Solid-phase Extraction Liquid Chromatography-mass Spectrometry Research Articles

International Comparison, Risk Assessment, and Prioritisation of 26 Endocrine Disrupting Compounds in Three European River Catchments in the UK, Ireland, and Spain.

Endocrine-disrupting compounds (EDCs) constitute a wide variety of chemistries with diverse properties that may/can pose risks to both humans and the environment. Herein, a total of 26 compounds, including steroids, flame retardants, and plasticizers, were monitored in three major and heavily urbanized river catchments: the R. Liffey (Ireland), the R. Thames (UK), and the R. Ter (Spain), by using a single solid-phase extraction liquid chromatography-mass spectrometry (SPE-LC-MS/MS) method. Occurrence and frequency rates were investigated across all locations over a 10-week period, with the highest concentration obtained for the flame retardant tris(2-chloroethyl) phosphate (TCEP) at 4767 ng∙L-1 in the R. Thames in Central London. Geographical variations were observed between sites and were partially explained using principal component analysis (PCA) and hierarchical cluster analysis (HCA). In particular, discrimination between the R. Ter and the R. Thames was observed based on the presence and concentration of flame retardants, benzotriazole, and steroids. Environmental risk assessment (ERA) across sites showed that caffeine, a chemical marker, and bisphenol A (BPA), a plasticizer, were classified as high-risk for the R. Liffey and R. Thames, based on relative risk quotients (rRQs), and that caffeine was classified as high-risk for the R. Ter, based on RQs. The total risks at each location, namely ΣRQriver, and ΣrRQriver, were: 361, 455, and 723 for the rivers Liffey, Thames, and Ter, respectively. Caffeine, as expected, was ubiquitous in all 3 urban areas, though with the highest RQ observed in the R. Ter. High contributions of BPA were also observed across the three matrices. Therefore, these two compounds should be prioritized independently of location. This study represents a comprehensive EDC monitoring comparison between different European cities based on a single analytical method, which allowed for a geographically independent ERA prioritization to be performed.

Lipidomic Profiling of Algae with Microarray MALDI-MS toward Ecotoxicological Monitoring of Herbicide Exposure.

Misuse of agrochemicals has a long-lasting negative impact on aquatic systems. Mismanagement of herbicides in agri-food sectors is often linked to a simultaneous decline in the health of downstream waterways. However, monitoring the herbicide levels in these areas is a laborious task, and modern analytical approaches, such as solid-phase extraction-liquid chromatography-mass spectrometry (SPE-LC-MS) and enzyme-linked immunosorbent assay, are low-throughput and require significant sample preparation. We report here the use of microchip technology in combination with matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) for the assessment of the ecotoxicological effect of agrochemicals on aquatic species at the single-cell level. This approach quantifies the fluctuations in lipid content in sentinel organisms and targets the microalga, Chlamydomonas reinhardtii (C. reinhardtii), as the model system. Specifically, we investigated the cytotoxicity of three herbicides (atrazine, clomazone, and norflurazon) on C. reinhardtii by analyzing the lipid component variation upon assorted herbicide exposure. Lipidomic profiling reveals a significantly altered lipid content at >EC50 in atrazine-exposed cells. The response for norflurazon showed similar trends but diminished in magnitude, while the result for clomazone was near muted. At lower herbicide concentrations, digalactosyldiacylglycerols showed a rapid decrease in abundance, while several other lipids displayed a moderate increase. The microchip-based MALDI technique demonstrates the ability to achieve lipidomic profiling of aquatic species exposed to different stressors, proving effective for high-throughput screening and single-cell analysis in ecotoxicity studies.

