Performance Liquid Chromatography-triple Quadrupole Mass Research Articles

Targeted metabolomics analysis reveals the association between maternal folic acid supplementation and fatty acids and amino acids profiles in rat pups

Maternal diet during pregnancy can influence offspring's health by affecting development and metabolism. This study aimed to analyze the influence of maternal folic acid (FA) supplementation on the metabolism of rat pups using targeted metabolomics. Twenty female rats were randomly assigned to a FA supplementation (FAS group, n = 10) or control group (n = 10), which were fed AIN93G diet with 2 or 10 mg/kg FA, respectively. We then measured amino acids and their derivatives, biogenic amines, and fatty acids in the female rats and their pups by ultra-high performance liquid chromatography-triple quadrupole mass spectrometry (UHPLC/MS-MS) and gas chromatography–mass spectrometry (GC/MS-MS). In maternal rats, the significant changes of three metabolites (proline, γ-aminobutyric acid and esterified octadecatetraenoic acid, P < 0.05) were observed in FAS group. For the rat pups, FAS pups had significantly lower homocysteine and higher FA levels than control pups. The lower levels of amino acids (leucine, isoleucine, serine, proline) were obtained in FAS pups. Furthermore, there were the decreased esterified fatty acids (arachidonic acid, eicosapentaenoic acid, and docosatetraenoic acid) and free fatty acids (oleic acid, linoleic acid, γ-linolenic acid, octadecatetraenoic acid, arachidonic acid, eicosapentaenoic acid and selacholeic acid) in FAS pups. Metabolic changes in the FAS pups were characterized by changes in fatty acids and amino acids. These results suggested that FA supplementation during pregnancy influenced amino acids and fatty acids metabolism in rat pups. This study provides new insights into the regulation of amino acids and fatty acids metabolism during early life.

Perturbations in amino acids and metabolic pathways in osteoarthritis patients determined by targeted metabolomics analysis

Osteoarthritis (OA) is a degenerative synovial joint disease affecting people worldwide. However, the exact pathogenesis of OA remains unclear. Metabolomics analysis was performed to obtain insight into possible pathogenic mechanisms and diagnostic biomarkers of OA. Ultra-high performance liquid chromatography-triple quadrupole mass spectrometry (UPLC-TQ-MS), followed by multivariate statistical analysis, was used to determine the serum amino acid profiles of 32 OA patients and 35 healthy controls. Variable importance for project values and Student's t-test were used to determine the metabolic abnormalities in OA. Another 30 OA patients were used as independent samples to validate the alterations in amino acids. MetaboAnalyst was used to identify the key amino acid pathways and construct metabolic networks describing their relationships. A total of 25 amino acids and four biogenic amines were detected by UPLC-TQ-MS. Differences in amino acid profiles were found between the healthy controls and OA patients. Alanine, γ-aminobutyric acid and 4-hydroxy-l-proline were important biomarkers distinguishing OA patients from healthy controls. The metabolic pathways with the most significant effects were involved in metabolism of alanine, aspartate, glutamate, arginine and proline. The results of this study improve understanding of the amino acid metabolic abnormalities and pathogenic mechanisms of OA at the molecular level. The metabolic perturbations may be important for the diagnosis and prevention of OA.

Detection of prohibited substances in equine hair by ultra-high performance liquid chromatography-triple quadrupole mass spectrometry - application to doping control samples.

