. C. cellulovorans was cultured in media containing bagasse, corn germ, rice straw (natural soft biomass), or cellobiose (control). Using an isobaric tag method and a liquid chromatograph equipped with a long monolithic silica capillary column/mass spectrometer, we identified 372 proteins in the culture supernatant. Of these, we focused on 77 saccharification-related proteins of both cellulosomal and non-cellulosomal origins. Statistical analysis showed that 18 of the proteins were specifically produced during degradation of types of natural soft biomass. Interestingly, the protein Clocel_3197 was found and commonly involved in the degradation of every natural soft biomass studied. This protein may perform functions, in addition to its known metabolic functions, that contribute to effective degradation of natural soft biomass.

A one-step preparation method of monolithic enzyme reactor for highly efficient sample preparation coupled to mass spectrometry-based proteomics studies

Mass spectrometry (MS) coupled to sample preparation and separation techniques has become a primary tool for proteomics studies. However, due to sample complexity, it is often challenging to achieve fast and efficient sample preparation prior to MS analysis. In recent decades, monolithic materials have been developed not only as chromatographic media, but also as efficient solid supports for immobilizing multiple types of affinity reagents. Herein, the N-acryloxysuccinimide-co-acrylamide-co-N,N'-methylenebisacrylamide (NAS-AAm-Bis) monolith was fabricated within silanized 200 μm i.d. fused-silica capillaries and was used as an immobilized enzyme reactor (IMER). The column was conjugated with trypsin/Lys-C and Lys-N enzymes to allow enzymatic digestions to occur while protein mixture was loaded onto the IMER column followed by MS-based proteomics analysis. Similar MS signal and protein sequence coverage were observed using protein standard bovine serum albumin (BSA) compared to in-solution digestion. Furthermore, mouse serum, yeast, and human cell lysate samples were also subjected to enzymatic digestion by both IMER (in seconds to minutes) and conventional in solution digestion (overnight) for comparison in large-scale proteomics studies. Comparable protein identification results obtained by the two methods highlighted the potential of employing NAS-based IMER column for fast and highly efficient sample preparation for MS analysis in proteomics studies.

Elucidation of the recognition mechanisms for hemicellulose and pectin in Clostridium cellulovorans using intracellular quantitative proteome analysis

Clostridium cellulovorans is an anaerobic, cellulolytic bacterium, capable of effectively degrading and metabolizing various types of substrates, including cellulose, hemicellulose (xylan and galactomannan), and pectin. Among Clostridia, this ability to degrade and metabolize a wide range of hemicellulose and pectin substrates is a unique feature; however, the mechanisms are currently unknown. To clarify the mechanisms of hemicelluloses and pectin recognition and metabolism, we carried out a quantitative proteome analysis of C. cellulovorans cultured with these substrates. C. cellulovorans was cultured in the medium of glucose (control), xylan, galactomannan (Locus bean gum, LBG), or pectin for 36 h. Xylan and galactomannan were used to search for the common recognition mechanisms of hemicellulose, and pectin was used to search for unique recognition systems in C. cellulovorans. Using an isobaric tag method and liquid chromatograph/mass spectrometer equipped with a long monolithic silica capillary column, we identified 734 intracellular proteins from all substrates. We performed KEGG analyses and cluster analyses of the resulting proteins. In the KEGG analyses, we found common degradation mechanisms for hemicellulose and pectin. In the cluster analysis corresponding to the genome analysis, we detected substrate-specific clusters that include genes involved in substrate recognition, substrate degradation, and metabolism. Combining the results of the KEGG analyses and cluster analyses, we propose the mechanisms involved in the recognition and metabolism of hemicellulose and pectin in C. cellulovorans.

Phosphatidylcholine covalently linked to a methacrylate-based monolith as a biomimetic stationary phase for capillary liquid chromatography

In this study a strategy to immobilize phospholipids onto a polymer-based stationary phase is described. Methacrylate-based monoliths in capillary format (150×0.1mm) were modified by soybean phosphatidylcholine through 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide coupling to obtain stationary phases suitable to mimic cell surface membranes. The covalent coupling reaction involves the phosphate group in phospholipids; therefore, the described methodology is suitable for all types of phospholipids. Immobilization of soy bean phosphatidylcholine on the monolith was confirmed by attenuated total reflectance Fourier transform infrared spectroscopy and gas chromatography-mass spectrometry of the fatty alcohol profile, generated upon reductive cleavage of the fatty acyl side chains of the phospholipid on the monolith surface with lithium aluminium hydride. The prepared stationary phases were evaluated through studies on the retention of low-molar mass model analytes including neutral, acidic, and basic compounds. Liquid chromatographic studies confirmed predominant hydrophobic interactions between the analytes and the synthesized stationary phase; however, electrostatic interactions contributed to the retention as well. The synthesized columns showed high stability even with fully aqueous mobile phases such as Dulbecco's phosphate-buffered saline solution.