Determination of endocannabinoids and N-acylethanolamines in human hair with LC-MS/MS and their relation to symptoms of depression, burnout, and anxiety

The endocannabinoid system has been implicated in the dynamic regulation of the stress response, fear memory formation, and inflammatory processes. Endocannabinoids (eCBs) and N-acylethanolamines (NAEs) are primarily quantified from serum or cerebrospinal fluid representing acute measures, while no validated method for the quantification of long-term integrated eCBs and NAEs concentrations exists. We here present an online solid phase extraction-liquid chromatography-mass spectrometry method (LC-MS/MS) for quantification of long-term integrated eCBs and NAEs in human hair and examine their association with burnout, depression, and anxiety symptoms. Hair samples were washed with isopropanol and endocannabinoids were extracted from 7.5 mg hair by methanol incubation. A column switching strategy for online solid phase extraction (SPE) was applied, followed by mass spectrometer detection. eCBs and NAEs levels were determined in 207 hair samples from an ongoing longitudinal study and related to individual burnout, depression and anxiety symptoms. The limits of detection were between 0.06 and 6.0 pg mg−1, the recoveries of this method were between 87.2% and 114.2%. Hair AEA levels showed a negative correlation with burnout and anxiety symptoms. Participants with clinically relevant burnout and anxiety symptomatology exhibited lower hair AEA levels compared to those participants with low burnout and anxiety symptomatology, while for depressive symptomatology no association was identified. The presented LC-MS/MS method provides a highly specific analytical strategy for the detection of eCBs and NAEs concentrations in human hair and is thus likely to further shed light on the temporal dynamics of eCBs and NAEs secretion. The analysis of eCBs and NAEs in hair emerges as useful strategy in biopsychological research and as a valid and easily implementable method for the retrospective assessment of cumulative long-term eCBs and NAEs secretion.

Determination of thyroid hormones in human hair with online SPE LC–MS/MS: Analytical protocol and application in study of burnout

Thyroid hormones (THs) play a key role within the endocrine system. Incorporated biomarkers in hair can reflect endogenous excretion patterns over several months. We present an online solid phase extraction-liquid chromatography-mass spectrometry (online SPE-LC–MS/MS) method for quantification of THs in human hair and test it in the volunteers suffering from different severity of burnout symptom. THs were extracted from 7.5 mg hair by methanol incubation. Extracts were analyzed with LC–MS/MS in positive electrospray ionization mode. Burnout symptoms were assessed with the Maslach Burnout Inventory-General Survey (MBI-GS). THs levels were determined in 208 hair samples from adults and related to individual MBI-GS score. Intra- and inter-day coefficients of variance were between 3.1% and 10.2%. The recoveries of this method were between 88.5% and 102.1%. Hair T4 levels correlated significantly with total and free T4 in plasma. Participants with high degree of burnout had significantly higher hair T4 levels and lower T3/T4 ratio compared to those with no or moderate degree of burnout. A trend towards higher hair T3 levels was observed in subjects with high burnout score. Hair T4 levels showed a significant positive relationship with MBI-GS score, whereas no significant correlation emerged for hair T3 levels. The negative correlation between T3/T4 ratio and MBI-GS score was also significant. We have developed an online SPE-LC–MS/MS method for measurement of THs in human hair, allowing high analytical specificity and sensitivity. The novel finding of hair THs levels from individuals suffering from chronic stress in burnout underscores the relevance of this method for medical and psychological research.

Online solid-phase extraction liquid chromatography–mass spectrometry of hair cortisol using a surrogate analyte

Online SPE LC–MS with 13C3-cortisol as a surrogate analyte was developed, validated and applied for obtaining hair cortisol levels of 114 healthy volunteers. The first 3 cm from a posterior vertex position were analyzed as three individual segments resulting in 310 hair cortisol levels, which were used, after log transformation, to predict a range of values observed in future. The median value of hair cortisol was 4.76 pg/mg. The employed method allowed simple processing, high throughput and may be readily expanded to analyze additional steroid compounds in hair.

Automated online solid-phase extraction-liquid chromatography mass spectrometric analysis of dithianon in water.

