Analysis of amprolium by hydrophilic interaction liquid chromatography–tandem mass spectrometry

We present a fast liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for the analysis of the coccidiostat amprolium in food samples. Tandem mass spectrometry in a triple quadrupole was used for quantitative purposes, and the information from multiple-stage mass spectrometry in an ion-trap mass analyzer contributed to fragmentation studies. Hydrophilic interaction liquid chromatography (HILIC) in a Fused-Core™ column using isocratic elution (acetonitrile:formic acid/ammonium formate buffer pH 4, 50 mM (60:40)) successfully analyzed this compound in less than 3 min. The HILIC system was coupled to heated electrospray-MS/MS using highly selective-selected reaction monitoring (H-SRM) to improve sensitivity and selectivity for the analysis of amprolium, after a simple sample treatment based on an “extract and shoot” strategy. Accurate mass measurements were performed to identify the interfering compound responsible for causing matrix ion enhancement in the signal of amprolium. The addition of l-carnitine (the interfering compound) (1 μg L⁻¹) to standards and sample extracts allowed the use of the external calibration method for quantitative purposes. The LC–MS/MS (H-SRM) method showed good precision (relative standard deviation, RSD, lower than 13%), accuracy and linearity and allowed the determination of amprolium down to the ppb level (LODs between 0.1 and 0.6 μg kg⁻¹).     

Analysis of chlormequat and mepiquat by hydrophilic interaction chromatography coupled to tandem mass spectrometry in food samples

In this work a LC–MS/MS method for the determination of two quaternary ammonium growth regulators (chlormequat and mepiquat) in food is reported. The separation was based on hydrophilic interaction liquid chromatography (HILIC) without the use of ion-pair reagents. A gradient elution of acetonitrile and formic acid/ammonium formate buffer from 60 to 40% acetonitrile was enough to achieve a resolution >1.5 in less than 4.0 min. The HILIC system was coupled to a triple quadrupole mass spectrometer equipped with a heated electrospray probe (H-ESI) providing sub-pg LODs in SRM mode. A straightforward sample treatment (SPE C18 clean-up) was enough to provide MLODs at low ppb levels when analysing a range of food samples that covered different kinds of matrices such as fresh fruit, vegetables, fruit juices, baby food, bread, coffee and beer. Chlormequat was found in seven samples (0.8–126 ng/g) but mepiquat was only detected in bread and coffee samples (0.9–166 ng/g).     

Simultaneous determination of 3-monochloropropane-1,2-diol and acrylamide in food by gas chromatography-triple quadrupole mass spectrometry with coupled column separation

Both 3-monochloropropane-1,2-diol (3-MCPD) and acrylamide are contaminants found in heat-processed foods and their related products. A quantitative method was developed for the simultaneous determination of both contaminants in food by gas chromatography-triple quadrupole mass spectrometry (GC–MS/MS). The analytes were purified and extracted by the matrix solid-phase dispersion extraction (MSPDE) technique with Extrelut NT. A coupled column (a 3 m Innowax combined with a 30 m DB-5 ms) was developed to separate both compounds efficiently without derivatization. Triple quadrupole mass spectrometry in multiple reaction monitoring mode (MRM) was applied to suppress matrix interference and obtain good sensitivity in the determination of both analytes. The limit of detection (LOD) in the sample matrix was 5 μg kg⁻¹ for 3-MCPD or acrylamide. The average recoveries for 3-MCPD and acrylamide in different food matrices were 90.5–107% and 81.9–95.7%, respectively, with the intraday relative standard deviations (RSDs) of 5.6–13.5% and 5.3–13.4%, respectively. The interday RSDs were 6.1–12.6% for 3-MCPD and were 5.0–12.8% for acrylamide. Both contaminants were found in samples of bread, fried chips, fried instant noodles, soy sauce, and instant noodle flavoring. Neither 3-MCPD nor acrylamide was detected in the samples of dairy products (solid or liquid samples) and non-fried instant noodles.     