The detection of drugs in human hair samples has been performed by laboratories around the world for many years and the matrix is popular in disciplines, such as workplace drug testing. To date, however, hair has not become a routinely utilised matrix in sports drug detection. The analysis of hair samples offers several potential advantages to doping control laboratories, not least of which are the greatly extended detection window and the ease of sample collection and storage. This article describes the development, validation, and utilisation of a sensitive ultra-high performance liquid chromatography-triple quadrupole mass spectrometry (UHPLC-MS/MS) method for the detection of 50 compounds. This provides significantly improved coverage for those analytes which would be of particular interest if detected in hair, such as anabolic steroid esters and selective androgen receptor modulators (SARMs). Qualitative validation of the method resulted in estimated limits of detection as low as 0.1pg/mg for the majority of compounds, with all being detected at 2pg/mg or below. The suitability of the method for the detection of prohibited substances in incurred material was demonstrated by the successful detection of several compounds, such as stanozolol, boldenone undecylenate, clenbuterol, and GW-501516, in genuine equine hair samples. Estimated concentrations of the detected substances ranged from 0.27 to 8.6pg/mg. The method has been shown to be fit-for-purpose for routine screening of equine hair samples by the analysis of over 400 genuine hair samples.

Fast and quantitative determination of saxitoxin and neosaxitoxin in urine by ultra performance liquid chromatography-triple quadrupole mass spectrometry based on the cleanup of solid phase extraction with hydrophilic interaction mechanism.

Saxitoxin (STX) and neosaxitoxin (NEO) are water-soluble toxins and their cleanup in bio-matrix is a hot topic but difficult problem. A fast and quantitative determination method for STX and NEO in urine was developed using ultra performance liquid chromatography-triple quadrupole mass spectrometry (LC-MS/MS) based on the cleanup of solid phase extraction (SPE) with hydrophilic interaction (HILIC) mechanism. Acetonitrile/methanol/water mixture was used to extract the toxins in urine. Polyamide (PA) was used as HILIC SPE material to clean the toxins in sample matrix. The limits of detection were 0.2ngmL-1 for STX and 1ngmL-1 for NEO in urine. The linear ranges were 0.5ngmL-1-99.2ngmL-1 with the correlation coefficient of r=0.9992 for STX and 2.1ngmL-1-207ngmL-1 with r=0.997 for NEO in urine matrix. The recoveries at three spiking levels were 81.5%-117% with the relative standard deviations (RSDs) of 5.4%-8.5% for STX and 89.0%-118% with the RSDs of 6.7%-9.1% for NEO. STX was found in all the 6 patients' urines while NEO was only found in one sample from an intoxication case.

Accurate Determination of Isotopic Abundance of Intracellular Metabolites of Saccharopolysporaerythraea Based on Ultra Performance Liquid Chromatography-Triple Quadrupole Mass Spectrometry

Abstract A method was established for measuring 13C isotopic abundance of intracellular metabolites of Saccharopolysporaerythraea by ultra-high performance liquid chromatography (UPLC)-triple quadrupole mass spectrometry. Under the optimized chromatographic conditions of UPLC, and the appropriate and unique tube lens voltage, collision energy and ion pair, one-to-one method, one-to-many method and SIM method were established for measuring 13C isotopic abundance based on the length of the parent and daughter ions carbon chains and whether the daughter ions contain 13C atoms. The three methods were then applied to measure naturally labeled intracellular metabolite standards and 13C labeled samples. According to the gap between the experimental value and the theoretical value, the best method was found for each metabolite of different characteristics. The results showed that one-to-one method was the most effective for measuring the metabolites of daughter ions not containing 13C atoms represented by sugar phosphates, one-to-many method was the best for measuring the metabolites of both parent and daughter ions containing 13C short carbon chains represented by carboxylic acids, SIM method could played a role in measuring the metabolites of both parent and daughter ions containing 13C long carbon chains represented by coenzyme A. These methods had a good measurement precision and could be applied to the measurement of Saccharopolysporaerythraea intracellular metabolites, which would contribute to consequent study of the metabolic mechanism and the efficient expression of erythromycin.

