A boronic acid-modified C60 derivatization reagent for the rapid detection of 3-monochloropropane-1,2-diol using matrix-assisted laser desorption/ionization-mass spectrometry

RATIONALE

3-Monochloropropane-1,2-diol (3-MCPD) is a well-known contaminant formed in food thermal processing, which could be found in a variety of foodstuffs. Due to its potential carcinogenicity, it was essential to quickly develop a rapid and high-throughput analytical method to monitor 3-MCPD in foodstuffs, which is described in this study.

METHODS

3-MCPD was extracted from foodstuffs and then was derivatized with a boronic acid-modified C₆₀ (B-C₆₀ ) through the boronic acid-diol reaction. Microwave heating was used to accelerate the derivatization reaction. Mass spectrometry (MS) analysis was conducted using matrix-assisted laser desorption/ionization-MS (MALDI-MS). The application of the method was validated using various smoked food samples.

RESULTS

The chemical derivatization of 3-MCPD with B-C₆₀ enabled the addition of a C₆₀ -tag to 3-MCPD. High-throughput analysis of the sample within 0.5 h was realized. A good linear range from 0.02 to 1.5 μg mL^-1 for 3-MCPD was obtained, with a detection limit of 0.005 μg mL^-1 . The recoveries in spiked foodstuffs ranged from 85.4% to 115.1% with relative standard deviations of 2.0%-14.2%. This method was successfully applied to detect 3-MCPD in smoked foodstuffs.

CONCLUSIONS

A quantitative method was developed for the detection of 3-MCPD in foodstuffs using B-C₆₀ derivatization combined with MALDI-MS strategy. This proposed method may serve as a potential platform for the rapid and high-throughput analysis of 3-MCPD in foodstuffs for the purpose of food safety control.

C60-based chemical labeling strategy for the determination of polyamines in biological samples using matrix-assisted laser desorption/ionization mass spectrometry

Bioactive polyamines play important roles in many biological processes such as gene expression, cell growth, protein synthesis, and signal transduction. Accurate determination of polyamines is helpful for studying their biological functions. Herein, a C₆₀-based chemical labeling strategy was proposed for the determination of polyamines (putrescine, cadaverine, spermidine, and spermine) in biological samples using matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS). An N-hydroxysuccinimide ester functionalized C₆₀ (NHS-C₆₀) was used as a labeling reagent and the m/z of the labeled polyamines reached up to more than 900 Da, which avoided matrix interferences in the low m/z region. In addition, as NHS-C₆₀ derivatives, mono- and bis-substituted polyamines were produced simultaneously, which benefited the qualitative analysis of polyamines. The analytical method was validated using NHS-C₆₀ labeled polyamines in cells and mice feces samples. Good linearities were obtained with correlation coefficients ranging from 0.9786 to 0.9982. The limits of quantification were in the range of 0.68-1.48 pmol. Good reproducibility and reliability of our proposed method were confirmed by intra- and inter-day precisions ranged from 2.8 to 16.6%, and the recoveries ranged between 81.8 and 119.9%. Finally, the proposed method was applied to determine polyamines in cells and mice feces. Three polyamines were detected in the cells, and the contents of cadaverine and spermidine in the feces of high-fat diet mice were found to be significantly lower than those in the normal diet mice. The results show that the proposed NHS-C₆₀ labeling coupled with MALDI MS strategy is suitable for the determination of polyamines in biological samples.

Boron Isotope Tag-Assisted Ultrahigh-Performance Liquid Chromatography Coupled with High-Resolution Mass Spectrometry for Discovery and Annotation of cis-Diol-Containing Metabolites

cis-Diol-containing metabolites are widely distributed in living organisms, and they participate in the regulation of various important biological activities. The profiling of cis-diol-containing metabolites could help us in fully understanding their functions. In this work, based on the characteristic isotope pattern of boron, we employed a boronic acid reagent as the isotope tag to establish a sensitive and selective liquid chromatography-high-resolution mass spectrometry method for the screening and annotation of cis-diol-containing metabolites in biological samples. Boronic acid reagent 2-methyl-4-phenylaminomethylphenylboronic acid was used to label the cis-diol-containing metabolites in biological samples to improve the selectivity and MS sensitivity of cis-diol-containing metabolites. Based on the characteristic 0.996 Da mass difference of precursor ions and the peak intensity ratio of 1:4 originating from ¹⁰B and ¹¹B natural isotopes, the potential cis-diol-containing metabolites were rapidly screened from biological samples. Potential cis-diol-containing metabolites were annotated by database searching and analysis of fragmentation patterns obtained by multistage MS (MSⁿ) via collision-induced dissociation. Importantly, the cis-diol position could be readily resolved by the MS³ spectrum. With this method, a total of 45 cis-diol-containing metabolites were discovered in rice, including monoglycerides, polyhydroxy fatty acids, fatty alcohols, and so forth. Furthermore, the established method showed superiority in avoiding false-positive results in profiling cis-diol-containing metabolites.