An automated online solid-phase extraction-liquid chromatography mass spectrometry (SPE-LC/MS) method was developed for the quantification of dithianon in surface water samples, using warfarin as internal standard. The method was developed on a liquid chromatography (LC) system with Flexible Cube interfaced to a quadrupole time-of-flight (Q-TOF) mass spectrometer. A small volume of acidified water (1 mL) was spiked with internal standard, pre-concentrated online on polymeric cartridges and analyzed by full-scan MS in high-resolution conditions. The quantitative data were obtained by [M]-• of dithianon and [M - H]- of warfarin, used as internal standard. The chromatographic separation was performed on a C18 column with a gradient mobile phase consisting of acetonitrile and water containing 0.05% acetic acid. The method was validated to measure concentrations of dithianon in the range of 0.010-4 µg L-1 in surface water samples. Twenty real water samples, collected from Torrente Novella, Val di Non (TN, Northern Italy), during fungicide treatments of large apple orchards, were analyzed. All samples were kept in glass bottles and stored in the lab at -20°C until analysis. It was found that in all samples dithianon was undetectable: if it is present, its concentration was lower than the limit of detection (LOD) (0.008 µg L-1.To investigate the stability of dithianon, a series of water samples were spiked at different concentrations and analyzed after different storage conditions. Results suggested that dithianon is not stable in water stored at -20°C at neutral or basic pH, but the addition of acetic acid to pH = 3.5 increases its stability to at least two weeks.

Development of on-line molecularly imprinted solid phase extraction-liquid chromatography-mass spectrometry for triazine analysis in corn samples

A highly selective method for the analysis of triazine herbicides in corn samples based on molecularly imprinted solid phase extraction (MISPE) has been developed.

Aqueous photodegradation of antibiotic florfenicol: kinetics and degradation pathway studies.

The occurrence of antibacterial agents in natural environment was of scientific concern in recent years. As endocrine disrupting chemicals, they had potential risk on ecology system and human beings. In the present study, the photodegradation kinetics and pathways of florfenicol were investigated under solar and xenon lamp irradiation in aquatic systems. Direct photolysis half-lives of florfenicol were determined as 187.29 h under solar irradiation and 22.43 h under xenon lamp irradiation, respectively. Reactive oxygen species (ROS), such as hydroxyl radical (·OH) and singlet oxygen ((1)O2) were found to play an important role in indirect photolysis process. The presence of nitrate and dissolved organic matters (DOMs) could affect photolysis of florfenicol in solutions through light screening effect, quenching effect, and photoinduced oxidization process. Photoproducts of florfenicol in DOMs solutions were identified by solid phase extraction-liquid chromatography-mass spectrometry (SPE-LC-MS) analysis techniques, and degradation pathways were proposed, including photoinduced hydrolysis, oxidation by (1)O2 and ·OH, dechlorination, and cleavage of the side chain.

New insights into atrazine degradation by cobalt catalyzed peroxymonosulfate oxidation: Kinetics, reaction products and transformation mechanisms

The widespread occurrence of atrazine in waters poses potential risk to ecosystem and human health. In this study, we investigated the underlying mechanisms and transformation pathways of atrazine degradation by cobalt catalyzed peroxymonosulfate (Co(II)/PMS). Co(II)/PMS was found to be more efficient for ATZ elimination in aqueous solution than Fe(II)/PMS process. ATZ oxidation by Co(II)/PMS followed pseudo-first-order kinetics, and the reaction rate constant (kobs) increased appreciably with increasing Co(II) concentration. Increasing initial PMS concentration favored the decomposition of ATZ, however, no linear relationship between kobs and PMS concentration was observed. Higher efficiency of ATZ oxidation was observed around neutral pH, implying the possibility of applying Co(II)/PMS process under environmental realistic conditions. Natural organic matter (NOM), chloride (Cl−) and bicarbonate (HCO3−) showed detrimental effects on ATZ degradation, particularly at higher concentrations. Eleven products were identified by applying solid phase extraction-liquid chromatography–mass spectrometry (SPE-LC/MS) techniques. Major transformation pathways of ATZ included dealkylation, dechlorination-hydroxylation, and alkyl chain oxidation. Detailed mechanisms responsible for these transformation pathways were discussed. Our results reveal that Co(II)/PMS process might be an efficient technique for remediation of groundwater contaminated by ATZ and structurally related s-triazine herbicides.

