A new solid-phase extraction and HPLC method for determination of patulin in apple products and hawthorn juice in China

A new solid‐phase extraction (SPE) pretreatment method using a home‐made polyvinylpolypyrrolidone‐florisil (PVPP‐F) column was developed for the analysis of patulin in apple and hawthorn products in China. Fifty samples (25 apple juices, 12 apple jams, and 13 hawthorn juices) were prepared using the new method and then analyzed by high performance liquid chromatography with diode array detection (HPLC‐DAD) on an Agela Venusil MP C₁₈ reversed‐phase column (4.6 mm × 250 mm, 5 μm). The cleanup results for all samples using home‐made PVPP‐F column were compared with those obtained using a MycoSep®228 AflaPat column. The correlation coefficient R (0.9998) fulfilled the requirement of linearity for patulin in the concentration range of 2.5–250 μg/kg. The limits of detection (LODs) and quantification (LOQs) of patulin were 3.99 and 9.64 μg/kg for PVPP‐F column, and 3.56 and 8.07 μg/kg for MycoSep®228 AflaPat column, respectively. Samples were spiked with patulin at levels ranging from 25 to 250 μg/kg, and recoveries using PVPP‐F and MycoSep®228 AflaPat columns were in the range of 81.9–100.9% and 86.4–103.9%, respectively. Naturally occurring patulin was found in 2 of 25 apple juice samples (8.0%) and 1 of 13 hawthorn juice samples (7.7%) at concentrations ranging from 12.26 to 36.81 μg/kg. The positive results were further confirmed by liquid chromatography electrospray ionization mass spectrometry (LC‐ESI‐MS).     

Determination of trace indium in urine after preconcentration with a chelating-resin-packed minicolumn

A simple and rapid chelating-resin-packed column has been developed for preconcentration of trace indium in biological samples. A large-sized urine sample was pumped through a minicolumn at a flow rate of 1.0 mL/min by using a peristaltic pump, and the eluents were analyzed using graphite furnace atomic absorption spectrometry (GFAAS). Four commercially available chelating resins including Chelex-100, Amberlite IRC-50, Duolite GT-73, and Celite 545-AW were studied for evaluating the indium sorption performance. Several parameters, such as pH, resin amount, eluent volume, eluent flow rate, and the volume of sample, were investigated and optimized. A 100-200 mL of the sample was loaded into a column containing 1.2 g of wet Chelex-100 and subjected to the ion-exchange procedure. The retained analytes were eluted with 5.0 mL of 0.1 M HNO(3) and quantified by GFAAS. The correlation coefficient in the range 10-250 ng/mL was of 0.9994. The limit of detection of the proposed method was 2.75 ng/mL. The method developed was successfully applied to analysis of spiked urine samples with good recoveries of 93-103% (n = 6) and reproducibility (relative standard deviation < 4.9%). The accuracy of procedure was confirmed by indium determination in spiked certified reference materials.     

Ultra-high pressure LC determination of glucosamine in shrimp by-products and migration tests of chitosan films

Chitosan, a multiple applications molecule, was isolated from shrimp by-products by fermentation. The amount of chitosan in the solid fraction of the fermented extract was measured after its conversion in the respective glucosamine units. The procedure includes an acid hydrolysis (110 °C, 4 h with HCl 8 M) and a derivatization with 9-fluorenylmethyl chloroformate (Fmoc-Cl). Ultra-high-pressure liquid chromatography method was developed and optimized. Excellent peaks resolution was achieved in just 10 min. The method was evaluated in what concerns to validation parameters such as linearity, repeatability, quantification limit, and recovery. Migration tests of films prepared with chitosan were carried out in two simulants: ultrapure water and ethanol 95% (v/v).     