Screening of antibiotics in surface and wastewater samples by ultra-high-pressure liquid chromatography coupled to hybrid quadrupole time-of-flight mass spectrometry

The potential of ultra-high-pressure liquid chromatography (UHPLC) coupled to hybrid quadrupole time-of-flight mass spectrometry (QTOF–MS) for the screening and confirmation of antibiotics in water samples is illustrated in this paper. UHPLC presents several advantages over conventional liquid chromatography as it generates narrow peaks (increasing peak height and improving sensitivity) and reduces chromatographic runs. Regarding QTOF–MS, its increased mass resolution, high sensitivity in full-spectrum acquisition mode and mass accuracy, in both MS and MS/MS modes, make this technique ideal for the detection and reliable confirmation of organic contaminants in environmental samples. After a solid-phase extraction using Oasis HLB cartridges, UHPLC–QTOF–MS has been applied in this work to several types of water samples (surface water and influent and effluent wastewaters). Several antibiotics were found in the samples, such as ofloxacin, ciprofloxacin, clarythromycin or erythromycin, among others. Moreover, the full spectrum data provided by TOF–MS acquisition has enabled searching for many other pharmaceuticals that could be present in the samples in a “post-target” way. This approach has allowed the detection and confirmation of paracetamol, omeprazole and codeine, among others. UPLC–QTOF–MS has been shown as an attractive and efficient hyphenated technique for the rapid detection and confirmation of pharmaceuticals in water with very little sample handling.     

Method validation of microcystins in water and tissue by enhanced liquid chromatography tandem mass spectrometry

A liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI–MS/MS) method has been developed and validated to identify and quantify trace levels of cyanotoxins or microcystins (MC) in water, bivalves and fish tissue with enhanced sensitivity and specificity. The method enables confirmation and quantification of six MCs (MC-LA, LF, LR, LW, RR and YR) with a single chromatographic run. The applied chromatography also allows determination of certain MC metabolites (Desmethyl-LR and -RR). By using LC-ESI–MS/MS in multiple reaction monitoring (MRM) mode, the limit of detection and quantitation for the microcystins studied, were determined to be between 0.2 and 1 pg on column (5:1 S/N ratio). These values are below the 2 pg detection limits found in the available literature.     

High-throughput intracellular pteridinic profiling by liquid chromatography–quadrupole time-of-flight mass spectrometry

Pteridines are a diverse family of endogenous metabolites that may serve as useful diagnostic biomarkers for disease. While many preparative and analytical techniques have been described for analysis of selected pteridines in biological fluids, broad intracellular pteridine detection remains a significant analytical challenge. In this study, a novel, specific and sensitive extraction and high performance liquid chromatography–quadrupole time-of-flight mass spectrometry (HPLC–QTOF MS) method was developed to simultaneously quantify seven intracellular pteridines and monitor 18 additional, naturally-occurring intracellular pteridines. The newly developed method was validated through evaluation of spiked recoveries (84.5–109.4%), reproducibility (2.1–5.4% RSD), method detection limits (0.1–3.0 μg L⁻¹) and limits of quantitation (0.1–1 μg L⁻¹), and finally application to non-small cell lung cancer A549 cells. Twenty-three pteridine derivatives were successfully detected from cell lysates with an average RSD of 12% among culture replicates. Quantified intracellular pteridine levels ranged from 1 to 1000 nM in good agreement with previous studies. Finally, this technique may be applied to cellular studies to generate new biological hypotheses concerning pteridine physiological and pathological functions as well as to discovery new pteridine-based biomarkers.     