[Morphological changes of the central sulcus in children with complete growth hormone deficiency: a 3.0 T MRI study]

Objective: To analyze morphological changes in central sulcus of the cerebral cortex in children with complete growth hormone deficiency (CGHD). Methods: Patients attending the Shandong Provincial Hospital who were diagnosed with CGHD or idiopathic short stature were recruited from January 2015 to January 2019. Thirty children with CGHD (18 males and 12 females, 5 to 14 years old) and 30 children with idiopathic short stature (22 males and 8 females, 5 to 14 years old) were included. Measurements of the central sulcus, including the average width, maximum depth, average depth, top length, bottom length and depth position-based profiles (DPP), were obtained using Brain VISA software. The significant differences between groups were statistically analyzed. Results: The average width of bilateral central sulci in children with CGHD (left: (2.26±0.41) mm; right: (2.19±0.34) mm) were significantly higher than those in children with idiopathic short stature (left: (2.10±0.27) mm; right: (2.02±0.18) mm) (P<0.05) ; The maximum depth of the left central sulcus ((19.67±1.29) mm) and the average depth of the right central sulcus ((14.18±1.41) mm) were significantly lower than those in children with idiopathic short stature (left maximum depth: (20.69±1.43) mm; right average depth: (14.92±1.21) mm) (P<0.05) . Children with CGHD had significantly lower DPP at the middle part of the left central sulcus (sites: 46-54) and the inferior part of the right central sulcus(sites: 91-98). Conclusion: There are significant morphological changes of the central sulcus in children with CGHD, which may represent the structural basis of their relatively slower development in motor, cognitive and linguistic functional performance.

Development of C60-based labeling reagents for the determination of low-molecular-weight compounds by matrix assisted laser desorption ionization mass spectrometry (II): Determination of thiols in human serum

Perturbation of thiol homeostasis in biological fluids are thought to be associated with several diseases, and reliable analytical methods for the determination of low molecular weight (LMW) thiols in human plasma or serum are thus required. In this study, a matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) method is described for high throughput determination of four LMW thiols (glutathione, cysteine, homocysteine and cysteinylglycine) in human serum. It is based on the use of a bromoacetyl functionalized C60 (Br-C60) as a derivatization reagent to label thiols. The Br-C60 labeling can add an 832-Da tag to thiols, which moves thiol signals to high mass region and effectively avoids the signal interference generated by the traditional MALDI matrix below 800 Da. The labeling can be completed within 5 min under microwave-assisted condition. Thereby, the Br-C60 labeling based MALDI-TOF MS analytical method can achieve high throughput analysis of LMW thiols in serum. Good linearities of the method for the thiols in human serum were obtained in the range of 0.5-500.0 μM with correlation coefficient (R) greater than 0.9960. The limit of detection is in the range of 0.07-0.18 μM for the investigated thiols in human serum with relative standard deviations of lower than 13.5% and recoveries ranging from 81.9 to 117.1%. Using the method, four thiols in microliter serum samples of breast cancer (BC) patients were determined. The result showed that the contents of the four thiols in BC serum samples significantly changed compared to the healthy control (HC).

[The relationship between accommodative accuracy at different near-work distances and early-onset myopia]

OBJECTIVE

To observe the accommodative accuracy of children with early-onset myopia at different near-work distances, and discuss the relationship between accommodative accuracy and early-onset myopia.

METHODS

This was a case-control study. Thirty-seven emmetropic children, 41 early-onset myopic children without correction, and 39 early-onset myopic children with spectacles, aged 7 to 13 years, were included. Measures of refractive errors and accommodative accuracy at four near-work distances, including 50 cm, 40 cm, 30 cm, and 20 cm, were made using the binocular fusion cross cylinder (FCC) of an automatic phoropter.