Determination of the glycation sites of Bacillus anthracis neoglycoconjugate vaccine by MALDI-TOF/TOF-CID-MS/MS and LC-ESI-QqTOF-tandem mass spectrometry

We present herein an efficient mass spectrometric method for the localization of the glycation sites of a model neoglycoconjugate vaccine formed by a construct of the tetrasaccharide side chain of the Bacillus anthracis exosporium and the protein carrier bovine serum albumin. The glycoconjugate was digested with both trypsin and GluC V8 endoproteinases, and the digests were then analyzed by MALDI-TOF/TOF-CID-MS/MS and nano-LC-ESI-QqTOF-CID-MS/MS. The sequences of the unknown peptides analyzed by MALDI-TOF/TOF-CID-MS/MS, following digestion with the GluC V8 endoproteinase, allowed us to recognize three glycopeptides whose glycation occupancies were, respectively, on Lys 235, Lys 420, and Lys 498. Similarly, the same analysis was performed on the tryptic digests, which permitted us to recognize two glycation sites on Lys 100 and Lys 374. In addition, we have also used LC-ESI-QqTOF-CID-MS/MS analysis for the identification of the tryptic digests. However, this analysis identified a higher number of glycopeptides than would be expected from a glycoconjugate composed of a carbohydrate-protein ratio of 5.4:1, which would have resulted in glycation occupancies of 18 specific sites. This discrepancy was due to the large number of glycoforms formed during the synthetic carbohydrate-spacer-carrier protein conjugation. Likewise, the LC-ESI-QqTOF-MS/MS analysis of the GluC V8 digest also identified 17 different glycation sites on the synthetic glycoconjugate.     

Impact of substituent position in monosubstituted α-cyclodextrins on enantioselectivity in capillary electrophoresis

In this study, our three recently synthesized regiospecifically monosubstituted carboxymethyl-α-cyclodextrins (CMACDs) were successfully applied for the enantiomeric separation of several biologically important low-molecular weight compounds by capillary electrophoresis. The enantioselectivity of the individual monosubstituted CMACDs added into the background electrolyte (BGE) was studied and compared with the mixture of three monosubstituted CMACDs and with native α-cyclodextrin at pH of the BGE ranging from 2.5 to 11. Our experiments revealed a significant influence of the position of the carboxymethyl group on the α-cyclodextrin skeleton on the enantioselectivity for all the studied analytes. Interestingly, the least common 3(I)-O regioisomer was revealed as the most effective chiral selector.     

Accuracy mass screening and identification of phenolic compounds from the five parts of Abutilon theophrasti Medic. by reverse-phase high-performance liquid chromatography-electrospray ionization-quadrupoles-time of flight-mass spectrometry

A rapid and resolutive reverse-phase high-performance liquid chromatography-electrospray ionization-quadrupoles-time of flight-mass spectrometry method was established for the screening and identification of the phenolic compounds in the 70% ethanolic extracts from the five parts (roots, stems, leaves, seeds, and exocarps) of Abutilon theophrasti Medic.. Separation and detection conditions were optimized by using a 22 mixing standard, which included phenolic acids, flavonoids and a naphthalene compound. Optimum LC separation was achieved on a C(18) analytical column (250 mm x 4.6 mm id, 5 μm) by gradient elution with water containing 0.1% v/v formic acid (pH 2.4) and acetonitrile as mobile phases, at a flow rate of 1.0 mL/min. The developed method was applied to the study on the constituents of A. theophrasti Medic., and 16 compounds were unequivocally identified with standards. Meanwhile, 37 constituents were tentatively identified by comparing with references. In addition, accurate molecular formulae were conjectured for unknown compounds. To our knowledge, little is known about how these compounds are distributed in A. theophrasti Medic.. Hence, it is clear that the comprehensive analysis of the phenolic compounds of A. theophrasti Medic. is helpful for the quality control and understanding the usage and function of the herb and its products.     

Basic drug analysis by strong cation-exchange liquid chromatography-tandem mass spectrometry: simultaneous analysis of amisulpride, and of metamfetamine and amfetamine in serum/plasma

In the HPLC of basic drugs and metabolites, good efficiency and peak shape can often be attained using strong cation‐exchange packings with isocratic 100% methanol eluents containing an ionic modifier at an appropriate pH* and ionic strength. Solvent extracts can be analysed directly, and use of ammonium acetate as modifier facilitates the use of atmospheric pressure chemical ionization (APCI)–tandem mass spectrometry, selected reaction monitoring mode. For the analysis of amisulpride and of metamfetamine/amfetamine in plasma (200 µL) after single oral doses in man, a column packed with Waters Spherisorb S5SCX (5 µm average particle size, 100 × 2.1 mm i.d.) was used with methanolic ammonium acetate (40 mmol/L, pH* 6.0, flow rate 0.5 mL/min) as eluent (35°C). Deuterated internal standards were used for each analyte. Detection was by positive‐mode APCI. Responses for all analytes were linear over the calibration ranges. Intra‐assay precision (RSD) was 2–18%, and inter‐assay precision was 2–12%. The limit of detection was 0.5 µg/L for all analytes. No significant matrix effects or isobaric interferences were noted. The total analysis time was 7 min. Similar methodology can be applied to a wide range of basic analytes using MS/MS detection. Copyright © 2010 John Wiley & Sons, Ltd.     