Profiling of drug binding proteins by monolithic affinity chromatography in combination with liquid chromatography-tandem mass spectrometry

A new approach for proteome-wide profiling drug binding proteins by using monolithic capillary affinity chromatography in combination with HPLC-MS/MS is reported. Two immunosuppresive drugs, namely FK506 and cyclosporin A, were utilized as the experimental models for proof-of-concept. The monolithic capillary affinity columns were prepared through a single-step copolymerization of the drug derivatives with glycidyl methacrylate and ethylene dimethacrylate. The capillary chromatography with the affinity monolithic column facilitates the purification of the drug binding proteins from the cell lysate. By combining the capillary affinity column purification and the shot-gun proteomic analysis, totally 33 FK506- and 32 CsA-binding proteins including all the literature reported target proteins of these two drugs were identified. Among them, two proteins, namely voltage-dependent anion-selective channel protein 1 and serine/threonine-protein phosphatase PGAM5 were verified by using the recombinant proteins. The result supports that the monolithic capillary affinity chromatography is likely to become a valuable tool for profiling of binding proteins of small molecular drugs as well as bioactive compounds.

Single-step approach for fabrication of vancomycin-bonded silica monolith as chiral stationary phase

A vancomycin-bonded silica monolithic column for capillary electrochromatography (CEC) was prepared by a single-step in situ sol-gel approach. This sol-gel process incorporates a synthetic sol-gel precursor which contains a macrocyclic antibiotic, vancomycin, to form a porous silica network inside a fused-silica capillary. To avoid degradation of vancomycin during the column fabrication, a mild step was adopted into the sol-gel process. The performance of the vancomycin chiral stationary phase was investigated by CEC in both the reversed-phase mode and the normal-phase mode. The vancomycin chiral stationary phase was optimized with respect to vancomycin loading in the reversed-phase mode for chiral separation of thalidomide enantiomers. The best efficiency and resolution values of 94600plates/m and 5.79, respectively, were achieved. The optimized column was further applied to chiral separation of alprenolol enantiomers. A plate height of less than 7μm for the first eluted enantiomer of alprenolol was obtained in an aqueous mobile phase at a flow rate of 0.74mm/s. Using enantiomers of seven β-blockers and some other basic enantiomers as test analytes, separation efficiencies of up to 148100plates/m in the reversed-phase mode and up to 138100plates/m in the normal-phase mode were achieved.

Simultaneous determination of tylosin and josamycin residues in muscles, liver, eggs and milk by MLC with a monolithic column and time-programmed UV detection: application to baby food and formulae

Background

Tylosin and Josamycin are macrolide antibiotics. They are used in the treatment of pneumonia, arthritis and mastitis in cattle, and mycoplasma infections in poultry. The incorrect use of antibiotics has lead to the presence of antibiotic residues in foods. The residues cause toxic effects on consumers.

Results

A simple and sensitive method was optimized and validated for the analysis of tylosin and josamycin residues in food samples. Analytical separation was performed in less than 10 min using a RP C₁₈ monolithic column with time-programmed UV detection at 287 nm and 232 nm and a micellar solution of 0.17 M sodium dodecyl sulphate, 14% methanol and 0.3% triethylamine in 0.02 M phosphoric acid buffered at pH 4 as the mobile phase. The method was fully validated in accordance with ICH guidelines. The micellar method was successfully applied to quantitatively determine tylosin and josamycin residues in spiked chicken muscles, chicken liver, bovine muscles, liver, milk and eggs. It was also extended to the determination of tylosin and josamycin residues in chicken-based baby food and baby formulae. The compounds were separated by a monolithic column which, on account of its particular structure, could bear higher flow rates than usually found for this kind of analysis. High extraction efficiency for tylosin and josamycin was obtained without matrix interference in the extraction process and in the subsequent chromatographic determination. No organic solvent was used during the pretreatment step. Hence, it is considered an interesting technique for “green” chemistry.

Conclusion

The proposed method was validated and successfully applied for the determination of tylosin and josamycin residues in spiked chicken muscles, chicken liver, bovine muscles, liver, milk and eggs. It was also extended to the determination of tylosin and josamycin residues in chicken-based baby food and baby formulae.

Off-line hyphenation of boronate affinity monolith-based extraction with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for efficient analysis of glycoproteins/glycopeptides

Boronate affinity materials have attracted increasing attentions as sample enrichment platforms for glycoproteomic analysis in recent years. However, most of the boronate affinity materials that have already employed for proteomic analysis are suffering from apparent disadvantages, such as alkaline pH for binding, weak affinity, and relatively poor selectivity. Benzoboroxoles are a unique class of boronic acids which have showed excellent binding properties for the recognition of cis-diol-containing compounds. Recently, a 3-carboxy-benzoboroxole-functionalized monolithic column had been reported and it had exhibited the best selectivity and affinity as well as the lowest binding pH among all reported boronate affinity monolithic columns. In this study, an off-line hyphenation of this boronate affinity monolithic column-based extraction with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was developed and the powerfulness of this hyphenated approach in the analysis of glycoproteins and glycopeptides in complex samples was investigated. The approach was first applied to the analysis of glycopeptides in the tryptic digest of horseradish peroxidase (HRP). Totally 22 glycopeptides were identified. To the best of our knowledge, this is the best performance among all the boronic acid-functionalized materials. We further employed this approach to the analysis of intact proteins in human saliva. Totally 6 intact glycoproteins were successfully identified. As comparison, when the samples were analyzed without extraction, only a few glycopeptides were identified from the tryptic digest of HRP while no glycoproteins were found from the saliva samples.

