Exploiting High-Resolution Mass Spectrometry for Targeted Metabolite Quantification and 13C-Labeling Metabolism Analysis

Quantification of targeted metabolites, especially trace metabolites and structural isomers, in complex biological materials is an ongoing challenge for metabolomics. In this chapter, we summarize high-resolution mass spectrometry-based approaches mainly used for targeted metabolite and metabolomics analysis, and then introduce an MS1/MS2-combined PRM workflow for quantification of central carbon metabolism intermediates, amino acids, and shikimate pathway-related metabolites. Major steps in the workflow, including cell culture, metabolite extraction, LC-MS analysis and data processing, are described. Furthermore, we adapt this new approach to a dynamic ¹³C-labeling experiment and demonstrate its unique advantage in capturing and correcting isotopomer labeling curves to facilitate nonstationary ¹³C-labeling metabolism analysis.

Cancer Exome-Based Identification of Tumor Neo-Antigens Using Mass Spectrometry

Neo-antigens expressed on tumors are targets for development of cancer immunotherapy strategies. Use of prediction algorithms to identify neo-antigens yields a significant number of peptides that must be validated in laborious and time-consuming methods; many prove to be false-positive identifications. The use of HLA peptidomics allows the isolation of the HLA-peptide complexes directly from cells and can be done on fresh tumor, patient-derived xerographs, or cell lines when the tissue sample is limited. This method can be used to identify both HLA class I and HLA class II or any different MHC from different species. Here we describe the steps to create the immune-affinity columns used from the process, the immunoprecipitation procedure, and also the isolation of the peptides that will be analyzed by mass spectrometry.

Analysis and Enantioseparation of Amino Acids by Liquid Chromatography

Enantioseparation studies of proteinogenic, non-proteinogenic, and dansyl amino acids are described herein by using liquid chromatographic techniques, i.e., HPLC and TLC. A researcher who wants to perform amino acid (AA) analysis or separate enantiomers of AAs by HPLC or TLC can follow the method. Figures included represent the actual experiments.Synthesis and application of chiral derivatizing reagents (CDRs) based on cyanuric chloride (CC) and difluorodinitrobenzene (DFDNB) have been described for AA analysis and enantioseparation by indirect approach. The methods represent pre-column derivatization of AAs and represent a good and less expensive substitute of AA analyzer. The application of commercial "Chiralplate" and use of erythromycin and L-tartaric acid have been described as chiral selector either as impregnating reagent in the stationary phase or as an additive in the mobile phase for direct enantioseparation by TLC. Application of the homemade TLC plates has also been described; the methods are successful in obtaining the native enantiomer as well.

Analysis of Tryptophan and Its Metabolites by High-Performance Liquid Chromatography

Tryptophan is a nutritionally essential amino acid for both humans and animals. Besides acting as a building block for protein synthesis, tryptophan (Trp) and its metabolites are crucial for maintaining neurological function, immunity, and homeostasis in the body. To uncover the regulatory role of Trp and its metabolites in cell nutrition, metabolism and physiology, various analytical methods, including high-performance liquid chromatography (HPLC), have been developed to determine key Trp metabolites. Here we describe a rapid and sensitive method for the simultaneous analysis of Trp and its metabolites along with other amino acids by HPLC involving in-line pre-column derivatization with o-phthaldialdehyde (OPA) and dual-channel fluorescence detection. OPA reacts very rapidly (within 1 min) with Trp, 5-hydroxytryptophan, 5-hydroxytryptamine, and tryptamine at room temperature (e.g., 20-25 °C) in an autosampler. Their derivatives are immediately injected into the HPLC column without the need for extraction. Trp metabolites that cannot react with OPA but are fluorescent can be detected by setting the excitation and emission wavelengths of the fluorescence detector in another detection channel. The autosampler is programmed to mix Trp and its metabolites with OPA for 1 min to generate highly fluorescent derivatives for HPLC separation and detection (Channel A, excitation = 270 nm and emission = 350 nm; Channel B, excitation = 340 nm and emission = 450 nm). The detection limit for Trp and its metabolites is 30 pmol/mL or 150 fmol/injection. The total time for chromatographic separation (including column regeneration) is 55 min for each sample. Our HPLC method can be used for the analysis of amino acids (including Trp) in alkaline protein hydrolysates and of Trp and its metabolites in biological samples.

Untargeted Soil Metabolomics Using Liquid Chromatography-Mass Spectrometry and Gas Chromatography-Mass Spectrometry

The molecular composition of soil organic matter (SOM) sets the foundation for terrestrial microbial community structures and carbon cycling dynamics. However, the specific chemical constituents of SOM are underexplored. In this chapter we present a protocol for the extraction of small molecule metabolites from soil followed by compound detection and identification using liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry. There are options within the protocol to assess either the extracellular pool of metabolites or the total pool (including intracellular) and either polar or nonpolar metabolites, depending on the reader's research interests. These methods can be followed individually for a more targeted analysis or all methods can be combined to obtain a more comprehensive understanding of SOM metabolite composition (such as amino acids, nucleobases, organic acids, fatty acids, carbohydrates, secondary metabolites, and antibiotics).

Direct Analysis of Underivatized Amino Acids in Plant Extracts by LC-MS/MS (Improved Method)

In this chapter we describe a method for quantification of 20 proteinogenic amino acids by liquid chromatography-mass spectrometry which affords neither derivatization nor the use of organic solvents. Analysis of the underivatized amino acids is performed by liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) in the positive ESI mode. Separation is achieved on a strong cation exchange (SCX) column (Luna 5 μ SCX 100 Å) with 5% acetic acid in water (A) and 75 mM ammonium acetate in water (B). Quantification is accomplished by use of d₂-phenylalanine as internal standard achieving limits of detection of 5-50 nM. The method was successfully applied for the determination of proteinogenic amino acids in plant extracts.

A High-Throughput Targeted Metabolomics Workflow for the Detection of 200 Polar Metabolites in Central Carbon Metabolism

Targeted metabolomics aims to analyze a set of pre-selected metabolites from biologically relevant metabolic pathways. The triple quadrupole mass spectrometry (QqQ-MS) based multiple reaction monitoring (MRM) technique is the most widely approach used for targeted metabolomics, and features high selectivity and sensitivity, good reproducibility and wide dynamic range in quantitative analysis. Here, we describe an MRM based targeted metabolomics workflow for the quantitative analysis of 200 polar metabolites in central carbon metabolic pathways, including the data acquisition method and the automated data processing procedures using our in-house R package MRMAnalyzer. The workflow described in this chapter combines a hydrophilic interaction liquid chromatography (HILIC) separation and positive/negative ion polarity switching based MS detection, and is able to acquire data from multiple types of biological samples such as bacteria, cultured mammalian cells, animal tissues and biofluids (e.g., serum and urine). Finally, the MRMAnalyzer software can automatically process the generated large-scale data set with high efficiency. We hope it is a valuable and efficient workflow for researchers to facilitate the respective biological studies using targeted metabolomics.

A Protocol to Compare Methods for Untargeted Metabolomics

There are thousands of published methods for profiling metabolites with liquid chromatography/mass spectrometry (LC/MS). While many have been evaluated and optimized for a small number of select metabolites, very few have been assessed on the basis of global metabolite coverage. Thus, when performing untargeted metabolomics, researchers often question which combination of extraction techniques, chromatographic separations, and mass spectrometers is best for global profiling. Method comparisons are complicated because thousands of LC/MS signals (so-called features) in a typical untargeted metabolomic experiment cannot be readily identified with current resources. It is therefore challenging to distinguish methods that increase signal number due to improved metabolite coverage from methods that increase signal number due to contamination and artifacts. Here, we present the credentialing protocol to remove the latter from untargeted metabolomic datasets without having to identify metabolite structures. This protocol can be used to compare or optimize methods pertaining to any step of the untargeted metabolomic workflow (e.g., extraction, chromatography, mass spectrometer, informatic software, etc.).