Laser microdissection hyphenated with high performance gel permeation chromatography-charged aerosol detector and ultra performance liquid chromatography-triple quadrupole mass spectrometry for histochemical analysis of polysaccharides in herbal medicine: Ginseng, a case study

This study establishes a new combinatorial approach for histochemical analysis of polysaccharides in herbal medicines using laser microdissection followed by high performance gel permeation chromatography coupled with charged aerosol detector and ultra-performance liquid chromatography hyphenated with triple quadrupole mass spectrometry. Ginseng was employed as a study model. Tissue-specific qualitative and quantitative characterization of ginseng polysaccharides was performed by determining their molar masses and monosaccharide compositions in three macro-dissected parts (rhizome, main and branched roots) and five micro-dissected tissues (cork, cortex, xylem, phloem and resin canal). The results showed that ginseng “flesh” (xylem, phloem and resin canal) contained more polysaccharides with larger molecular weights and higher ratios of glucose residue, whereas ginseng “skin” (cork and cortex) had fewer polysaccharides with smaller molecular weights and higher ratios of non-glucose constituents (e.g. galacturonic acid, galactose, arabinose and rhamnose). These findings suggested that the polysaccharides of the “flesh” were predominantly starch-like glucans, while those of the “skin” were of a higher proportion of acidic pectins. The revealed histologic distribution and accumulation pattern of ginseng polysaccharides contributes to the scientific understanding of ginseng regarding the biosynthesis and transportation of polysaccharides, medicinal quality evaluation as well as empirical clinical application.

Analysis of trace microcystins in vegetables using matrix solid-phase dispersion followed by high performance liquid chromatography triple-quadrupole mass spectrometry detection

A selective and sensitive method for the simultaneous determination of five common microcystins (MC-LR, -RR, -YR, -LW, -LF) in various vegetables was established using Matrix Solid-Phase Dispersion (MSPD) followed by high performance liquid chromatography-mass spectrometry detection. To optimize the pretreatment procedure for extracting the microcystins from three vegetable matrices (tomato, cucumber and spinacia, which represented different colors), Box-Behnken design was employed to optimize the main factors affecting the extraction efficiency, including sample/dispersant mass ratio, as well as the proportion mixture dispersant and the volumes of solvent. Based on the optimum conditions, the intra-day and inter-day variability for each microcystins in all vegetable samples were less than 8.6%, with the recoveries ranging from 71.9% to 96.5%. The limits of detection and quantitation of the method were 13.0μg/kg (dw) and 43.0μg/kg (dw), respectively. The established method was successfully applied to the analysis of MCs in vegetable samples which were collected by Lake Taihu. The procedure promising to be relative small sample size and short pretreatment time for the assay that can be used for monitoring MCs concentrations in vegetables.

Simultaneous rapid determination of 12 microcystins and one nodularin in water by direct injection-ultra performance liquid chromatography-triple quadrupole mass spectrometry

A rapid method was developed for the simultaneous determination of 12 microcystins (MCs) and one nodularin (NOD) in water by direct injection-ultra performance liquid chromatography-triple quadrupole mass spectrometry (UPLC-MS/MS). The water samples were first diluted with equal volume of methanol, and then filtered through polyether sulfone (PES) syringe filter. The filtrates were directly injected into the UPLC system. The separation of the analytes was carried out on an ACQUITY UPLC BEH 300 C18 column (100 mm×2.1 mm, 1.7 μm) with gradient elution using mobile phases of acetonitrile containing 0.1% (v/v) formic acid and 0.2% (v/v) formic acid aqueous solution. The 12 microcystins and one nodularin were detected by positive electrospray ionization in the multiple reaction monitoring (MRM) mode, and quantified by standard solvent external standard method. The limits of detection were 0.03-0.1 μg/L and the limits of quantification were 0.1-0.3 μg/L. The recoveries were in the range of 79.5%-123% with the relative standard deviations ranging from 1.0% to 20% (n=6). The method is simple, sensitive and accurate, and has been successfully applied to the detection of the 13 kinds of algae toxins in water.