RESULTS

Most candidates showed accommodative lags, including the children with emmetropia. The ratio of lags in all candidates at different near-work distances was 75.21% (50 cm), 87.18% (40 cm), 92.31% (30 cm), and 98.29% (20 cm), respectively. All accommodative accuracies became worse, and the accommodative lag ratio and values of FCC increased, along with the shortening of the distance. The difference in accommodative accuracy among groups was statistically significant at 30 cm (χ(2)=7.852, P= 0.020) and 20 cm (χ(2)=6.480, P=0.039). The values of FCC among groups were significantly different at 30 cm (F=3.626, P=0.030) and 20 cm (F=3.703, P=0.028), but not at 50 cm and 40 cm (P>0.05). In addition, the FCC values of 30 cm and 20 cm had a statistically significant difference between myopic children without correction [(1.25±0.44) D and (1.76±0.43) D] and emmetropic children [(0.95±0.52) D and (1.41±0.58) D] (P=0.012, 0.008). The correlation between diopters of myopia and accommodative accuracy at different nearwork distances was not statistically significant (P>0.05). However, the correlation between diopters of myopia and the accommodative lag value (FCC) at 20 cm was statistically significant (r=0.246, P=0.028).

CONCLUSIONS

The closer the near-work distance is, the worse the accommodative accuracy is. This is more significant in early-onset myopia, especially myopia without correction, than emmetropia. Wearing spectacles may improve the threshold and sensitivity of accommodations, and the accommodative accuracy at near-work distances (<30 cm) to some extent. The poor accommodative accuracy at near-work distances may be not related to early-onset myopia, but the value of FCC (20 cm) is related to early-onset myopia. The higher the FCC value is, the higher the diopter is. (Chin J Ophthalmol, 2016, 52: 520-524).

Nickel Oxide Nanoparticle-Deposited Silica Composite Solid-Phase Extraction for Benzimidazole Residue Analysis in Milk and Eggs by Liquid Chromatography-Mass Spectrometry

A novel nickel oxide nanoparticle-deposited silica (SiO2@NiO) composite was prepared via liquid-phase deposition (LPD) and then employed as a solid-phase extraction (SPE) sorbent. When the SPE was coupled with liquid chromatography-electrospray ionization mass spectrometry (LC-ESI/MS) analysis, an analytical platform for the sensitive determination of benzimidazole residues in egg and milk was established. The limits of detection of nine benzimidazoles were in the range of 0.8-2.2 ng/mL in milk and 0.3-2.1 ng/g in eggs, respectively, which was 5-10 times superior to the methods with other adsorbents for SPE. The recoveries of nine benzimidazoles spiked in milk and egg ranged from 70.8 to 118.7%, with relative standard deviations (RSDs) being less than 18.9%. This work presented the excellent extraction performance of NiO on benzimidazoles for the first time, and the applicability of the LPD technique used as sorbents for trace analysis in complex matrices was also demonstrated.

Profiling of aldehyde-containing compounds by stable isotope labelling-assisted mass spectrometry analysis

We developed a strategy for non-targeted profiling of aldehyde-containing compounds by stable isotope labelling in combination with liquid chromatography-double neutral loss scan-mass spectrometry (SIL-LC-DNLS-MS) analysis. A pair of stable isotope labelling reagents (4-(2-(trimethylammonio)ethoxy)benzenaminium halide, 4-APC and d4-4-(2-(trimethylammonio)ethoxy)benzenaminium halide, 4-APC-d4) that can selectively label aldehyde-containing compounds were synthesized. The 4-APC and 4-APC-d4 labelled compounds were capable of generating two characteristic neutral fragments of 87 Da and 91 Da, respectively, under collision induced dissociation (CID). Therefore, double neutral loss scans were carried out simultaneously to record the signals of the potential aldehyde-containing compounds. In this respect, the aldehyde-containing compounds from two samples labelled with 4-APC and 4-APC-d4 were ionized at the same time but recorded separately by mass spectrometry. The peak pairs with characteristic mass differences (n × 4 Da) can be readily extracted from the DNLS spectra and assigned as potential aldehyde-containing candidates, which facilitates the identification of the target aldehydes. 4-APC and 4-APC-d4 labelling also dramatically increased detection sensitivities of the derivatives. Using the SIL-LC-DNLS-MS strategy, we successfully profiled the aldehyde-containing compounds in human urine and white wine. Our results showed that 16 and 19 potential aldehyde-containing compounds were discovered in human urine and white wine, respectively. In addition, 5 and 4 aldehyde-containing compounds in human urine and white wine were further identified by comparison with aldehyde standards. Altogether, SIL-LC-DNLS-MS demonstrated to be a promising approach in the identification and relative quantification of aldehyde-containing compounds from complex samples.