Chemical Stability of Progesterone in Compounded Oral Rapid-dissolving Tablets

Progesterone is a naturally occurring female sex hormone, which plays an important role in the female reproductive cycle. Progesterone supplementation is used to treat a variety of conditions. When commercial dosage strengths are unavailable, rapid-dissolving tablets may be compounded. The objective of this study was to evaluate the chemical stability of progesterone when compounded in a rapid-dissolving tablet formulation and to establish an evidence-based beyond-use date. Triplicate test samples were prepared by diluting the pulverized progesterone rapid-dissolving tablets with a portion of methanol to a final concentration of 100 µg/mL. Samples were stored in a stability chamber under accelerated conditions at 60°C and 75% relative humidity and were evaluated at appropriate intervals (0, 6 months, and 12 months). Chemical stability was assessed initially and at appropriate intervals during the study periods with stability-indicating high-performance liquid chromatography analytical techniques based on the determination of drug concentrations. The results of high-performance liquid chromatography analysis indicated that the samples remained stable for 6 months at 60°C and 75% relative humidity. The remaining concentration of progesterone rapid-dissolving tablets at 6 months fell within the United States Pharmacopeia accepted limits (±10% of the initial concentration), which was consistent with the recommended beyond-use dating of 6 months for a non-aqueous formulation per United States Pharmacopeia guidelines.

Amino Acid Analysis in Physiological Samples by GC-MS with Propyl Chloroformate Derivatization and iTRAQ-LC-MS/MS

Two mass spectrometry-based methods for the quantitative analysis of free amino acids are described. The first method uses propyl chloroformate/propanol derivatization and gas chromatography-quadrupole mass spectrometry (GC-qMS) analysis in a single-ion monitoring mode. Derivatization is carried out directly in the aqueous samples, thereby allowing automation of the entire procedure, including addition of reagents, extraction, and injection into the GC-MS. The method delivers the quantification of 26 amino acids. The iTRAQ method employs the labeling of amino acids with isobaric iTRAQ tags. The tags contain two different cleavable reporter ions, one for the sample and one for the standard, which are detected by fragmentation in a tandem mass spectrometer (MS/MS). Reversed-phase liquid chromatography (RP-LC) of the labeled amino acids is performed prior to mass spectrometric analysis to separate isobaric amino acids. The commercial iTRAQ kit allows for the analysis of 42 physiological amino acids with a respective isotope-labeled standard for each of these 42 amino acids.

Methods for Absolute Quantification of Human Plasma Free Amino Acids by High-Performance Liquid Chromatography/Electrospray Ionization Mass Spectrometry Using Precolumn Derivatization

Plasma free amino acid (PFAA) concentrations in humans are affected by various diseases. However, the variations caused are not dramatic, so a high accurate and precise method for analyzing PFAAs is required. The PFAA analysis protocol described in this chapter covers blood sampling, sample pretreatment, amino acid derivatization, and LC-MS analysis. Each procedure is important for accurate and precise quantification.In the protocol, a human blood sample is collected using an EDTA-2Na or 2K vacuum collection tube and then immediately cooled in water mixed with crushed ice. The sample is then centrifuged on cooling to allow a plasma sample to be removed. A stable-isotope-labeled internal standard solution is added to the plasma, and then the plasma is deproteinized with acetonitrile. The amino acids in the plasma are then derivatized using 3-aminopyridyl-N-hydroxysuccinimidyl carbamate (APDS) reagent which is designed for LC-MS analysis. The derivatized amino acids are separated by reverse-phase HPLC and detected by electrospray ionization mass spectrometry. Using this method, 21 amino acids in human plasma can be analyzed with a 12 min cycle. The accuracy and precision are both better than the required criteria given by the US Food and Drug Administration in guidance of Bioanalytical Method Validation.

UPLC⁻MS/MS Identification of Sterol Sulfates in Marine Diatoms

Diatoms are unicellular eukaryotic organisms that play a key ecological and biogeochemical role in oceans as major primary producers. Recently, these microalgae have also attracted interest as a promising source of functional products with widespread relevance. Progress in the knowledge of cell and molecular biology of diatoms is envisaged as a key step to understanding regulation of their life cycle in marine environments as well as facilitating their full and profitable exploitation by biotechnological platforms. Recently, we identified sterol sulfates (StS) as regulatory molecules of cell death in the diatom Skeletonema marinoi. As these compounds may have a general role in diatom physiology and chemical signals in aquatic systems, we investigated a suitable tool for their analysis in laboratory and field samples. Herein, we describe a sensitive, fast, and efficient ultra performance liquid chromatography–mass spectrometry (UPLC–MS) method for qualitative and quantitative analysis of StS from crude extract of diatoms and other microalgae. The method was applied to 13 different strains of our collection of marine protists. This first study suggested a species-specific distribution of StS and identified the sulfated derivatives of 24-methylene cholesterol and 24-methyl cholesterol as the most common members in diatoms.

MS/MS-Based Molecular Networking Approach for the Detection of Aplysiatoxin-Related Compounds in Environmental Marine Cyanobacteria

Certain strains of cyanobacteria produce a wide array of cyanotoxins, such as microcystins, lyngbyatoxins and aplysiatoxins, that are associated with public health issues. In this pilot study, an approach combining LC-MS/MS and molecular networking was employed as a rapid analytical method to detect aplysiatoxins present in four environmental marine cyanobacterial samples collected from intertidal areas in Singapore. Based on 16S-ITS rRNA gene sequences, these filamentous cyanobacterial samples collected from Pulau Hantu were determined as Trichodesmium erythraeum, Oscillatoria sp. PAB-2 and Okeania sp. PNG05-4. Organic extracts were prepared and analyzed on LC-HRMS/MS and Global Natural Product Social Molecular Networking (GNPS) for the presence of aplysiatoxin-related molecules. From the molecular networking, six known compounds, debromoaplysiatoxin (1), anhydrodebromoaplysiatoxin (2), 3-methoxydebromoaplysiatoxin (3), aplysiatoxin (4), oscillatoxin A (5) and 31-noroscillatoxin B (6), as well as potential new analogues, were detected in these samples. In addition, differences and similarities in molecular networking clusters related to the aplysiatoxin molecular family were observed in extracts of Trichodesmium erythraeum collected from two different locations and from different cyanobacterial species found at Pulau Hantu, respectively.

Seasonal Variations in the Metabolome and Bioactivity Profile of Fucus vesiculosus Extracted by an Optimised, Pressurised Liquid Extraction Protocol

The metabolism of seaweeds depends on environmental parameters, the availability of nutrients, and biotic/abiotic stresses; therefore, their chemical composition fluctuates throughout the year. This study investigated seasonal variations in the metabolome of the Baltic Sea brown alga Fucus vesiculosus and its potential relation to the bioactivity profile. By using a definitive screening design (DSD) combined with pressurised liquid extraction (PLE), an optimised protocol was developed to extract algal biomass monthly for a full calendar year. An untargeted metabolomics approach using ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MSn)-based molecular networking and manual dereplication was employed. The extracts were simultaneously screened for their in vitro antimicrobial, anticancer/apoptotic, and free radical scavenging activities. 44 compounds were putatively dereplicated in the metabolome. Many compounds were found to vary with the sampling month; phlorotannin total ion count (TIC) was highest in summer, whilst chlorophylls, lipids, and carotenoids peaked in winter and spring. The greatest radical scavenging and apoptotic activities against pancreas cancer cells observed in the summer months were attributed to high phlorotannin TIC. Methicillin-resistant Staphylococcus aureus (MRSA) inhibitory activity was produced year-round without a clear seasonal trend. This is the first study applying DSD-based optimised PLE extraction combined with a metabolome analysis of F. vesiculosus for the identification of seasonal variations in both metabolome and bioactivity.