Online solid-phase extraction–liquid chromatography–mass spectrometry to determine free sterols in human serum

An automated method for analyzing free non-cholesterol sterols in human serum using online solid phase extraction–liquid chromatography–mass spectrometry is proposed herein. The method allows the determination of three phytosterols (sitosterol, stigmasterol and campesterol) and two cholesterol precursors (desmosterol and lanosterol). The analysis of sterols in human serum is critical in the study of cholesterol-related disorders, such as inherited familial hypercholesterolemias. Special effort was made to isolate the analytes from the serum lipoproteins, their natural conveyance through the bloodstream. The sample treatment consisted of a Bligh–Dyer extraction followed by dilution of the extract. This treatment allowed the sample to be injected into the online system and ensured the correct detection of the analytes, while avoiding the matrix effects commonly related to serum samples.The analytical performance showed linear ranges that covered two orders of magnitude, with correlation coefficients above 0.99. Limits of detection and quantification ranged from 0.2ng/mL to 13ng/mL and from 1.0ng/mL to 43ng/mL, respectively. Recovery when spiking serum with a half or a tenth of the average concentration reported in human serum ranged from 99% to 111% and from 102% to 120%, respectively. Intra-day precision and inter-day precision were below 20%.

Trace determination of primary nerve agent degradation products in aqueous soil extracts by on-line solid phase extraction–liquid chromatography–mass spectrometry using ZrO2 for enrichment

A method for determination of the primary nerve agent degradation products ethyl-, isopropyl-, isobutyl-, cyclohexyl- and pinacolyl methylphosphonic acid in aqueous soil extracts has been developed utilizing on-line solid phase extraction-liquid chromatography and mass spectrometry (SPE–LC–MS). Four different stationary phases (ZrO2, TiO2, polymeric mixed mode anion exchange and porous graphitic carbon) were investigated for their suitability as SPE materials in the on-line SPE–LC–MS setup. Zirconium dioxide was chosen due to its high affinity for the alkyl methylphosphonic acids (AMPAs), and its compatibility with LC–MS. Aqueous soil extracts were acidified with 0.1% acetic acid and aliquots of 300μL were injected on a 2mm×10mm ZrO2 column. Separation of the analytes was performed on a reversed phase column with acetonitrile/water gradient and 15mM ammonium acetate. Method validation was performed with the analytes added to an aqueous extract of a loam soil, and the AMPAs could be determined at concentrations as low as 0.05–0.5μgL−1. The method was linear (R2>0.995) from the limit of quantification (LOQ) to 100×LOQ, and the within assay repeatability was below 10% and 5% relative standard deviation at LOQ and 50×LOQ, respectively. The developed method was employed for determination of the AMPAs which had been added to the aqueous extracts of five different soil types from cultivated and uncultivated areas. The obtained recoveries showed that the analytes could be determined at the sensitivities achieved in the method validation in four of the extracts. For the first time, we have demonstrated a method capable of detecting primary nerve agent degradation products at sub ppb levels in the aqueous extracts of various soils. The method requires no sample preparation after soil extraction other than pH adjustment of the aqueous extract.

Degradation of ciprofloxacin and sulfamethoxazole by ferrous-activated persulfate: Implications for remediation of groundwater contaminated by antibiotics