Development of a novel monolith frit-based solid-phase microextraction method for determination of hexanal and heptanal in human serum samples

In this paper, a polypropylene frit with porous network structure and high area-to-thickness ratio (4.8 mm diameter, 1.6 mm thickness, 20 mm pore size) was utilized as a mould of monolith. Poly(methacrylic acid-ethlyene glycol dimethacrylate) (MAA-EGDMA) monolith was in situ synthesized in the micro-channel of frit by photopolymerization. A monolith frit-based solid-phase microextraction method (SPME) was developed for the determination of hexanal and heptanal in serum samples by combining with high-performance liquid chromatography. 2,4-Dinitrophenylhydrazine (DNPH) as the derivatizing reagent was absorbed on a monolith frit, then its derivatization reaction with aldehydes and the absorption of formed hydrazones on the monolith disk occurred simultaneously. The condition parameters for polymerization, derivatization and extraction were optimized systematically. Under the optimum conditions, rigid structure, low back-pressure and high column capacity were achieved for the monolith frit. The limits of detection for hexanal and heptanal were 1.86 and 1.38 nmol/L, respectively. The inter- and intra-day relative standard deviations were less than 7.7% (n = 6). This method was applied successfully to aldehydes analysis in human serum samples. The method possesses advantages such as simplicity, efficiency, low cost and good biocompatibility. It provides an alternative approach for quantification of aldehydes in complex biological samples.     

Screening for pesticide residues in oil seeds using solid-phase dispersion extraction and comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry

In this paper, we describe the development of an oil-absorbing matrix solid-phase dispersion extraction with comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry suitable for screening of 68 pesticide residues (PRs) in peanut, soybean, rape seed, sesame, and sunflower seed. The 68 PRs include 27 kinds of organophosphorus, 23 organic chlorines, 11 synthetic pyrethroids, and 7 carbamates. Heptachlor epoxide was used as the internal standard. Aminopropyl silica was chosen as the dispersion sorbent of the oil-absorbing matrix solid-phase dispersion extraction and was applied to capture hydrophobic components from high oil samples. A 35-min orthogonal separation was performed by using comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry with a nonpolar-polar column set. Identification of 68 PRs in the extract was finished by using the time-of-flight mass spectrometry in the assistance of an automated peak-find and spectral deconvolution software. A screening based on control design was introduced and explained. This screening method considerably reduced the cost for the quantitative and confirmatory analyses. The quality of present screening method was evaluated by the Document No. SANCO/10684/2009. The false positive rate and false negative rate provide a useful tool for the evaluation of screening performance.     

The adaptive buffered force QM/MM method in the CP2K and AMBER software packages

The implementation and validation of the adaptive buffered force (AdBF) quantum‐mechanics/molecular‐mechanics (QM/MM) method in two popular packages, CP2K and AMBER are presented. The implementations build on the existing QM/MM functionality in each code, extending it to allow for redefinition of the QM and MM regions during the simulation and reducing QM‐MM interface errors by discarding forces near the boundary according to the buffered force‐mixing approach. New adaptive thermostats, needed by force‐mixing methods, are also implemented. Different variants of the method are benchmarked by simulating the structure of bulk water, water autoprotolysis in the presence of zinc and dimethyl‐phosphate hydrolysis using various semiempirical Hamiltonians and density functional theory as the QM model. It is shown that with suitable parameters, based on force convergence tests, the AdBF QM/MM scheme can provide an accurate approximation of the structure in the dynamical QM region matching the corresponding fully QM simulations, as well as reproducing the correct energetics in all cases. Adaptive unbuffered force‐mixing and adaptive conventional QM/MM methods also provide reasonable results for some systems, but are more likely to suffer from instabilities and inaccuracies. © 2015 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc.     