High-throughput metabolomics investigates anti-osteoporosis activity of oleanolic acid via regulating metabolic networks using ultra-performance liquid chromatography coupled with mass spectrometry

BACKGROUND

Osteoporosis has brought about heavy socio-economic burden in the morbidity and medical expenses associated with osteoporosis treatment and various restrictions on behavior of their social roles. Oleanolic acid (OA) is an anti-osteoporosis natural product, but molecular mechanisms of therapeutic effect are not still well known.

PURPOSE

In this study, we explore anti-osteoporosis activity of oleanolic acid and predict the underlying mechanisms by metabolomics strategy.

METHODS

SD rats were intraperitoneal injection with prednison for once to establish osteoporosis model. Using metabolomics strategy based on ultra-performance liquid chromatography coupled with quadrupole time-of-flight/ mass spectrometry (UPLC-TOF/MS), serum samples of 24 rats were analyzed to seek differential metabolites and pathway associated with OA treatment of osteoporosis. In addition, the effect of OA on osteoporosis rats was also evaluated by clinical biochemistry indicators and bone density analysis.

RESULTS

Clinical biochemistry indicators and bone density of lumbar and femur were reversed by OA treatment. A total of 25 potential biomarkers were identified in the rats model of glucocorticoid-induced osteoporosis, and oleanolic acid have a regulatory effect on 17 of them that related to some vital metabolic pathway such as linoleic acid metabolism, valine, leucine and isoleucine biosynthesis, phenylalanine, tyrosine and tryptophan biosynthesis as well as cysteine and methionine metabolism. The ingenuity pathway analysis (IPA) platform is applied to further understanding the relationship between metabolic changes and therapeutic effect of OA, which the disordered state carbohydrate metabolism, molecular transport and lipid metabolism in glucocorticoid-induced osteoporosis rats are mainly ameliorated by oleanolic acid.

CONCLUSION

Metabolomics provides a novel method to investigate the anti-osteoporosis effects of OA and probe into the potential mechanisms, and will contributes to the development of new drugs.

Rapid detection of resistance to carbapenems and cephalosporins in Enterobacteriaceae using liquid chromatography tandem mass spectrometry

Carbapenemase producing Enterobacteriaceae (CPE) are becoming a global healthcare concern. Current laboratory methods for the detection of CPE include screening followed by confirmatory phenotypic and genotypic tests. These processes would generally take ≥72 hours, which could negatively impact patient care and Infection Control practices. To this end, we developed a protocol for rapid resistance testing (RRT) to detect hydrolysis in a panel of beta lactam antibiotics consisting of ampicillin, cefazolin, cefotaxime and imipenem, using liquid chromatography tandem mass spectrometry. Ninety—nine beta lactamase producing Enterobacteriaceae isolates were used to evaluate the RRT method, 54 isolates were CPE and 45 isolates were Class A or AmpC beta lactamase producing Enterobacteriaceae but not carbapenemase producers. We also tested 10 E.coli isolates that were susceptible to ampicillin, cefazolin, cefotaxime and imipenem. Receiver Operating Characteristic (ROC) Curves analysis showed that imipenem had a sensitivity and a specificity of 100% for crabapenemase detection at hydrolysis cut off values that are greater than 50% and less than or equal to 80%. The RRT protocol can be conducted in a time frame of less than 2 hours. This preliminary study shows that the rapid resistance testing protocol might have utility for the rapid detection of CPE. Additional work with a greater number and variety of beta- lactamase producing Enterobacteriaceae isolates is required to validate these preliminary findings.

Rapid monitoring of plant growth regulators in bean sprouts via automated on-line polymeric monolith solid-phase extraction coupled with liquid chromatography tandem mass spectrometry

An automated on-line solid-phase extraction (SPE) following liquid chromatography tandem mass spectrometry was established for the fast determination of plant growth regulator residues in soybean sprout and mung bean sprout. The crude extracted specimens were directly purified on a poly (2-(dimethylamino) ethyl methacrylate-co-ethylene dimethacrylate) monolithic column which was well-defined as the on-line SPE adsorbent. Under the optimized conditions, the developed method gave the linear range of 0.3-50 ng/mL for gibberellin and 2,4-dichlorophenoxyacetic acid, 0.2-50 ng/mL for 4-chlorophenoxyacetic acid, and 0.5-50 ng/mL for 1-naphthaleneacetic acid (r ≥ 0.998). The detection limits (S/N = 3) ranged from 1.0 to 2.5 μg/kg and the recoveries for spiked soybean sprout samples were in the range of 75.0-93.3%. Besides, the total time for one analysis was 16 min. The reusability of the monolith was up to 600 extractions. The proposed process facilitated fully automated SPE and accurate determination in one step with rapidity, simplicity, and reliability. Graphical abstract ᅟ.

Determination of kaurenoic acid in rat plasma using UPLC-MS/MS and its application to a pharmacokinetic study

Kaurenoic acid (KA), a kaurane diterpene found in several medicinal plants, is an active ingredient with potential anti-inflammatory, anticonvulsant, antibacterial and antitumor activities. In this work, an ultra-performance liquid chromatography-tandem mass spectrometry method (UPLC-MS/MS) was firstly developed and validated to quantify kaurenoic acid in rat plasma. Rhein was chosen as the internal standard (IS) and the plasma was processed with one-step acetonitrile protein precipitation; the chromatographic separation was achieved on a HSS T3 (2.1 × 50 mm, 1.8 μm) column with the mobile phase consisting of acetonitrile and water containing 0.1% formic acid via gradient elution. An electrospray ionization source was applied and operated in the negative ion and multiple reaction monitoring (MRM) modes. Kaurenoic acid and IS were quantified using the transitions of m/z 301.2→301.2 (pseudo MRM) and m/z 283.2 → 238.9, respectively. The calibration curves were linear over the range of 5∼ 100 ng/mL (R² = 0.990). The lower limit of quantification (LLOQ) was 5 ng/mL. The intra- and inter- day precision (RSD) ranged from 3.0% to 11.4%. The matrix effect and extraction recovery were within acceptable limits. The validated method was successfully applied to the pharmacokinetic study of kaurenoic acid in rats after oral administration at three dosages.

Aptasensors as the future of antibiotics test kits-a case study of the aptamer application in the chloramphenicol detection

Antibiotics are a type of antimicrobial drug with the ubiquitous presence in foodstuff that effectively applied to treat the diseases and promote the animal growth worldwide. Chloramphenicol as one of the antibiotics with the broad action spectrum against Gram-positive and Gram-negative bacteria is widely applied for the effective treatment of infectious diseases in humans and animals. Unfortunately, the serious side effects of chloramphenicol, such as aplastic anemia, kidney damage, nausea, and diarrhea restrict its application in foodstuff and biomedical fields. Development of the sufficiently sensitive methods to detect chloramphenicol residues in food and clinical diagnosis seems to be an essential demand. Biosensors have been introduced as the promising tools to overcome the requirement. As one of the newest types of the biosensors, aptamer-based biosensors (aptasensors) are the efficient sensing platforms for the chloramphenicol monitoring. In the present review, we summarize the recent achievements of the accessible aptasensors for qualitative detection and quantitative determination of chloramphenicol as a candidate of the antibiotics. The present chloramphenicol aptasensors can be classified in two main optical and electrochemical categories. Also, the other formats of the aptasensing assays like the high performance liquid chromatography (HPLC) and microchip electrophoresis (MCE) have been reviewed. The enormous interest in utilizing the diverse nanomaterials is also highlighted in the fabrication of the chloramphenicol aptasensors. Finally, some results are presented based on the advantages and disadvantages of the studied aptasensors to achieve a promising perspective for designing the novel antibiotics test kits.