Use of Pollen Solid-Phase Extraction for the Determination of trans-Resveratrol in Peanut Oils

In this study, a simple and convenient method for the determination of trans-resveratrol (TRA) in peanut oils based on pollen grain solid-phase extraction (SPE) was developed. Pollen grains were used as normal-phase SPE sorbent to separate TRA from peanut oils for the first time. As a naturally occurring material, pollen grains exhibited an excellent adsorption capacity for polyphenolic compounds due to their particular functional structures such as hydroxyl groups, saturated and unsaturated aliphatic chains with aromatics. Their stable compositions as well as adequate particle size (30-40 μm) also make them suitable for SPE. Several parameters influencing extraction performance were investigated. Coupled with high-performance liquid chromatography-ultraviolet detection (HPLC-UV), a green purification method for fast determination of TRA in peanut oils using pollen grain cartridges as sorbents was established. The linearity range of the proposed method was 10-2500 ng · g(-1) with a satisfactory correlation coefficient (r(2)) of 0.9999. The limit of detection (LOD) for TRA in peanut oils was 2.7 ng · g(-1), and the recoveries in spiked oil samples were from 70.2% to 98.4% with the relative standard deviations (RSDs) less than 4.9% (intraday) and 5.2% (interday). This method was successfully applied to the analysis of TRA in several peanut oils with different brands from local market as well as other kinds of vegetable oils.

Magnetic solid phase extraction coupled with desorption corona beam ionization-mass spectrometry for rapid analysis of antidepressants in human body fluids

A rapid analysis method by coupling magnetic solid phase extraction (MSPE) with desorption corona beam ionization (DCBI) is presented.

Sequential enrichment with titania-coated magnetic mesoporous hollow silica microspheres and zirconium arsenate-modified magnetic nanoparticles for the study of phosphoproteome of HL60 cells

As one of the most important types of post-translational modifications, reversible phosphorylation of proteins plays crucial roles in a large number of biological processes. However, owing to the relatively low abundance and dynamic nature of phosphorylation and the presence of the unphosphorylated peptides in large excess, phosphopeptide enrichment is indispensable in large-scale phosphoproteomic analysis. Metal oxides including titanium dioxide have become prominent affinity materials to enrich phosphopeptides prior to their analysis using liquid chromatography-mass spectrometry (LC-MS). In the current study, we established a novel strategy, which encompassed strong cation exchange chromatography, sequential enrichment of phosphopeptides using titania-coated magnetic mesoporous hollow silica microspheres (TiO2/MHMSS) and zirconium arsenate-modified magnetic nanoparticles (ZrAs-Fe3O4@SiO2), and LC-MS/MS analysis, for the proteome-wide identification of phosphosites of proteins in HL60 cells. In total, we were able to identify 11,579 unique phosphorylation sites in 3432 unique proteins. Additionally, our results suggested that TiO2/MHMSS and ZrAs-Fe3O4@SiO2 are complementary in phosphopeptide enrichment, where the two types of materials displayed preferential binding of peptides carrying multiple and single phosphorylation sites, respectively.

Mesostructured nanomagnetic polyhedral oligomeric silsesquioxanes (POSS) incorporated with dithiol organic anchors for multiple pollutants capturing in wastewater