Determination of pharmaceuticals in wastewaters using solid-phase extraction-liquid chromatography-tandem mass spectrometry

Four different commercial sorbents for solid-phase extraction have been evaluated for the extraction of a group of acidic pharmaceuticals in terms of selectivity and capacity: Oasis hydrophilic-lipophilic balance (HLB), Oasis MAX (strong anion exchange), Oasis WAX (weak anion exchange) and a commercial available molecularly imprinted polymer specific for non-steroidal anti-inflammatory drugs. Among the sorbents studied, molecularly imprinted polymer proved to be very effective in the reduction of matrix interferences and the selective extraction of acidic pharmaceuticals, such as salicylic acid, ibuprofen, fenoprofen, diclofenac and naproxen, among others, from effluent wastewater samples. Moreover, molecularly imprinted solid-phase extraction protocol was applied to liquid chromatography coupled to tandem mass spectrometry (MS/MS) with the purpose of evaluating the clean-up effect on ion suppression/enhancement when the complexity of the samples increases and a reduction of this effect was observed. Molecularly imprinted solid-phase extraction followed by liquid chromatography coupled to ultraviolet detection and liquid chromatography coupled to tandem mass spectrometry validation methodologies with effluent wastewaters were developed, obtaining recoveries between 70 and 85% and limits of detection at low levels of μg/L (0.15-1 μg/L) and ng/L (0.5-2 ng/L), respectively. The final application of molecularly imprinted solid-phase extraction and liquid chromatography coupled to MS/MS detection showed the presence of acidic pharmaceuticals studied in this work in effluent wastewaters (相似文献   

Qualitative and quantitative analysis of the chemical constituents in Mahuang‐Fuzi‐Xixin decoction based on high performance liquid chromatography combined with time‐of‐flight mass spectrometry and triple quadrupole mass spectrometers

High‐performance liquid chromatography coupled with time‐of‐flight mass spectrometry (HPLC‐TOF/MS) and high‐performance liquid chromatography–triple quadrupole mass spectrometry (HPLC‐QQQ/MS/MS) were utilized to clarify the chemical constituents of Mahuang‐Fuzi‐Xixin Decoction. There are 52 compounds, including alkaloids, amino acids and organic acids were identified or tentatively characterized by their characteristic high resolution mass data by HPLC‐QQQ/MS/MS. In the subsequent quantitative analysis, 10 constituents, including methyl ephedrine, aconine, songrine, fuziline, neoline, talatisamine, chasmanine, benzoylmesaconine, benzoylaconine and benzoylhypaconine were simultaneously determined by HPLC‐QQQ/MS/MS with multiple reaction monitoring mode. Satisfactory linearity was achieved with wide linear range and fine determination coefficient (r > 0.9992). The relative standard deviations (RSD) of inter‐ and intra‐day precisions were <3%. This method was also validated by repeatability, stability and recovery with RSD <3% respectively. A highly sensitive and efficient method was established for chemical constituents studying, including identification and quantification of Mahuang‐Fuzi‐Xixin decoction.     

Simultaneous determination of phenolic acids and flavonoids in rice using solid-phase extraction and RP-HPLC with photodiode array detection

An analytical method based on an optimized solid-phase extraction procedure and followed by high-performance liquid chromatography (HPLC) separation with diode array detection was developed and validated for the simultaneous determination of phenolic acids (gallic, protocatechuic, 4-hydroxy-benzoic, vanillic, caffeic, syringic, p-coumaric, ferulic, sinapic, and cinnamic acids), flavanols (catechin and epicatechin), flavonols (myricetin, quercetin, kaempferol, quercetin-3-O-glucoside, hyperoside, and rutin), flavones (luteolin and apigenin) and flavanones (naringenin and hesperidin) in rice flour (Oryza sativa L.). Chromatographic separation was carried out on a PerfectSil Target ODS-3 (250 mm × 4.6 mm, 3 μm) column at temperature 25°C using a mobile phase, consisting of 0.5% (v/v) acetic acid in water, methanol, and acetonitrile at a flow rate 1 mL min(-1) , under gradient elution conditions. Application of optimum extraction conditions, elaborated on both Lichrolut C(18) and Oasis HLB cartridges, have led to extraction of phenolic acids and flavonoids from rice flour with mean recoveries 84.3-113.0%. The developed method was validated in terms of linearity, accuracy, precision, stability, and sensitivity. Repeatability (n = 5) and inter-day precision (n = 4) revealed relative standard deviation (RSD) <13%. The optimized method was successfully applied to the analysis of phenolic acids and flavonoids in pigmented (red and black rice) and non-pigmented rice (brown rice) samples.     