Boronate Affinity Chromatography Accurately Measures HbA1c also in Patients with End-Stage Renal Disease - Performance Evaluation of the A1c HPLC Analyzer

BACKGROUND

Boronate affinity chromatography is widely used, and the method has lately been improved and designed for HbA1c measurements. We report performance evaluation of the affinity chromatography HbA1c HPLC analyzer.

METHODS

Within- and between-run imprecision was assessed based on the results of a series of measurements in three different EDTA blood samples and in control materials. HbA1c levels were measured and compared in 349 EDTA blood samples and 50 samples from patients with end-stage renal disease (ESRD) using the Premier Hb9210 analyzer (affinity chromatography) and the D-10 Hemoglobin Testing System (ion-exchange chromatography).

RESULTS

The within- and between-run imprecision CVs ranged from 0.72% to 2.01%. Median HbA1c level measured by the Premier Hb9210 was significantly lower (6.4% [46 mmol/mol] vs. 6.6% [49 mmol/mol], p < 0.001). The Passing-Bablok agreement test yielded a slope of 1.0 (95% CI: 1.0 to 1.0) and intercept of -0.1 (95% CI: -0.1 to -0.1). Correlation coefficient and the mean difference amounted to 0.992 and -0.13% (95% CI: -0.11 to -0.15), respectively. Similar results were obtained for HbA1c levels < 7% [< 53 mmol/mol] and ≥ 7% [≥ 53 mmol/mol]. In ESRD patients, median HbA1c level measured by the Premier Hb9210 was also significantly lower (6.0% [42 mmol/mol] vs. 6.5 [48 mmol/mol], p < 0.001) with the mean difference equal to -0.52% (95% CI: -0.59 to -0.46).

CONCLUSIONS

Although the Premier Hb9210 gave lower HbA1c levels, good results agreement with the D-10 Hemoglobin Testing System was found. Analytical performance found for HbA1c measurements in ESRD patients was similar. The Premier Hb9210 analyzer is suitable for routine HbA1c testing in clinical practice.

Position-specific 13 C/12 C analysis of amino acid carboxyl groups - automated flow-injection analysis based on reaction with ninhydrin

RATIONALE

The fundamental level of stable isotopic knowledge lies at specific atomic positions within molecules but existing methods of analysis require lengthy off-line preparation to reveal this information. An automated position-specific isotope analysis (PSIA) method is presented to determine the stable carbon isotopic compositions of the carboxyl groups of amino acids (δ¹³ C_CARBOXYL values). This automation makes PSIA measurements easier and routine.

METHODS

An existing high-performance liquid chromatography (HPLC) gas handling interface/stable isotope ratio mass spectrometry system was modified by the addition of a post-column derivatisation unit between the HPLC system and the interface. The post-column reaction was optimised to yield CO₂ from the carboxyl groups of amino acids by reaction with ninhydrin.

RESULTS

The methodology described produced δ¹³ C_CARBOXYL values with typical standard deviations below ±0.1 ‰ and consistent differences (Δ¹³ C_CARBOXYL values) between amino acids over a 1-year period. First estimates are presented for the δ¹³ C_CARBOXYL values of a number of internationally available amino acid reference materials.

CONCLUSIONS

The PSIA methodology described provides a further dimension to the stable isotopic characterisation of amino acids at a more detailed level than the bulk or averaged whole-molecule level. When combined with on-line chromatographic separation or off-line fraction collection of protein hydrolysates the technique will offer an automated and routine way to study position-specific carboxyl carbon isotope information for amino acids, enabling more refined isotopic studies of carbon uptake and metabolism.

Assembly of PGAM5 into Multimeric Complexes Provides a Mechanism for Allosteric Regulation of Phosphatase Activity

Phosphoglycerate mutase family member 5 (PGAM5) is a serine/threonine phosphatase that has been localized to both inner and outer mitochondrial membranes. PGAM5 has been suggested to regulate multiple aspects of mitochondrial dynamics, including fission/fusion and mitophagy, through phosphatase-dependent and phosphatase-independent mechanisms. Understanding how the phosphatase activity of PGAM5 is regulated will provide new insight into signaling mechanisms that link changes in cell physiology with mitochondrial function. In this chapter, we describe methods for obtaining both multimeric and dimeric complexes of PGAM5 and for characterizing their kinetic properties. The ability to purify different PGAM5 complexes and to characterize their kinetic properties will enable detailed biophysical studies of the quaternary structures of the various PGAM5-containing complexes. The phosphatase activity of different PGAM5 complexes varies over three orders of magnitude. We suggest that the ability to generate PGAM5 complexes that have a wide range of phosphatase activities will facilitate screens to identify small molecules that modulate the phosphatase activity of PGAM5.

Validated LC-MS/MS method for the determination of amlodipine enantiomers in rat plasma and its application to a stereoselective pharmacokinetic study

A rapid and sensitive method was established to determine amlodipine enantiomers using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Stereoselective separation was performed on CHIRALCEL OZ-RH column (150 mm × 4.6 mm i.d., 5 μm) with acetonitrile-water (10 mM ammonium acetate, 0.5% ammonia solution) (95:5, v/v) at a flow rate of 0.5 mL/min. The substances were detected by mass spectrometer equipped with an electrospray ionization source interface in positive ion mode. Multiple reaction monitoring was selected with the transition of the m/z 409.1 → 238.0 for amlodipine enantiomers and m/z 237.0 → 194.1 for carbamazepine (IS) respectively. Calibration curves were linear at the range of 0.9375-120 ng/mL for both isomers with r > 0.99, while using a lower sample volume (50 μL) compared with previously reported enantiospecific methods The accuracy was at the range of 84.1-119.0% for R-amlodipine, and 87.4-118.2% for S-amlodipine, respectively. The within- and between-run precision (CV%) was within 10% in all cases for both enantiomers. Enantiomers were stable under different conditions, e.g. processed sample, short-term, residue, long-term and freeze/thaw. The LC-MS/MS method was successfully applied in pharmacokinetic study of amlodipine enantiomers in rats. It was observed the concentration of the S- amlodipine was significantly higher than that of the R-amlodipine in racemate-treated group. And there was no significant difference in the pharmacokinetic profiles of the S-amlodipine between the 10 mg/kg racemate- and 5 mg/kg S-amlodipine-treated groups. In addition, it was the first time to find that the main pharmacokinetic parameters (AUC_(0-t), AUC_(0-∞) and C_max) of R-amlodipine were significantly lower in the 5 mg/kg R-amlodipine-treated group compared with the racemate-treated group.

Simultaneous determination of tryptophan, kynurenine, kynurenic acid and two monoamines in rat plasma by HPLC-ECD/DAD

A high-performance liquid chromatography method with a diode array and an electrochemical detection (HPLC-ECD/DAD) was developed to determine the levels of tryptophan (TRP), kynurenine (KYN), kynurenic acid (KYA), 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) in rat plasma. The prepared samples were separated on a BDS column (4.6 mm × 250 mm, 5 mm) with column oven temperature of 25 °C. The mobile phase consisted of 5% acetonitrile and a buffer solution, which contained 25 mmol/L sodium acetate and 0.01 mmol/L EDTA, adjusting pH to 4.5 with acetic acid, and it was pumped at a flow-rate of 1.0 mL/min. KYN and KYA were measured by a variable wavelength detector at wavelengths 360 nm and 333 nm respectively, TRP and vanillic acid (as IS) both were measured at 280 nm. Determination of 5-HT and 5-HIAA was accomplished at the electrochemical working potential of 700 mV. Total run time was 14 min. Several parameters of the developed method were validated including linearity, accuracy precision, and stability. The results showed the established method had good LOD and separation for all of the five compounds and IS in the biological matrix. The method is simple, fast, economical and accurate. The analytical method and the results could provide a reference for the clinical and scientific research of depression.