Determination of seven fluorescent whitening agents in flour by high performance liquid chromatography-triple quadrupole mass spectrometry

Determination of seven fluorescent whitening agents in flour by high performance liquid chromatography-triple quadrupole mass spectrometry

Rapid determination of benzo[a]pyrene in foods by ultra performance liquid chromatography-triple quadrupole mass spectrometry with atmospheric pressure chemical ionization

A method for the determination of benzo[a]pyrene in foods was developed by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) based on isotope dilution and molecularly imprinted solid-phase extraction (MIP-SPE). The target analyte in samples was extracted with n-hexane after spiked with benzo[a]pyrene-d12, and purified using MIP-SPE to eliminate most of the coextracts. The separation of benzo[a]pyrene was carried out on an XBridge BEH C18 column with gradient elution of methanol and water. An atmospheric pressure chemical ionization (APCI) interface was used as the ion source and the analysis was performed in the multiple reaction monitoring (MRM) mode. Benzo[a]pyrene levels in the range of 0.07-50 μg/kg were measured accurately by this method, and the limit of quantification (LOQ) was 0.07 μg/kg. The average recoveries were between 86% and 104% with the relative standard deviations within 2.3%-14%. The method was sensitive and accurate, and it has been successfully applied to the measurement of benzo[a]pyrene in food samples.

Determination of 34 illegally adulterated weight loss compounds in foods by ultra high performance liquid chromatography- triple quadrupole mass spectrometry

An analytical method was developed for the determination of 34 illegally adulterated weight loss compounds in foods and dietary supplements by ultra high performance liquid chromatography-triple quadrupole mass spectrometry (UHPLC-MS/MS). A Waters CORTECS T3 column (100 mm×2.1 mm, 2.7 μm) was used with 0.1% (v/v) formic acid aqueous solution-acetonitrile containing 0.1% (v/v) formic acid as mobile phases by gradient elution. The compounds were detected by electrospray ion source in positive or negative mode with multiple reaction monitoring (MRM) mode. The calibration curves showed good linearity in the range of 0.5-10 μg/L for 29 compounds such as sibutramine, and in the range of 2.5-50 μg/L for five compounds such as chlorothiazide. The correlation coefficients (r) of the standard calibration curves for the 34 analytes were all greater than 0.99. The recoveries of the 29 compounds at spiked levels of 5, 10 and 20 μg/kg were in the range of 49.2%-136.2%, and the RSDs were 0.7%-15.0% (n=6). The recoveries of the five compounds at spiked levels of 25, 50 and 100 μg/kg were in the range of 51.5%-130.9%, and the RSDs were 0.8%-14.0% (n=6). The limits of detection (LODs) and limits of quantification (LOQs) were 5 μg/kg and 10 μg/kg for the 29 compounds, 25 μg/kg and 50 μg/kg for the five compounds, respectively. The method was successfully applied to the analysis of actual samples, and 12 compounds were checked out, which combated the illegal adulteration behavior effectively.

High-sensitivity detection of biogenic amines with multiple reaction monitoring in fish based on benzoyl chloride derivatization

In this study an efficient and sensitive method for biogenic amines detection was established by combining rapid extraction and derivatization with multiple reaction monitoring (MRM) based on ultra high performance liquid chromatography-triple quadrupole mass spectrometry. Bead-beating disruption and extraction using 5-sulfosalicylic acid not only improved the extraction efficiency but also was environmentally friendly. Benzoyl chloride derivatization could obtain stable biogenic amine derivatives with a shorter reaction time. By combining with MRM detection mode, higher detection sensitivity for biogenic amines could be achieved. The method showed a good linearity with linear range of 3–4 orders of magnitude and regression coefficients ranging from 0.9966 to 0.9999. The limit of detection and limit of quantitation could even reach lower pg/mL level. Satisfactory recovery was obtained from 74.9% to 119.3%. And the derivatives were stable within 48h at 4°C. The method established was used to determine content of biogenic amines in different fishes at different storage conditions. The results indicated that this method was suitable for analysis of biogenic amines.