Synthesis and cytotoxic activity of silacycloalkyl‐substituted heterocyclic aldehydes and their thiosemicarbazones

A series of 5‐[1‐methylsilacyclo‐pentyl/‐hexyl]‐2‐furfural, 5‐[1‐methylsilacyclo‐pentyl/‐hexyl]‐2‐thiophene carbaldehyde and 1,1‐bis(5‐formyl‐2‐furyl)silacyclo‐pentane/‐hexane and their thiosemicarbazones has been synthesized and subjected to antitumour assay. The effects of the substituents and the heterocycle were examined to establish structure–activity relationships. Thiosemicarbazones of 5‐(1‐methylsilacyclohexyl)furfural and 5‐(1‐methylsilacyclopentyl)furfural were very active (1.0–4.0 µg ml^?1) in vitro against human fibrosarcoma HT‐1080 and mouse hepatoma MG‐22A cells. At the same time, they were less toxic for normal fibroblasts 3T3. All compounds synthesized exhibited low or moderate toxicity (LD₅₀ 152–1904 mg kg^?1). Copyright © 2005 John Wiley & Sons, Ltd.     

New designer drug 4-iodo-2,5-dimethoxy-beta-phenethylamine (2C-I): studies on its metabolism and toxicological detection in rat urine using gas chromatographic/mass spectrometric and capillary electrophoretic/mass spectrometric techniques

Studies are described on the metabolism and the toxicological analysis of the phenethylamine-derived designer drug 4-iodo-2,5-dimethoxy-beta-phenethylamine (2C-I) in rat urine using gas chromatographic/mass spectrometric (GC/MS) techniques, and for a particular question, using capillary electrophoretic/mass spectrometric (CE/MS) techniques. The identified metabolites indicated that 2C-I was metabolized on the one hand by O-demethylation in position 2 and 5, respectively, followed either by N-acetylation or by deamination with subsequent oxidation to the corresponding acid or reduction to the corresponding alcohol, respectively. The latter metabolite was hydroxylated in beta-position and further oxidized to the corresponding oxo metabolite. On the other hand, 2C-I was metabolized by deamination with subsequent oxidation to the corresponding acid or reduction to the corresponding alcohol, respectively. 2C-I and most of its metabolites were partially excreted in conjugated form. The authors' systematic toxicological analysis (STA) procedure using full-scan GC/MS after acid hydrolysis, liquid-liquid extraction and microwave-assisted acetylation allowed the detection of an intake of a dose of 2C-I in rat urine that corresponds to a common drug users' dose. Assuming similar metabolism, the described STA procedure should be suitable for proof of an intake of 2C-I in human urine.     

Liquid chromatography/quadrupole time‐of‐flight mass spectrometry in combination with online hydrogen/deuterium exchange technique for structural elucidation of phase I metabolites of iso‐phenylcyclopentylamine in rat bile

MS/MS experiment and accurate mass measurement are powerful tools in metabolite identification. However, sometimes these data do not provide enough information to assign an unambiguous structure to a metabolite. In combination with MS techniques, hydrogen/deuterium (H/D) exchange can provide additional information for structural elucidation by determination of the number of exchangeable hydrogen atoms in a structure. In this study, the principal phase I metabolites of iso‐phenylcyclopentylamine in rat bile were identified by high‐performance liquid chromatography with electrospray ionization quadrupole time‐of‐flight mass spectrometry (ESI‐Q‐TOF‐MS). Since N‐oxidation may occur because of the existence of the primary amino group in the structure, it was difficult to differentiate the hydroxylated metabolites from N‐oxides by ESI‐Q‐TOF‐MS alone. Therefore, online H/D exchange technique was applied to solve this problem. Finally, 25 phase I metabolites were detected and structurally described, in which 11 were confirmed to be N‐oxides. This study demonstrated the effectiveness of high‐resolution mass spectrometry in combination with an online H/D exchange technique in rapid identification of drug metabolites, especially in discriminating hydroxylated metabolites from N‐oxides. Copyright © 2014 John Wiley & Sons, Ltd.