A novel and effective mode-switching triple quadrupole mass spectrometric approach for simultaneous quantification of fifteen ginsenosides in Panax ginseng

BACKGROUND

Panax ginseng (PG) is one of the most valuable and frequently used phytomedicine in Asia. In the current Chinese Pharmacopeia, only three ginsenosides, Rg1, Re and Rb1, were set as standard compounds for the quality evaluation of PG. However, only these three compounds could hardly reflect the quality and therapeutic efficacy of this traditional Chinese medicine (TCM).

PURPOSE

Quantification analysis of quality markers (Q-markers) in PG is meaningful for determining the quality of this herbal medicine.

METHOD

By combining the modes of multiple reaction monitoring (MRM) and single ion monitoring (SIM) of tripe quadrupole mass spectrometry (QqQ-MS) through a mode-switching function, a novel, sensitive and effective LC-MS/MS method has been established to simultaneous quantify fifteen Q-markers in PG in one run time cycle. In order to comprehensively evaluate the quality of ten batches of PG, hierarchical clustering analysis (HCA) and the complete linkage method were conducted on the data of the contents of fifteen ginsenosides.

RESULTS

Thirteen Q-markers, including four pairs of isomers with the same product ions and approximately the same retention times, have been well-separated by MRM. Meanwhile, the other two Q-markers with no fragments have also been quantified by SIM. Chromatographic separation was carried out on a reversed-phase C₁₈ column by stepwise gradient elution with a mobile phase of water (containing 0.1% formic acid, v/v) and acetonitrile. Good linearity was observed with the correlation coefficients (r²) greater than 0.99. The intra- and inter-day precisions as well as repeatability of all of the investigated Q-markers were all no more than 5.91%. The average recoveries varied from 83.06% to 116.42%, with relative standard deviation values (RSDs) less than 6.73%. The total contents of the fifteen ginsenosides in ten batches of PG were in the range of 15.54-24.03 mg/g. The results indicated that the growing region has a significant impact on the contents of ginsenosides in PG.

CONCLUSION

The proposed approach could be readily utilized as a comprehensive approach for determining the consistency of the quality and therapeutic efficacy of PG, and it might be an example for the selection of Q-marker standards for the Chinese Pharmacopoeia.

Characterization by liquid chromatography-mass spectrometry and antioxidant activity of an ethanolic extract of Inula viscosa leaves

Inula viscosa (I. viscosa) is a common Mediterranean plant, well known for its content on bioactive molecules. The chemical composition of an ethanolic extract from I. viscosa leaves, growing in Algeria, was analysed by liquid chromatography coupled to photodiode array detection and electrospray ionization mass spectrometry (LC-DAD-ESI-MS/MS) operating in negative and positive mode. The methodology used revealed the presence of 51 compounds from which 47 were putatively identified, including 11 phenolic acids, 23flavonoids, one lignan and 12 terpenoids. Twenty-six of these compounds are described for the first time in I. viscosa. Antioxidant activity was measured using three different and complementary chemical assays: DPPH radical scavenging activity, oxygen radical absorbance capacity (ORAC) and hydroxyl radical scavenging capacity (HOSC). Results demonstrate that ethanolic leaf extract exhibit a high scavenging ability against DPPH (157.72 ± 6.45 μM TE/g DW), peroxyl (4471.42 ± 113.16 μM TE/g DW) and hydroxyl (630.10 ± 17.81 μM TE/g DW) radicals, indicating that I. viscosa can be a promising source of bioactive compounds.

Vitamin B12 (cyanocobalamin) in Infant Formula Adult/Pediatric Nutritional Formula by Liquid Chromatography with Ultraviolet Detection: Collaborative Study, Final Action 2014.02

To determine the repeatability and reproducibility figures of the AOAC First Action Official MethodSM 2014.02 (Vitamin B12 in Infant Formula and Adult/Pediatric Formula by Liquid Chromatography with UV Detection), a collaborative study was organized. Twenty-one laboratories located in 13 different countries agreed to participate. The study was divided into two parts. During the first part, the laboratories analyzed two samples in duplicate by using the method described in the protocol. The laboratories that provided results within the expected range were qualified for part two, during which they analyzed 10 samples in blind duplicates. Eighteen laboratories managed to provide results on time for reporting. The results were compared with the Standard Method Performance Requirement (SMPR® 2011.005) established for vitamin B12. The precision results met the requirements stated in the SMPR except for one sample. Repeatability and reproducibility relative standard deviation ranged from 1.1 to 6.5% and from 6.0 to 23.8%, respectively, with only one matrix showing reproducibility values higher than the required 11%. Horwitz ratio values were all well below 2 (0.17-0.78). The AOAC Expert Review Panel (Stakeholder Panel for Infant Formula and Adult Nutritional Expert Review Panel) determined that the data presented met the SMPR and, hence, recommended the method to be granted Final Action status in September 2016.

Novel bio analytical method development, validation and application for simultaneous determination of nebivolol and S-amlodipine in human plasma using ultra performance liquid chromatography-tandem mass spectrometry

A sensitive and specific ultra-performance liquid chromatography tandem mass spectrometric (UPLC-MS/MS) method has been developed, validated and applied for the assay of Nebivolol and S-amlodipine in human plasma. Sample extraction was carried out through hybrid extraction method from 250 μL of human plasma sample. Linearity of the method was (r ≥ 0.9996) was found to be dynamic for both the analytes over concentration range of 25.0-4000 pg/mL. Chromatographic separation was achieved on UPLC column {Waters Acquity UPLC BEH C18 (50 mm × 2.1 mm, 1.7 micrometer)} with the mobile phase composition of 0.1% (v/v) formic acid in 5 mM Ammonium formate in water-acetonitrile (20:80, %v/v). Analytes Stability was assured under different requisite conditions in human plasma, reconstitution solution and diluents. Inter and intra-day assay precision and relative error (accuracy) were within ±5% for both analytes. The method was applied and reproduced to support a pharmacokinetic study of 5 mg Nebivolol (NEB) and 2.5 mg S-amlodipine (LAM) tablet on 9 healthy subjects.

Development and validation of an assay to analyze atazanavir in human hair via liquid chromatography/tandem mass spectrometry

RATIONALE

Assays to quantify antiretrovirals in hair samples are increasingly used to monitor adherence and exposure in both HIV prevention and treatment studies. Atazanavir (ATV) is a protease inhibitor used in combination antiretroviral therapy (ART). We developed and validated a liquid chromatography/tandem mass spectrometry (LC/MS/MS)-based method to quantify ATV in human hair, per the NIH Division of AIDS Clinical Pharmacology Quality Assurance (CPQA) program and the FDA bioanalytical method validation guidelines.

METHODS

ATV was extracted from hair using optimized methods and the extracts were injected onto a BDS C-18 column (5 μm, 4.6 × 100 mm), followed by isocratic elution via a mobile phase composed of 55% acetonitrile, 45% water, 0.15% acetic acid, and 4 mM ammonium acetate, at a flow rate of 0.8 mL/min prior to analysis by MS/MS. Levels were quantified using positive electrospray ionization by multiple reaction monitoring (MRM) for the transitions MH⁺ m/z 705.3 to m/z 168.0 and MH⁺ m/z 710.2 to m/z 168.0 for ATV and ATV-d5 (internal standard), respectively.