A functionalizable organosiliceous hybrid magnetic material was facilely constructed by surface polymerization of octavinyl polyhedral oligomeric silsesquioxane (POSS) on the Fe3O4 nanoparticles. The resultant Fe3O4@POSS was identified as a mesoporous architecture with an average particle diameter of 20 nm and high specific surface area up to 653.59 m(2) g(-1). After it was tethered with an organic chain containing dithiol via thiol-ene addition reaction, the ultimate material (Fe3O4@POSS-SH) still have moderate specific area (224.20 m(2) g(-1)) with almost identical porous morphology. It turns out to be a convenient, efficient single adsorbent for simultaneous elimination of inorganic heavy metal ions and organic dyes in simulate multicomponent wastewater at ambient temperature. The Fe3O4@POSS-SH nanoparticles can be readily withdrawn from aqueous solutions within a few seconds under moderate magnetic field and exhibit good stability in strong acid and alkaline aqueous matrices. Contaminants-loaded Fe3O4@POSS-SH can be easily regenerated with either methanol-acetic acid (for organic dyes) or hydrochloric acid (for heavy metal ions) under ultrasonication. The renewed one keeps appreciable adsorption capability toward both heavy metal ions and organic dyes, the removal rate for any of the pollutants exceeds 92% to simulate wastewater with multiple pollutants after repeated use for 5 cycles. Beyond the environmental remediation function, thanks to the pendant vinyl groups, the Fe3O4@POSS derived materials rationally integrating distinct or versatile functions could be envisaged and consequently a wide variety of applications may emerge.

Dispersive microextraction based on "magnetic water" coupled to gas chromatography/mass spectrometry for the fast determination of organophosphorus pesticides in cold-pressed vegetable oils

This article presents a novel application of dispersive microextraction based on "magnetic water" (m-water) for the purification of organophosphorus pesticides (methamidophos, omethoate, monocrotophos) from cold-pressed vegetable oils. In the present study, a trace amount of water (extractant) was adsorbed on bare Fe₃O₄ by hydrophilic interaction to form m-water. Rapid extraction can be achieved while the m-water is dispersed in the sample solution with the aid of a vigorous vortex. After extraction, the analyte-adsorbed m-water can be readily isolated from the sample solution by a magnet, which could greatly simplify the operation and reduce the whole pretreatment time. Several parameters affecting the extraction efficiency were investigated, and under the optimized conditions, a simple and effective method for pesticide analysis was established by coupling with gas chromatography/mass spectrometry (GC/MS). The linearity range of the proposed method was 2-100 ng/g with satisfactory correlation coefficients (R) of 0.9997-0.9998, and the limits of quantification (LOQ) for the target compounds were in the range of 0.70-1.27 ng/g. In addition, the reproducibility was obtained by evaluating the intra- and interday precisions with relative standard deviations (RSDs) less than 7.2% and 6.5%, respectively. Finally, the established "magnetic water" microextraction method was successfully applied for the determination of pesticide residues in several kinds of cold-pressed vegetable oils.

Facile preparation of organic-silica hybrid monolith for capillary hydrophilic liquid chromatography based on "thiol-ene" click chemistry

In this work, a one-step approach to facile preparation of organic-inorganic hybrid monoliths was successfully developed. After vinyl-end organic monomers and azobisisobutyronitrile (AIBN) were mixed with hydrolyzed tetramethoxysilane (TMOS) and 3-mercaptopropyltrimethoxysilane (MPTMS), the homogeneous mixture was introduced into a fused-silica capillary for simultaneous polycondensation and "thiol-ene" click reaction to form the organic-silica hybrid monoliths. By employing this strategy, two types of organic-silica hybrid monoliths with positively charged quaternary ammonium and amide groups were prepared, respectively. The functional groups were successfully introduced onto the monoliths during the sol-gel process with "thiol-ene" click reaction, which was demonstrated by ζ-potential assessment, energy dispersive X-ray spectroscopy (EDX), and Fourier transform infrared (FT-IR) spectroscopy. The porous structure of the prepared monolithic columns was examined by scanning electron microscopy (SEM), nitrogen adsorption-desorption measurement, and mercury intrusion porosimetry. These results indicate the prepared organic-silica hybrid monoliths possess homogeneous column bed, large specific surface area, good mechanical stability, and excellent permeability. The prepared monolithic columns were then applied for anion-exchange/hydrophilic interaction liquid chromatography. Different types of analytes, including benzoic acids, inorganic ions, nucleosides, and nucleotides, were well separated with high column efficiency around 80,000-130,000 plates/m. Taken together, we present a facile and universal strategy to prepare organic-silica hybrid monoliths with a variety of organic monomers using one-step approach.