13C-assisted Ultra-High Performance Liquid Chromatography-Triple Quadrupole Mass Spectrometry Method for Precise Determination of Intracellular Metabolites in Pichia pastoris

Abstract The yeast Pichia pastoris is an effective host for recombinant protein production and the recombinant protein production level is tightly related to the concentrations of intracellular metabolites. The intracellular metabolites have the features of wide range of types, distinct variation in physical and chemical properties, rapid turning-over and low concentration, so it is difficult to quantify their concentrations precisely. In this study, we tried to make it possible by combining ultra-high performance liquid chromatography-triple quadrupole mass spectrometry method and 13 C isotope labeling techniques. 64 metabolites including organic acids, sugar phosphate, nucleoside substance, amino acid were successfully separated by UPLC with three kinds of chromatographic column. The appropriate and unique ion pairs and collision voltages were found after the mass spectrometry condition optimization. By using the U 13 C metabolites as internal standards collected from the cells growing on U 13 C-glucose as sole carbon source, the standard curves of 53 metabolites was established. The results showed that this method had a high accuracy. The correlation coefficients were above 0.99. The method also had a good reproducibility, and the influence of experimental and equipment operating condition was very small. Reliable and accurate determination of the concentrations of intracellular metabolites in Pichia pastoris was obtained. The works lays the foundation for comprehensive regulation mechanism research and efficient recombinant protein production in Pichia pastoris .

Determination of ginkgolic acids in the ginkgo biloba extract and its preparations by ultra high performance liquid chromatography-triple quadrupole mass spectrometry

An analytical method was developed for the determination of ginkgolic acids in ginkgo biloba extract and its preparations by ultra high performance liquid chromatography-triple quadrupole mass spectrometry. A chromatographic column, Agilent Poroshell 120 EC-C18 (50 mm x 3. 0 mm, 2.7 µm), was used with methanol-l% acetic acid (90 :10, v/v) as the mobile phase. The ginkgo acids were detected by electrospray ionization mass spectrometry in negative mode with multiple reaction monitoring (MRM) mode. Ginkgo acids C13:0, C15:1 and C17:1 possessed good linear correlations in the mass concentration range from 2 to 200 µg/L, with the correlation coefficients more than 0. 999. The mean recoveries at the spiked levels of 5, 20 and 100 µg/L were in the range of 86. 3%-114. 3%, and the RSDs were 0. 5%-13. 6%. The limits of detection and quantification were 0. 003-0. 08 µg/g and 0. 01-0. 19 µg/g, respectively. The method was successfully applied to the analysis of actual samples.

A New Fluorinated Surfactant Contaminant in Biota: Perfluorobutane Sulfonamide in Several Fish Species.

Environmental contamination and regulation of longer-chain perfluoroalkyl substances (PFASs) such as perfluorooctanesulfonate (PFOS) has given rise to the increased use of shorter-chain PFASs as alternatives in new products, although confirmation of their presence in the environment remains limited. In this study, the PFAS alternative, perfluoro-1-butane-sulfonamide (FBSA), was identified for the first time in biota in homogenate samples of fish by liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-Q-ToF-MS) and quantified by ultra high performance liquid chromatography-triple quadrupole mass spectrometry (UHPLC-QQQ-MS/MS). In one flounder (Platichthys flesus) muscle sample from the Western Scheldt, The Netherlands, FBSA concentration was at 80.12 ng/g wet weight (w.w.) and was exceeded only by PFOS. FBSA was also detected in 32 out of 33 samples of freshwater fish collected (2009-2010) from water bodies across Canada. In lake trout (Salvelinus namaycush) from northern Canada (e.g., Lake Kusawa (Yukon Territory), Great Bear Lake (Northwest Territories and in the Arctic), and Lake Athabasca (northern Alberta)), the concentrations of FBSA ranged from below method detection limit (<0.01 ng/g w.w) to 0.44 ng/g w.w. and were much lower than those reported for lake trout from the more urbanized and industrialized Laurentian Great Lakes sites (3.17 ± 1.53 ng/g w.w.). In three species of fish purchased from a supermarket in Ottawa (ON, Canada), FBSA concentrations were the lowest of all fish and ranged from < MLOD to 0.29 ng/g w.w. and 0.03 to 0.76 ng/g w.w. in muscle and liver, respectively. FBSA is a bioaccumulative contaminant in fish in Canada and possibly in The Netherlands. It is likely sourced from new alternative perfluorobutane-based products, as well as other shorter chain perfluoroalkyl-based products.