RESULTS

Our assay demonstrated a linear standard curve (r = 0.99) over the concentration range of 0.0500 ng ATV/mg hair to 20.0 ng/mg hair. The inter- and intraday accuracy of ATV quality control (QC) samples was -1.33 to 4.00% and precision (% coefficient of variation (%CV)) was 1.75 to 6.31%. The %CV for ATV levels in hair samples from highly adherent patients (incurred samples) was less than 10%. No significant endogenous peaks or crosstalk were observed in the specificity test with other HIV drugs. The overall extraction efficiency of ATV from incurred hair samples was greater than 95%.

CONCLUSIONS

This highly sensitive, highly specific and validated assay can be considered for therapeutic drug monitoring for HIV-infected patients on ATV-based ART.

Chemiluminescent Determination of Oxamyl in Drinking Water and Tomato Using Online Postcolumn UV Irradiation in a Chromatographic System

High-performance liquid chromatography (HPLC) was used to separate oxamyl from other pesticides in drinking water and tomato paste. The eluate emerging from the column tail was mixed with an alkaline solution of Co²⁺ in EDTA and irradiated with UV light to induce photolysis of the carbamate in order to obtain free radicals and other reactive species that oxidize luminol and produce chemiluminescence (CL) as a result. The intensity of the CL signal was monitored in the form of chromatographic peaks. Under the optimum operating conditions for the HPLC-UV-CL system, the analyte concentration was linearly related to peak area. The limit of detection as determined in accordance with the IUPAC criterion was 0.17 mg L^-1. Oxamyl was successfully extracted with recoveries of 88.7-103.1% from spiked tomato paste by using a simple QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) sample preparation approach. Similar recoveries were obtained from drinking water samples spiked with oxamyl concentrations above the LOD. The proposed method is a simple, fast, accurate choice for quantifying this pesticide.

Automated Online Solid-Phase Derivatization for Sensitive Quantification of Endogenous S-Nitrosoglutathione and Rapid Capture of Other Low-Molecular-Mass S-Nitrosothiols

S-Nitrosothiols (RSNOs) constitute a circulating endogenous reservoir of nitric oxide and have important biological activities. In this study, an online coupling of solid-phase derivatization (SPD) with liquid chromatography-mass spectrometry (LC-MS) was developed and applied in the analysis of low-molecular-mass RSNOs. A derivatizing-reagent-modified polymer monolithic column was prepared and adapted for online SPD-LC-MS. Analytes from the LC autosampler flowed through the monolithic column for derivatization and then directly into the LC-MS for analysis. This integration of the online derivatization, LC separation, and MS detection facilitated system automation, allowing rapid, laborsaving, and sensitive detection of RSNOs. S-Nitrosoglutathione (GSNO) was quantified using this automated online method with good linearity (R2 = 0.9994); the limit of detection was 0.015 nM. The online SPD-LC-MS method has been used to determine GSNO levels in mouse samples, 138 ± 13.2 nM of endogenous GSNO was detected in mouse plasma. Besides, the GSNO concentrations in liver (64.8 ± 11.3 pmol/mg protein), kidney (47.2 ± 6.1 pmol/mg protein), heart (8.9 ± 1.8 pmol/mg protein), muscle (1.9 ± 0.3 pmol/mg protein), hippocampus (5.3 ± 0.9 pmol/mg protein), striatum (6.7 ± 0.6 pmol/mg protein), cerebellum (31.4 ± 6.5 pmol/mg protein), and cortex (47.9 ± 4.6 pmol/mg protein) were also successfully quantified. When the derivatization was performed within 8 min, followed by LC-MS detection, samples could be rapidly analyzed compared with the offline manual method. Other low-molecular-mass RSNOs, such as S-nitrosocysteine and S-nitrosocysteinylglycine, were captured by rapid precursor-ion scanning, showing that the proposed method is a potentially powerful tool for capture, identification, and quantification of RSNOs in biological samples.

Capillary-based integrated digital PCR in picoliter droplets

The droplet digital polymerase chain reaction (ddPCR) is becoming more and more popular in diagnostic applications in academia and industry. In commercially available ddPCR systems, after they have been made by a generator, the droplets have to be transferred manually to modules for amplification and detection. In practice, some of the droplets (∼10%) are lost during manual transfer, leading to underestimation of the targets. In addition, the droplets are also at risk of cross-contamination during transfer. By contrast, in labs, some chip-based ddPCRs have been demonstrated where droplets always run in channels. However, the droplets easily coalesce to large ones in chips due to wall wetting as well as thermal oscillation. The loss of droplets becomes serious when such ddPCRs are applied to absolutely quantify rare mutations, such as in early diagnostics in clinical research or when measuring biological diversity at the cell level. Here, we propose a capillary-based integrated ddPCR system that is used for the first time to realize absolute quantification in this way. In this system, a HPLC T-junction is used to generate droplets and a long HPLC capillary connects the generator with both a capillary-based thermocycler and a capillary-based cytometer. The performance of the system is validated by absolute quantification of a gene specific to lung cancer (LunX). The results show that this system has very good linearity (0.9988) at concentrations ranging from NTC to 2.4 × 10^-4 copies per μL. As compared to qPCR, the all-in-one scheme is superior both in terms of the detection limit and the smaller fold changes measurement. The system of ddPCR might provide a powerful approach for clinical or academic applications where rare events are mostly considered.

Online Ozonolysis Combined with Ion Mobility-Mass Spectrometry Provides a New Platform for Lipid Isomer Analyses

One of the most significant challenges in contemporary lipidomics lies in the separation and identification of lipid isomers that differ only in site(s) of unsaturation or geometric configuration of the carbon-carbon double bonds. While analytical separation techniques including ion mobility spectrometry (IMS) and liquid chromatography (LC) can separate isomeric lipids under appropriate conditions, conventional tandem mass spectrometry cannot provide unequivocal identification. To address this challenge, we have implemented ozone-induced dissociation (OzID) in-line with LC, IMS, and high resolution mass spectrometry. Modification of an IMS-capable quadrupole time-of-flight mass spectrometer was undertaken to allow the introduction of ozone into the high-pressure trapping ion funnel region preceding the IMS cell. This enabled the novel LC-OzID-IMS-MS configuration where ozonolysis of ionized lipids occurred rapidly (10 ms) without prior mass-selection. LC-elution time alignment combined with accurate mass and arrival time extraction of ozonolysis products facilitated correlation of precursor and product ions without mass-selection (and associated reductions in duty cycle). Unsaturated lipids across 11 classes were examined using this workflow in both positive and negative ion modalities, and in all cases, the positions of carbon-carbon double bonds were unequivocally assigned based on predictable OzID transitions. Under these conditions, geometric isomers exhibited different IMS arrival time distributions and distinct OzID product ion ratios providing a means for discrimination of cis/trans double bonds in complex lipids. The combination of OzID with multidimensional separations shows significant promise for facile profiling of unsaturation patterns within complex lipidomes including human plasma.

Chemical characterization and evaluation of the antioxidants in Chaenomeles fruits by an improved HPLC-TOF/MS coupled to an on-line DPPH-HPLC method

An improved method based on HPLC-TOF/MS was developed to catalog the antioxidants in five species of Chaenomeles (Mugua). Forty-four fractions from the Mugua extracts show appreciable levels of antioxidative activity in scavenging the stable free-radical 2,2-diphenyl-1-picrylhydrazyl and the hydroxyl radicals. Twelve major antioxidant's chemical structures are identified. Antioxidant activities differ between species, but intra-species level of antioxidants, regardless of their ripeness, are similar. C. sinensis has the highest antioxidant level. A rigorous quality control procedure was implemented to ensure accuracy of antioxidant quantification. This improved procedure can be used for rapid discovery of antioxidants in other plant extracts.