Multiresidue determination of (fluoro)quinolone antibiotics in chicken by polymer monolith microextraction and field-amplified sample stacking procedures coupled to CE-UV

Simultaneous determination of 9 (fluoro)quinolone antibiotics (FQs) was accomplished by capillary electrophoresis-ultraviolet (CE-UV) based on poly(methacrylic acid-co-ethylene glycol dimethacrylate) (MAA-EGDMA) monolith microextraction (PMME) coupled with on-line preconcentration technique of field-amplified sample stacking (FASS). The effects of composition of the acid and organic solvent in the sample solution, sampling time, and voltage on the efficiency of the sample stacking have been systematically investigated. Several parameters that influence extraction efficiency for PMME such as pH of sample solution, extraction volume, and wash and desorption conditions were optimized. In the proposed method, a substantial increase in sensitivity for all the FQs tested was achieved by the combination of PMME procedure with on-line preconcentration of FASS prior to CE analysis. Good linearities were obtained for the 9 tested FQs with the correlation coefficients (R) above 0.9954. The limits of detection (S/N=3) were found to be 2.4-34.0 ng g(-1) and the recoveries ranged from 81.2 to 100% with relative standard deviations less than 11.3%. The proposed PMME-FASS-CE method was applied to the determination of FQs residues in chicken samples.

HPLC separation of fullerenes on two charge-transfer stationary phases

Two charge-transfer stationary phases were prepared by immobilizing p-nitrobenzoic acid and naphthyl acetic acid onto silica. The nitrophenyl moiety and the naphthyl moiety were grafted to silica gel through the spacer of aminoalkyl silanes. The HPLC separation of C60, C70, and higher fullerenes on the new stationary phases was also studied. The influence of mobile phase and column temperature on the separation of C60 and C70 was examined, respectively. The retentions of C60 and C70 on the two stationary phases increased with decreasing toluene content in the mobile phase or with increasing column temperature. Higher fullerenes can be separated well using toluene as the mobile phase on the stationary phase of p-nitrobenzoic acid-bonded silica.

Humic acid-bonded silica as a novel sorbent for solid-phase extraction of benzo[a]pyrene in edible oils

A novel solid-phase extraction (SPE) sorbent, humic acid-bonded silica (HAS), was prepared. Humic acids (HAs) were grafted onto silica matrices via an amide linkage between humyl chloride and the amido terminus of 3-aminopropyltrimethoxysilane (APTS)-silica gel. The resulting material was characterized by Fourier transform infrared spectrometer, elemental analysis, and nitrogen adsorption analysis. This sorbent exhibits an excellent adsorption capacity for some electron-abundant analytes owing to its peculiar structure. In this paper, we choose benzo[a]pyrene (BaP) in oil as a probe to validate the adsorption capacity of the material. Thus a fast, cheap and simple SPE method with humic acid-bonded silica cartridge for edible oil clean-up, followed by high-performance liquid chromatography (HPLC) with fluorescence detection was established. The effects of experimental variables, such as washing and elution solvents, and the amount of sorbents have been studied. The recoveries of BaP in edible oils spiked at 0.2-100 microg kg(-1) were in the range of 78.8-102.7% with relative standard deviations ranging between 1.3 and 9.3%; the limit of detection was -0.06 microg kg(-1).

Synthesis and chromatographic properties of a chiral stationary phase derived from bovine serum albumin immobilized on magnesia-zirconia using phosphonate spacers

A novel bovine serum albumin (BSA)-modified magnesia-zirconia stationary phase was prepared using the sodium salt of cis-(3-methyloxiranyl)phosphonic acid (fosfomycin) as spacer and glutaraldehyde as coupler. Baseline separation of six derivatized amino acids (DNB-Leu, Dansyl-Val, etc.) was achieved on this column using ammonium acetate buffer-isopropanol mobile phase at a flow rate of 1.0 mL/min. The effects of mobile phase composition, eluent pH value, column temperature, and flow rate on the retention and separation of chiral compounds were also investigated. The BSA chiral stationary phase (BSA-CSP) was relatively stable under experimental conditions. The coupling reaction in this method was mild, reliable, and reproducible; thus it was also suitable for the immobilization of various biopolymers with amino groups in the preparation of chromatography stationary phases.