The roles of carboxylesterase and CYP isozymes on the in vitro metabolism of T-2 toxin.

BackgroundT-2 toxin poses a great threat to human health because it has the highest toxicity of the currently known trichothecene mycotoxins. To understand the in vivo toxicity and transformation mechanism of T-2 toxin, we investigated the role of one kind of principal phase I drug-metabolizing enzymes (cytochrome P450 [CYP450] enzymes) on the metabolism of T-2 toxin, which are crucial to the metabolism of endogenous substances and xenobiotics. We also investigated carboxylesterase, which also plays an important role in the metabolism of toxic substances.MethodsA chemical inhibition method and a recombinant method were employed to investigate the metabolism of the T-2 toxin by the CYP450 enzymes, and a chemical inhibition method was used to study carboxylesterase metabolism. Samples incubated with human liver microsomes were analyzed by high performance liquid chromatography-triple quadrupole mass spectrometry (HPLC- QqQ MS) after a simple pretreatment.ResultsIn the presence of a carboxylesterase inhibitor, only 20 % T-2 toxin was metabolized. When CYP enzyme inhibitors and a carboxylesterase inhibitor were both present, only 3 % of the T-2 toxin was metabolized. The contributions of the CYP450 enzyme family to T-2 toxin metabolism followed the descending order CYP3A4, CYP2E1, CYP1A2, CYP2B6 or CYP2D6 or CYP2C19.ConclusionCarboxylesterase and CYP450 enzymes are of great importance in T-2 toxin metabolism, in which carboxylesterase is predominant and CYP450 has a subordinate role. CYP3A4 is the principal member of the CYP450 enzyme family responsible for T-2 toxin metabolism. The primary metabolite produced by carboxylesterase is HT-2, and the main metabolite produced by CYP 3A4 is 3′-OH T-2. The different metabolites show different toxicities. Our results will provide useful data concerning the toxic mechanism, the safety evaluation, and the health risk assessment of T-2 toxin.

Targeted metabolomic analysis reveals the association between the postprandial change in palmitic acid, branched-chain amino acids and insulin resistance in young obese subjects

Obesity is the result of a positive energy balance and often leads to difficulties in maintaining normal postprandial metabolism. The changes in postprandial metabolites after an oral glucose tolerance test (OGTT) in young obese Chinese men are unclear. In this work, the aim is to investigate the complex metabolic alterations in obesity provoked by an OGTT using targeted metabolomics. We used gas chromatography–mass spectrometry and ultra high performance liquid chromatography–triple quadrupole mass spectrometry to analyze serum fatty acids, amino acids and biogenic amines profiles from 15 control and 15 obese subjects at 0, 30, 60, 90 and 120min during an OGTT. Metabolite profiles from 30 obese subjects as independent samples were detected in order to validate the change of metabolites. There were the decreased levels of fatty acid, amino acids and biogenic amines after OGTT in obesity. At 120min, percent change of 20 metabolites in obesity has statistical significance when comparing with the controls. The obese parameters was positively associated with changes in arginine and histidine (P<0.05) and the postprandial change in palmitic acid (PA), branched-chain amino acids (BCAAs) and phenylalanine between 1 and 120min were positively associated with fasting insulin and HOMA-IR (all P<0.05) in the obese group. The postprandial metabolite of PA and BCAAs may play important role in the development and onset of insulin resistance in obesity. Our findings offer new insights in the complex physiological regulation of the metabolism during an OGTT in obesity.