The Impact of Lipophilicity in Drug Discovery: Rapid Measurements by Means of Reversed-Phase HPLC

Lipophilicity constitutes a vital physicochemical property in drug design as it is connected with pharmacodynamic and pharmacokinetic properties as well as toxicological aspects of candidate drugs. Traditional partitioning experiments to determine n-octanol-water coefficients are laborious and time-consuming, while they cannot be reliably performed for highly lipophilic or compounds undergoing degradation. Alternatively, lipophilicity of candidate drugs can be accurately and reproducibly determined using reversed-phase liquid chromatography. In this chapter, the details of protocols for lipophilicity assessment using reversed-phase HPLC, under conditions which provide the best simulation of n-octanol-water partition coefficients, are described.

Application of Six Sigma Model to Evaluate the Analytical Quality of Four HbA1c Analyzers

BACKGROUND

The Six Sigma Model is a global quality management system applicable to the determination of glycated hemoglobin (HbA1c). In addition, this model can ensure the three characteristics influencing the patient risk: the correct performance of the analytical method with low inaccuracy and bias, the quality control strategy used by the laboratory, and the necessary quality of the analyte. The aim of this study is to use the Six Sigma Model for evaluating quality criteria in the determination of glycated hemoglobin HbA1c and its application to assess four different HbA1c analyzers.

METHODS

Four HbA1c analyzers were evaluated: HA-8180V®, D-100®, G8®, and Variant II Turbo®. For 20 consecutive days, two levels of quality control (high and low) provided by the manufacturers were measured in each of the instruments. Imprecision (CV), bias, and Sigma values (σ) were calculated with the data obtained and a method decision chart was developed considering a range of quality requirements (allowable total error, TEa).

RESULTS

For a TEa = 3%, HA-8180V = 1.54 σ, D-100 = 1.63 σ, G8 = 2.20 σ, and Variant II Turbo = -0.08 σ. For a TEa = 4%, HA-8180V = 2.34 σ, D-100 = 2.32 σ, G8 = 3.74 σ, and Variant II Turbo = 0.16 σ. For a TEa = 10%, HA8180V = 7.12 σ, D-100 = 6.46 σ, G8 = 13.0 σ, and Variant II Turbo = 1.56 σ.

CONCLUSIONS

Applying the Stockholm consensus and its subsequent Milan review to the results: the maximum level in quality requirements for HbA1c is an allowable total error (TEa) = 3%, G8 is located in region 2 σ (2.20), which is a poor result, and HA-8180V and D-100 are both in region 1 σ (1.54 and 1.63, respectively), which is an unacceptable analytical performance.

Bioanalytical methods for the quantification of hydromorphone, fentanyl, norfentanyl, morphine, morphine-3ß-glucuronide and morphine-6ß-glucuronide in human plasma

The aim of this study was to develop an assay for the quantification of hydromorphone, morphine, fentanyl and the metabolites norfentanyl, morphine-3ß-glucuronide and morphine-6ß-glucuronide in human plasma to support pharmacokinetic studies investigating the large interpatient variability in response to opioid treatment. For the quantitation of hydromorphone, morphine, fentanyl and its metabolite norfentanyl aliquots of 200μL human potassium EDTA plasma were deproteinized with deuterated internal standards in a mixture of acetonitrile and acetone, followed by a liquid-liquid extraction with 4% ammonium hydroxide and ethyl acetate. Morphine-3ß-glucuronide and morphine-6ß-glucuronide were extracted by a solid phase extraction using 10mM ammonium carbonate pH 8.8 and a deuterated internal standards solution. Morphine, hydromorphone, fentanyl and norfentanyl were separated on an Aquity UPLC^® BEH C18 column 1.7μm, 100mm×2.1mm at 50°C. Separation, was achieved on a gradient of methanol with an overall run time of 6min. The compounds were quantified by triple-quadrupole mass spectrometry in the positive ion electrospray ionization mode. Morphine-3ß-glucuronide and morphine-6ß-glucuronide were separated on a VisionHT C18-P; 3μm 2.1×50mm, column at 40°C on a gradient of acetonitrile, with an overall run time of 10min. Both methods were precise and accurate, with within-run and between-run precisions within acceptable limits and accuracy ranging from 84.0 to 105.5%. The methods were successfully applied to support clinical pharmacological studies in patients treated with opioids for the treatment of moderate to severe cancer-related pain.

Ultra-High-Throughput Analytical Strategy Based on UHPLC-DAD in Combination with Syringe Filtration for the Quantitation of Nine Synthetic Colorants in Beverages: Impacts of Syringe Membrane Types and Sample pH on Recovery

An ultra-high-throughput approach based on ultra-high-performance liquid chromatography with diode array detection (UHPLC-DAD) in combination with simple syringe filtration was successfully developed and validated for the quantitation of nine synthetic colorants in beverages. The recoveries of the colorants from the beverages were found to be dramatically affected by the syringe filter membrane types and pH of the sample solution. The high recoveries of the nine colorants (92.7-105.9%) were achieved by syringe filtration with poly(vinylidene difluoride) membrane following the pH adjustment of sample solution at pH 7.0. The sample treatment procedure was very simple and took only 1 min. The fast chromatographic separation (1 min) of the nine synthetic colorants was achieved by UHPLC-DAD using a C18-core-shell column. This analytical approach (UHPLC-DAD combined with syringe filtration) took only approximately 3 min. The established method was ultrafast, sensitive, precise, accurate, and reliable. The method was successfully applied to rapidly determine the 9 colorants in 17 beverages.

Cytotoxicity mechanisms in melanoma cells and UPLC-QTOF/MS2 chemical characterization of two Brazilian stingless bee propolis: Uncommon presence of piperidinic alkaloids

The present study characterized propolis extracts produced by Scaptotrigona bipunctata (Tubuna) and Melipona quadrifasciata (Mandaçaia) by LC-MS/MS; their cytotoxicity as well as the mechanism of action in a melanoma cellular model were also assessed. The chemical characterization performed by UPLC-ESI-QTOF/MS² analysis revealed uncommon presence of piperidinic alkaloids in Tubuna's propolis extract together with C-glycopyranoside flavonoids. Mandaçaia's propolis collected in the same area rather presented terpenoids and flavonoids. Regarding the mechanism of cytotoxicity, propolis extracts increased the accumulation of reactive oxygen species (ROS), reduced the potential of mitochondrial membrane, induced a decrease in the proteins Bcl-2 and AKT-3 levels, and decreased melanoma cells' migration and invasion. Both propolis extracts induced apoptosis while only Mandaçaia's propolis extract induced cell cycle arrest in G2/M.

Fast Extraction and Detection of 4-Methylimidazole in Soy Sauce Using Magnetic Molecularly Imprinted Polymer by HPLC

On the basis of magnetic molecularly imprinted polymer (MMIP) solid-phase extraction coupled with high performance liquid chromatography, we established a new method for the determination of the 4-methylimidazole (4-MEI) in soy sauce. Scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM) were used to characterize the synthesized MMIPs. To evaluate the polymers, batch rebinding experiments were carried out. The binding strength and capacity were determined from the derived Freundlich isotherm (FI) equation. The selective recognition capability of MMIPs was investigated with a reference compound and a structurally similar compound. As a selective pre-concentration sorbents for 4-methylimidazole in soy sauce, the MMIPs showed a satisfied recoveries rate of spiked samples, ranged from 97% to 105%. As a result, the prepared MMIPs could be applied to selectively pre-concentrate and determine 4-methylimidazole in soy sauce samples.