The wide occurrence of antibiotics in groundwater raised great scientific interest as well as public awareness in recent years due to their potential ability to spread antibiotic resistant gene and pose risk to humans. The present study investigated the ferrous ion (Fe(II)) activated decomposition of persulfate (S2O82−), as a potential in situ chemical oxidation (ISCO) approach, for remediation of groundwater contaminated by antibiotics. Fe(II)-persulfate mediated ciprofloxacin (CIP) degradation was found to be more efficient than sulfamethoxazole (SMX) at near neutral pH (pH6.0), probably due to the higher electric density in CIP molecule and its ability to form complex with Fe(II) as a ligand. Hydroxyl (HO) and sulfate radical (SO4−) were determined to be responsible for the degradation of CIP and SMX in Fe(II)-persulfate system by molecular probes. No enhancement in the degradation of CIP was observed when citrate (CA), ethylenediaminetetraacetate (EDTA) and (S,S)-ethylenediamine-N,N′-disuccinate (EDDS) were used as Fe(II) chelating agents in Fe(II)-persulfate system. For SMX, CA and EDTA accelerated the degradation by Fe(II)-persulfate. Degradation of antibiotics in river water matrix was nearly the same as that in Milli-Q water, implying the possibility of using Fe(II)-persulfate for antibiotics depletion under environmentally relevant condition. A comparison of the degradation efficiency of SMX with other sulfonamides and sulfanilic acid indicated that the heterocyclic ring has a large impact on the degradation of sulfonamides. Transformation products of CIP and SMX by Fe(II)-persulfate were analyzed by solid phase extraction–liquid chromatography–mass spectrometry (SPE–LC–MS) technique. Based on the intermediate products, Fe(II)-persulfate mediated CIP degradation pathways were tentatively proposed.

Photoreactivity of hydroxylated multi-walled carbon nanotubes and its effects on the photodegradation of atenolol in water

In spite of the increasing concerns about the fate of pharmaceuticals and personal care products (PPCPs) and the nanomaterial pollution in aquatic ecosystem, the effects of carbon nanotubes on the photochemical transformation of PPCPs are less considered. In this study, the photochemical production of reactive oxygen species (ROS) were examined in colloidal dispersions of hydroxylated multi-walled carbon nanotubes (MWNT-OH) under simulated solar irradiation using a Xenon lamp. Two kinds of ROS, 1O2 and OH, were confirmed by their molecular probes, furfuryl alcohol (FFA) and p-chlorobenzoic acid (PCBA). The steady-state concentrations of 1O2 and OH were calculated as 1.30×10−14M and 5.02×10−16M, respectively. The effects of MWNT-OH on photodegradation of atenolol (ATL) were investigated in the presence of natural water components, i.e., dissolved organic matters (DOMs), nitrate (NO3-) and ferric ions (Fe3+). Photoproducts of atenolol were identified by solid phase extraction-liquid chromatography–mass spectrometry (SPE-LC–MS) analysis techniques. Three potential photochemical pathways of atenolol, including the hydroxylation on aromatic ring, the loss of amide group and the cleavage of ether oxygen bond as well as di-polymerization of reaction intermediates were tentatively proposed. Using the radical quenching method, reaction with OH was determined as the major photolysis pathway of atenolol in irradiated MWNT-OH suspensions. These findings of the production of ROS and their effects on the photodegradation of organic contaminants provided useful information for assessing environmental risk of MWNT-OH.

On-line solid phase extraction-liquid chromatography–mass spectrometry for trace determination of nerve agent degradation products in water samples

Three primary nerve agent degradation products (ethyl-, isopropyl- and pinacolyl methylphosphonic acid) have been determined in water samples using on-line solid phase extraction-liquid chromatography and mass spectrometry (SPE-LC–MS) with electrospray ionisation. Porous graphitic carbon was employed for analyte enrichment followed by hydrophilic interaction chromatography. Diethylphosphate was applied as internal standard for quantitative determination of the alkyl methylphosphonic acids (AMPAs). By treating the samples with strong cation-exhange columns on Ba, Ag and H form, the major inorganic anions in water were removed by precipitation prior to the SPE-LC–MS determination. The AMPAs could be determined in tap water with limits of detection of 0.01–0.07μgL−1 with the [M−H]− ions extracted at an accuracy of ±5mDa. The within and between assay precisions at analyte concentrations of 5μgL−1 were 2–3%, and 5–9% relative standard deviation, respectively. The developed method was employed for determination of the AMPAs in three natural waters and a simulated waste water sample, spiked at 5μgL−1. Recoveries of ethyl-, isopropyl- and pinacolyl methylphosphonic acid were 80–91%, 92–103% and 99–106%, respectively, proving the applicability of the technique for natural waters of various origins.