Multiresidue analysis of beta-agonists in pork by coupling polymer monolith microextraction to electrospray quadrupole time-of-flight mass spectrometry

A novel method of polymer monolith microextraction (PMME) using poly(methacrylic acid-co-ethylene glycol dimethacrylate) monolith combined with electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-QTOF MS) was developed for the rapid and sensitive determination of beta-agonists in pork samples. The conditions of PMME were optimized for the improvement of extraction efficiency and reduction of the matrix interferences from pork. Under the optimal condition, the eluate solution allowed direct analysis by mass spectrometry. In the positive ion mode and in the multiple reaction monitoring (MRM) mode, the limits of detection (LODs) for beta-agonists were found to be 0.08 ng/g (clenbuterol, CLB), 0.18 ng/g (salbutamol, SBTM) and 0.26 ng/g (terbutaline, TBTL) in pork, respectively, with good inter- and intra-day precisions (2-10% for CLB, 11-23% for SBTM and 4-16% for TBTL). The proposed PMME/ESI-QTOF MS method was successfully applied to the determination of beta-agonist residues in thirteen real samples, and the positive samples were confirmed according to the identification points (IPs) system defined by Commission Decision 2002/657/EC. To investigate the matrix effect, the proposed method was compared with PMME-HPLC/ESI-QTOF MS and the slight decrease in sensitivity of PMME/ESI-QTOF MS was ascribed to the inter-analyte ion suppression.

Determination of fluoroquinolones in eggs using in-tube solid-phase microextraction coupled to high-performance liquid chromatography

A simple, rapid, and sensitive method using in-tube solid-phase microextraction (in-tube SPME) based on poly(methacrylic acid-ethylene glycol dimethacrylate) (MAA-EGDMA) monolith coupled to HPLC with fluorescence and UV detection was developed for the determination of five fluoroquinolones (FQs). Ofloxacin (OFL), norfloxacin (NOR), ciprofloxacin (CIP), enrofloxacin (ENRO), and sarafloxacin (SARA) can be enriched and determined in the spiked eggs and albumins. CIP/ENRO in eggs and albumins of ENRO-treated hens were also studied using the proposed method. Only homogenization, dilution, and centrifugation were required before the sample was supplied to the in-tube microextraction, and no organic solvents were consumed in the procedures. Under the optimized extraction conditions, good extraction efficiency for the five FQs was obtained with no matrix interference in the process of extraction and the subsequent chromatographic separation. The detection limits (S/N=3) were found to be 0.1-2.6 ng g(-1) and 0.2-2.4 ng g(-1) in whole egg and egg albumin, respectively. Good linearity could be achieved over the range 2-500 ng mL(-1) for the five FQs with regression coefficients above 0.9995 in both whole egg and albumin. The reproducibility of the method was evaluated at three concentration levels, with the resulting relative standard deviations (RSDs) less than 7%. The method was successfully applied to the analysis of ENRO and its primary metabolite CIP in the eggs and albumins of ENRO-treated hens.

Preparation of pyrenebutyric acid bonded silica stationary phases for the application to the separation of fullerenes

A novel immobilization method was proposed for the preparation of pyrenebutyric acid-bonded silica (PYB-silica) stationary phases. The pyrene moiety was grafted to silica gel through spacers of aminoalkyl silanes. The HPLC separation of C60, C70 and higher fullerenes on the new pyrenebutyric acid-bonded silica stationary phases was also studied. Based on the temperature effect, the intermolecular interaction between stationary phases and solutes and the retention mechanism were discussed. The results of column loading capacity test demonstrated the potential for the separation of fullerenes in large amounts on the PYB-silica stationary phases.

New glutarimide antibiotics, S-632-B1 and B2. II. Isolation, physico-chemical properties and chemical structure

Antifungal antibiotics S-632-A1,A2,B1 and B2 were extracted with ethyl acetate from the filtered broth of Streptomyces hygroscopicus S-632 and isolated through a combination of conventional and reversed-phase silica gel column chromatography. On the basis of the spectral data, S-632-B1 and B2 were found to be new members of the glutarimide family of antibiotics. The chemical structures of these components were elucidated as two stereo-isomers of 3-(5,7-dimethyl-8,9-epoxy-2-hydroxy-4-oxo-6-decenyl)glutarimide.

New glutarimide antibiotics, S-632-B1 and B2. I. Taxonomy of producing strain, fermentation and biological properties

Strain S-632 was found to produce new glutarimide antibiotics, S-632-B1 and B2, which were isolated from the culture fluid. A taxonomic study on strain S-632 was carried out, and the taxonomic characterization demonstrated that it belonged to the species Streptomyces hygroscopicus. The strain was given the name S. hygroscopicus S-632. These antibiotics were active against Saccharomyces sp., but inactive against filamentous fungi and bacteria, and had cytotoxic activity against KB tissue culture cells.