How High Pressure Unifies Solvation Processes in Liquid Chromatography

A series of core-shell-based stationary phases of varying surface chemistry were subjected to solvent adsorption investigation under ultra-HPLC conditions. Acetonitrile and water excess isotherms were measured using a minor disturbance method. It was observed that adsorption of organic solvent is unified under high pressure. Preferential solvation due to specific interactions between the stationary phases and solvent molecules was limited. The obtained results showed that the solvation process is almost independent of surface chemistry, in contrast to HPLC conditions in which specific interactions differentiate solvation processes.

Validation of an LC-MS/MS assay to simultaneously monitor the intracellular active metabolites of tenofovir, emtricitabine, and lamivudine in dried blood spots

The ability to monitor adherence to antiretroviral therapy is critical for the interpretation of outcomes from clinical studies of HIV, and for optimizing patient care. The antiretrovirals tenofovir (TFV), emtricitabine (FTC), and lamivudine (3TC) are commonly included in drug regimens for HIV prevention and treatment. The active form of the drugs tenofovir diphosphate (TFVdp), emtricitabine triphosphate (FTCtp), and lamivudine triphosphate (3TCtp) are found intracellularly in erythrocytes and peripheral blood mononuclear cells (PBMCs). The ability to collect and analyze dried blood spot (DBS) samples is an attractive alternative to PBMC sampling in many resource limited settings. We developed and validated an assay to quantify all three intracellular metabolites over the range of 100-25000 fmol/sample. This assay utilizes a simple protein precipitation/liquid-liquid extraction of a single 3-mm DBS punch (from a Whatman 903 Protein Saver card) with isotopically labeled ¹³C₅-TFVdp included as the internal standard. Following extraction, samples are analyzed by anion exchange chromatography on a Thermo Biobasic AX 5μm column with detection by electrospray ionization in the positive mode on a AB Sciex API-5000 triple quadrupole mass spectrometer with a total run time of 8min. The assay was linear over the entire range (R²>0.996). The assay was accurate (inter-assay%bias within ±3.0%) and precise (inter-assay % CV≤9.8%). The assay was also reproducible from multiple punches within a spot as well as punches from separate blood spots. Stability was established at room temperature for 3days, and at -80°C for up to 63days. Clinical samples were analyzed from subjects on Truvada^®, Stribild^®, Descovy^®, and Triumeq^® regimens and intracellular metabolites were detected in all samples as expected, indicating the assay performs well for all current formulations of TFV, FTC, and 3TC.

Phytochemical and analytical characterization of constituents in Urceola rosea (Hook. & Arn.) D.J. Middleton leaves

In Vietnam and China the leaves of Urceola rosea are widely used as herbal remedy and food. However, in contrast to the plants stem, little information was available on major constituents. In this study, the first in-depth phytochemical investigation of U. rosea leaves is described, which resulted in the isolation of thirteen compounds, mainly flavonoids (kaempferol and quercetin derivatives) and triterpenes. Furthermore, an analytical procedure for the quantification of five major compounds was developed. The HPLC separation was performed on a Synergi MAX-RP column using acetonitrile and 0.1% formic acid as mobile phase. Method validation confirmed that the assay shows good linearity (R²≥0.9997), precision (intra-day R.S.D≤4.31%, inter-day R.S.D≤3.52%) and accuracy (recovery rates ranged from 96.8 to 102.6%). Detection limits were always lower than 0.07μg/mL. The analysis of several plant samples revealed distinct differences, as for example the content of total phenolics varied from 0.44 to 1.73%.

Automated cassette-based production of high specific activity [203/212Pb]peptide-based theranostic radiopharmaceuticals for image-guided radionuclide therapy for cancer

A method for preparation of Pb-212 and Pb-203 labeled chelator-modified peptide-based radiopharmaceuticals for cancer imaging and radionuclide therapy has been developed and adapted for automated clinical production. Pre-concentration and isolation of radioactive Pb2+ from interfering metals in dilute hydrochloric acid was optimized using a commercially-available Pb-specific chromatography resin packed in disposable plastic columns. The pre-concentrated radioactive Pb2+ is eluted in NaOAc buffer directly to the reaction vessel containing chelator-modified peptides. Radiolabeling was found to proceed efficiently at 85°C (45min; pH 5.5). The specific activity of radiolabeled conjugates was optimized by separation of radiolabeled conjugates from unlabeled peptide via HPLC. Preservation of bioactivity was confirmed by in vivo biodistribution of Pb-203 and Pb-212 labeled peptides in melanoma-tumor-bearing mice. The approach has been found to be robustly adaptable to automation and a cassette-based fluid-handling system (Modular Lab Pharm Tracer) has been customized for clinical radiopharmaceutical production. Our findings demonstrate that the Pb-203/Pb-212 combination is a promising elementally-matched radionuclide pair for image-guided radionuclide therapy for melanoma, neuroendocrine tumors, and potentially other cancers.

Measuring proteins with greater speed and resolution while reducing sample size

A multi-angle light scattering (MALS) system, combined with chromatographic separation, directly measures the absolute molar mass, size and concentration of the eluate species. The measurement of these crucial properties in solution is essential in basic macromolecular characterization and all research and production stages of bio-therapeutic products. We developed a new MALS methodology that has overcome the long-standing, stubborn barrier to microliter-scale peak volumes and achieved the highest resolution and signal-to-noise performance of any MALS measurement. The novel design simultaneously facilitates online dynamic light scattering (DLS) measurements. As National Institute of Standards and Technology (NIST) new protein standard reference material (SRM 8671) is becoming the benchmark molecule against which many biomolecular analytical techniques are assessed and evaluated, we present its measurement results as a demonstration of the unique capability of our system to swiftly resolve and measure sharp (20~25 µL full-width-half-maximum) chromatography peaks. Precise measurements of protein mass and size can be accomplished 10 times faster than before with improved resolution. In the meantime the sample amount required for such measurements is reduced commensurately. These abilities will have far-reaching impacts at every stage of the development and production of biologics and bio-therapeutic formulations.

Enantiomeric-Enriched Ferrocenes: Synthesis, Chiral Resolution, and Mathematic Evaluation of CD-chiral Selector Energies with Ferrocene-Conjugates

Enantiomeric-enriched ferrocene-modified pyrazoles were synthesized via the reaction of the ferrocene alcohol, (S)-FcCH(OH)CH₃ (Fc = ferrocenyl), with various pyrazoles in acidic conditions at room temperature within several minutes. X-ray structural data for racemic (R,S)-1N-(3,5-dimethyl pyrazolyl)ethyl ferrocene (1) and its (S)-enantiomer (S)-1 were determined. A series of racemic pyrazolylalkyl ferrocenes was separated into enantiomers by analytical HPLC on β- and γ-cyclodextrins (CD) chiral stationary phases. The quantum chemical calculations of interaction energies of β-CD were carried out for both (R)- and (S)-enantiomers. A high correlation between experimental HPLC data and calculated interaction energies values was obtained.

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).

Application of Mobile Phases Containing Ionic Liquid for HPLC Analysis of Selected Isoquinoline Alkaloids

An HPLC procedure on a polar reversed-phase column with mobile phases containing ionic liquid (IL) was developed for the analysis of selected alkaloids from different chemical groups. We aimed to obtain optimal conditions for the separation of alkaloids because widely used silica-based stationary phases exhibit a silanol effect, rendering analysis of basic analytes extremely difficult. Retention, separation selectivity, peak symmetry, and system efficiency were examined in various eluent systems containing different concentrations of IL and acetonitrile. The obtained results revealed substantial influence from the concentrations of IL, the organic modifier, and temperature on the retention behavior of the investigated alkaloids. The most selective and efficient chromatographic systems were applied for the analysis of several alkaloids in a plant extract.