A novel method for the identification of illegal cooking oil (1): detection of three capsaicinoids with liquid chromatography-mass spectrometry

Illegal cooking oil (ICO, also named swill-cooked dirty oil) has recently become a serious food safety problem in China. Now, the identification method of ICO is also a hot research area. Owning to the special eating habits of Chinese people, cayenne is widely used in catering business. Capsaicinoids are main spicy compounds in cayenne. So, they are potential evaluation indices for the identification of ICO. In this study, a solid phase extraction-liquid chromatography-mass spectrometry (SPE-LC-MS) method has been developed to detect the trace residues of three capsaicinoids (capsaicin, dihydrocapsaicin and nonylic acid vanillylamide) in cooking oil. The oil sample was first extracted with 20 g/L sodium hydroxide, the C18 SPE cartridge was then used to clean-up the sample and enrich the analytes before the liquid chromatography-mass spectrometry (LC-MS) detection. With this method, sixty seven blind samples provided by China National Center for Food Safety Risk Assessment were analyzed. The results showed that the capsaicinoids are good evaluation indices for the identification of ICO. In all the 48 ICO samples, 36 samples were successfully recognized. All the 19 normal oil samples were accurately identified. This method has been chosen and authorized as one of the four standard instrumental identification methods for ICO by the National Ministry of Health of China.

Aquatic photodegradation of sunscreen agent p-aminobenzoic acid in the presence of dissolved organic matter

Dissolved organic matter (DOM) is an important photosensitizer for the phototransformation of organic contaminants in sunlit natural waters. This article focuses on the photolysis kinetics and mechanism of sunscreen agent p-aminobenzoic acid (PABA) in the presence of four kinds of DOM; Suwannee River fulvic acid (SRFA), Suwannee River humic acid (SRHA), Nordic Lake fulvic acid (NOFA) and Nordic Lake humic acid (NOHA). It is evident that direct photolysis of PABA is highly pH-dependent because different species of PABA have different electrical densities on the ring system. The presence of four kinds of DOM inhibits the photolysis of PABA primarily due to their light screening effect. Meanwhile, a complex interaction involving energy transfer, triplet carbonyl group induced electron transfer, and amino acid induced proton abstraction between PABA and DOM is verified by competition kinetics experiments and density functional theory (DFT) computation. In addition, DOM-induced singlet oxygen (1O2) and hydroxyl radical (OH) are determined to play an insignificant role in PABA photolysis by competition dynamics method. Photoproducts identification using solid phase extraction–liquid chromatography–mass spectrometry (SPE–LC–MS) techniques reveals that the distribution of the photoproducts could not be affected by the addition of DOM. Two photodegradation pathways of PABA are temporarily proposed, in which the di(tri)-polymerization of intermediates are the dominant pathway whereas the oxidation of amino group to nitryl followed by hydroxylation is a minor process. Our findings reveal that direct photolysis is the dominant transformation pathway of PABA in natural sunlit waters, while the presence of DOM could evidently influence such process by light screening effect, energy transfer, electron transfer and proton abstraction mechanism. The findings in this study provide useful information for understanding of interaction between DOM and organic contaminants.

Determination of Nine Sensitizing Disperse Dyes in Dyeing Wastewater by Solid Phase Extraction-Liquid Chromatography-Mass Spectrometry

Determination of Nine Sensitizing Disperse Dyes in Dyeing Wastewater by Solid Phase Extraction-Liquid Chromatography-Mass Spectrometry

Nitrate-induced photodegradation of atenolol in aqueous solution: Kinetics, toxicity and degradation pathways