Simultaneous determination of 22 typical pharmaceuticals and personal care products in environmental water using ultra performance liquid chromatography- triple quadrupole mass spectrometry

An analytical method for simultaneous determination of 22 typical pharmaceuticals and personal care products (PPCPs) in environmental water samples was developed by ultra performance liquid chromatography-triple quadrupole mass spectrometry (UPLC-MS/MS). An Oasis HLB solid phase extraction cartridge, methanol as washing solution, water containing 0. 1% formic acid-methanol (7:3, v/v) as the mobile phases were selected for sample pretreatment and chromatographic separation. Based on the optimized sample pretreatment procedures and separation condition, the target recoveries ranged from 73% to 125% in water with the relative standard deviations ( RSDs) from 8.8% to 17.5%, and the linear ranges were from 2 to 2 000 µg/L with correlation coefficients (R2) not less than 0.997. The method can be applied to simultaneous determination of the 22 typical PPCPs in environmental water samples because of its low detection limits and high recoveries. It can provide support and help for the related research on water environmental risk assessment and control of the micro-organic pollutants.

Multi-residue method for the analysis of pharmaceuticals and some of their metabolites in bivalves

A fast, simple and robust method has been developed for the simultaneous determination of 23 pharmaceuticals (including some major metabolites) in bivalve mollusks. The analytes belong to eight different therapeutic groups: antibiotics, psychiatric drugs, analgesics/anti-inflammatories, tranquilizer, calcium channel blockers, diuretic, and prostatic hyperplasia. The method is based on pressurized liquid extraction (PLE) followed by solid phase extraction clean-up (SPE), and ultra performance liquid chromatography–triple quadrupole mass spectrometry (UHPL–MS/MS) for the identification and quantification of the target analytes. It has been developed and validated in three different species of bivalves: Crassostrea gigas (Pacific oyster), Mytilus galloprovincialis (Mediterranean mussel), and Chamelea gallina (striped venus clam). The majority of the compounds were extracted with a recovery between 40 and 115%. The developed analytical method allowed the determination of the compounds in the lower ng/g concentration levels. The relative standard deviation was under 12% for the intra-day and 20% inter-day analyses, respectively. Finally, the method was applied to oyster, clam and mussel samples collected from the Ebro delta, Spain. The most ubiquitous compounds detected were the psychiatric drug venlanfaxine and the antibiotic azithromycin, with the highest concentrations found in mussel (2.7ng/g dw) and oyster (3.0ng/g dw), respectively. To the best of our knowledge, this is the first time that azithromycin has been reported in environmental samples of marine biota.

Determination of nine phthalate ester metabolites in human urine using ultra high performance liquid chromatography-tandem triple quadrupole mass spectrometry

A method was developed to determine trace concentrations of phthalate ester (PAE) metabolites in human urine by using ultra high performance liquid chromatography-triple quadrupole mass spectrometry. Aliquots (2 mL) of human urine samples were purified using strong anion-exchange solid-phase extraction after enzymatic deconjugation by glucuronidase for 2 h. The separation was performed on a Waters ACQUITY UPLC BEH Phenyl column (100 mm×2.1 mm, 1.7 μ m) with gradient elution by 0.1% (v/v) acetic acid in acetonitrile and 0.1% (v/v) acetic acid aqueous solution. The concentrations of nine PAE metabolites were determined under a multiple reaction monitoring mode by negative electrospray ionization. Eight of the determined metabolites showed good linearities in the range of 0.39-200 μ g/L, and the ninth metabolite showed linearity in the range of 1.17-600 μ g/L with correlation coefficients > 0.995. The limits of detection ranged from 0.06 to 0.85 μ g/L, and the limits of quantification ranged from 0.20 to 2.80 μ g/L. The recovery rates at all three spiked levels ranged from 84.1% to 122% with relative standard deviations between 4.5% and 14.3%. The intra-and inter-day precisions were not more than 10.1% and 9.3%, respectively. The matrix effect and stability were found to be favorable for analysis. This method was utilized for the determination of 50 human urine samples. The detection rates of monocyclohexyl phthalate (MCHP) and monobenzyl phthalate (MBZP) were 0 and 44.0%, and the detection rates of the other seven PAE metabolites was 100%. This method has the advantage of convenient operation and good accuracy and stability, and is suitable for the quantitative determination of the nine PAE metabolites in human urine.