Pyridinylboronic acid-functionalized organic-silica hybrid monolithic capillary for the selective enrichment and separation of cis-diol-containing biomolecules at acidic pH

Boronate affinity chromatography (BAC) is a unique means for the selective separation and enrichment of 1,2 and 1,3 cis-diol-containing compounds. However, conventional boronate affinity materials require a basic binding pH (usually≥8.5), which gives rise to not only inconvenience in operation but also the risk of degradation of labile compounds. Although the applicable pH has been expanded to 5.0 in recent years, the current boronate affinity materials still fail to meet the acidic pH end of frequently used biosamples, particularly urine (pH 4.5). In this study, we report a 3-pyridylboronic acid-functionalized organic-silica hybrid monolithic capillary that exhibited a binding pH of 4.5, the lowest so far in BAC. Such a binding pH enabled direct extraction of cis-diol-containing biomolecules such as nucleosides from urine samples without pH adjustment. The boronate affinity monolithic capillary showed enhanced affinity toward negatively charged cis-diol-containing analytes such as ribonucleotides. Moreover, it could function as an anion exchanger at acidic pH (∼2). The column was found to retain multiple compounds from urine, which can be assumed to be at least mostly if not entirely cis-diol-containing compounds.

Occurrence of deoxynivalenol in foods for human consumption from tehran, iran

The occurrence of deoxynivalenol (DON) in retail foods in Tehran (Iran) was determined using high-performance liquid chromatography technique and immunoaffinity column as the clean-up step. A method was validated for analysis of DON in rice, bread, puffed corn snack and wheat flour. The average recoveries and precision (RSD) for DON in different foods ranged 84.2-93.1% and 2.9-12.0%, respectively. A survey of DON was performed on the 72 samples of rice, bread, puffed corn snack, and wheat flour collected from Tehran retail market. The data showed that 10 samples (13.9%) out of 72 samples were contaminated with DON with the maximum level of 368.7 ng/g. The samples had contamination level lower than the maximum tolerated level of DON in foods in Iran. The total intake of DON was under the provisional maximum tolerable daily intake set for DON by the JECFA.

Rapid chromatographic determination of caseins in milk with photometric and fluorimetric detection using a hydrophobic monolithic column

Reverse-phase liquid chromatographic methods using a hydrophobic C18 monolithic column and on-line photometric and fluorimetric detection for the determination of the major casein (CN) proteins in milk are presented. The separation of αs1-CN, αs2-CN, β-CN and κ-CN was achieved in only five minutes. Fluorimetric detection enabled better analytical results than photometric detection. Thus, the dynamic ranges of the calibration graphs and detection limits obtained using fluorimetric detection were (mgmL(-)(1)): αs1-CN (0.74-10.0, 0.22), αs2-CN (0.15-10.0, 0.045), β-CN (0.68-10.0, 0.20) and κ-CN (0.21-10.0, 0.06). The analytical features of the photometric method, which does not allow the quantification of β-casein, were (mgmL(-)(1)): αs1-CN (1.5-9.0, 0.45), αs2-CN (1.4-10.0, 0.43) and κ-CN (0.4-9.0, 0.12). Precision data, expressed as relative standard deviation, ranged between 0.6% and 5.3% for the fluorimetric method and between 2.4% and 6.2% for the photometric method. Both methods were applied to the analysis of three different milk samples, obtaining recoveries in the ranges of 86.6-103.2% and 92.0-106.5% using fluorimetric and photometric detection, respectively.

Analysis of aflatoxin b1 in Iranian foods using HPLC and a monolithic column and estimation of its dietary intake

A high performance liquid chromatographic method was developed for determination of aflatoxin B1 (AFB1) in foods using a monolithic column with sample clean up on an immunoaffinity column. The method was validated for analysis of AFB1 in rice, bread, puffed corn snack, wheat flour and peanut samples. The average recoveries for AFB1 in different foods ranged from 94.4 to 102.5% with the coefficient of variation lower than 10% for all foods. Limit of detection was 0.01 ng/g. A survey of AFB1 was performed on 90 samples collected from Tehran retail market in June 2005. The results showed that none of the bread and wheat flour samples were contaminated with AFB1. The mean AFB1 levels in rice, puffed corn snack and peanut samples were 4.17, 0.11, and 1.97 ng/g, respectively. The level of contamination of 3 samples (one rice sample and two peanuts samples) to AFB1 was found to be higher than 5 ng/g. Although all food samples had mean concentration of AFB1 below the maximum tolerated level in Iran, the mean intake of AFB1 from rice was estimated 3.49 times higher than the guidance value of 1 ng AFB1/Kg body weight/day. Therefore, it is strongly recommended to monitor AFB1 in foods, especially in rice, in Iran. This is the first study on exposure assessment of Iranian population to AFB1.