The extensive utilization of β-blockers worldwide led to frequent detection in natural water. In this study the photolysis behavior of atenolol (ATL) and toxicity of its photodegradation products were investigated in the presence of nitrate ions. The results showed that ATL photodegradation followed pseudo-first-order kinetics upon simulated solar irradiation. The photodegradation was found to be dependent on nitrate concentration and increasing the nitrate from 0.5mML−1 to 10mML−1 led to the enhancement of rate constant from 0.00101min−1 to 0.00716min−1. Hydroxyl radical was determined to play a key role in the photolysis process by using isopropanol as molecular probe. Increasing the solution pH from 4.8 to 10.4, the photodegradation rate slightly decreased from 0.00246min−1 to 0.00195min−1, probably due to pH-dependent effect of nitrate-induced OH formation. Bicarbonate decreased the photodegradation of ATL in the presence of nitrate ions mainly through pH effect, while humic substance inhibited the photodegradation via both attenuating light and competing radicals. Upon irradiation for 240min, only 10% reduction of total organic carbon (TOC) can be achieved in spite of 72% transformation rate of ATL, implying a majority of ATL transformed into intermediate products rather than complete mineralization. The main photoproducts of ATL were identified by using solid phase extraction–liquid chromatography–mass spectrometry (SPE–LC–MS) techniques and possible nitrate-induced photodegradation pathways were proposed. The toxicity of the phototransformation products was evaluated using aquatic species Daphnia magna, and the results revealed that photodegradation was an effective mechanism for ATL toxicity reduction in natural waters.

Determination of Antofloxacin in Human Plasma by Solid Phase Extraction-Liquid Chromatography-Mass Spectrometry

A new and specific method has been developed for the determination of antofloxacin in human plasma by solid phase extraction-liquid chromatography coupled with tandem spectrometry.The samples were extracted and purified by wean anion solid phase extraction.The eluent was dried and reconstituted before analysis.The separation was performed on an Agilent Eclipse plus C8 column,with a mobile phase consisting of 10 mmol/L ammonium acetate(pH 3.5)-methanol(35∶65,V/V) at a flow of 0.35 mL/min.Identification and quantification were achieved by LC-MS/MS in a positive mode and multiple reactions monitoring(MRM).Good linearity was observed in a range of 7.0-5080 μg/L with a correlation coefficient of more than 0.996.The detection limit was 0.5 μg/L.Sample recovery was 77.6%,and inter-day coefficient of variation was less than 7.9%.The proposed method has been applied to the determination of antofloxacin in plasma after subjects were orally given 400 mg of antofloxacin tablets.

Development of Liquid Chromatography−Electrospray Mass Spectrometry for the Determination of Patulin in Apple Juice: Investigation of Its Contamination Levels in Japan

Patulin is a mycotoxin produced by mainly Penicillium species, for example, P. expansum, and Aspergillus species. There are several reports of patulin contamination in apple juice. Last year, the Ministry of Health, Labour and Welfare of Japan set the maximum allowable level of patulin in apple juice at 50 ppb and decided that the measurement of patulin levels in apple juice products should be conducted. To this end, a simple, accurate, and selective analytical method for the detection of patulin at levels lower than 5 ppb, the detection limit, is desired. This paper reports the development of an analytical method that employs solid-phase extraction-liquid chromatography-mass spectrometry (SPE-LC-MS). When MS measurements were conducted with the selected ion monitoring (SIM) mode, the pseudomolecular ions at m/z 153 and 156 were used to monitor patulin and (13)C(3)-labeled patulin, respectively. The detection limit (S/N = 3) and the quantification limit (S/N = 10) of patulin at injection levels into LC-MS were 12.5 and 25 pg, respectively. However, when the actual sample was applied for the analysis based on the developed method including the sample preparation, the detection limit (S/N = 3) and quantification limit (S/N = 10) were 2.5 and 5 pg in sample, respectively. The calibration curve obtained for concentrations ranging from 5 to 500 ppb showed good linearity with a coefficient of determination (r (2)) of 0.999. In addition, the recovery was >95% when an internal standard was used. The method was applied to the analysis of 76 apple juice samples from Japan, and as a result, patulin levels ranging from <1.0 to 45 ppb (detection frequency = 15/76) were detected. In this study, it was found that patulin was a greater contaminant in concentration/reduction than in "not from concentrate" apple juice.