Multi-class pesticide analysis in human hair by gas chromatography tandem (triple quadrupole) mass spectrometry with solid phase microextraction and liquid injection

A method for the simultaneous detection and quantification of 22 pesticides from different chemical classes was developed using solid-phase microextraction (SPME) and gas chromatography tandem (triple quadrupole) mass spectrometry. Pesticides were extracted from 50 mg of pulverized hair with acetonitrile. The extract was submitted to two successive steps of direct immersion-SPME at 30 °C and 90 °C or to a liquid injection without SPME in order to obtain optimized conditions for each of the 22 analytes investigated. Validation parameters were significantly influenced by both the injection mode (SPME vs liquid injection) and the temperature of SPME. Limits of quantification ranged from 0.05 pg mg⁻¹ for trifluralin to 10 pg mg⁻¹ for pentachlorophenol. The application of the validated method to the analysis of samples collected from non-occupationally exposed volunteers demonstrated the presence of pesticides in all the samples tested. Altogether, 13 different analytes were detected at concentration above the limit of quantification.     

Optimization of antibiotic analysis in water by solid-phase extraction and high performance liquid chromatography–mass spectrometry/mass spectrometry

This paper describes the development of an optimized method based on solid-phase extraction (SPE) followed by liquid chromatography–electrospray ionization tandem mass spectrometry (LC–MS/MS) for the simultaneous analysis of ten antibiotic compounds including tetracyclines, sulfonamides, macrolides and quinolones. LC–MS/MS sensitivity has been optimized by alterations to both LC and MS operations. Of the two high resolution columns tested, Waters Symmetry C₁₈ endcapped and Agilent Zorbax Bonus-RP, the latter was found to show better performance in producing sharp peaks and clear separation for most of the target compounds. Optimization of the MS fragmentation collision and cone energy enhanced the peak areas of the target analytes. The recovery of the target compounds from water samples was most efficient on Waters Oasis HLB SPE cartridge, while methanol was shown to be the most suitable solvent for desorbing the compounds from SPE. In addition, acidification of samples prior to SPE was shown to enhance the recovery of the compounds. To ensure a satisfactory recovery, the flow rate through SPE should be maintained at ≤10 mL min⁻¹. The method was successfully applied to the analysis of antibiotics from environmental water samples, with concentrations being <LOD in tap water, between <LOD to 28 ng L⁻¹ in river water and between <LOD to 230 ng L⁻¹ in sewage effluent.     

A strategy for the systematic development of a liquid chromatographic mass spectrometric screening method for polymer electrolyte membrane degradation products using isocratic and gradient phase optimized liquid chromatography

Within the scope of research for target and non-target LC–MS/MS analysis of membrane degradation products of polymer electrolyte membrane fuel cells, a systematic method development for the separation of structurally similar compounds was performed by phase optimized liquid chromatography. Five different stationary phases with different selectivities were used. Isocratic separation for 4-hydroxybenzoic acid, isophthalic acid, terephthalic acid, 4-hydroxybenzaldehyde and 4-formylbenzoic acid was achieved on a C18 and a Phenyl phase. Using the PRISMA model the separation efficiency was optimized. This was achieved on a serially connected mixed stationary phase composed of 30 mm C18, 150 mm Phenyl and 60 mm C30. For the LC–MS screening of unknown degradation products from polymer electrolyte membranes in the product water of a fuel cell, a solvent gradient is mandatory for less polar or later eluting compounds. By means of 4-mercaptobenzoic acid it could be shown that a solvent gradient can be applied in order to elute later eluting compounds in a short time. The adaptability of this method for the qualitative analysis by target and non-target LC–MS/MS screening has been shown by means of 4-hydroxybenzoic acid. The combination of solvent gradient and isocratic conditions makes this approach attractive for the purpose of a screening method for known and unknown analytes in a water sample.     

Determination of 2,6-dichlorobenzamide and its degradation products in water samples using solid-phase extraction followed by liquid chromatography–tandem mass spectrometry

An analytical method was developed for the determination of 2,6-dichlorobenzamide (BAM) and five degradation products thereof including 2-chlorobenzamide (OBAM), 2,6-dichlorobenzoic acid (DCBA), 2-chlorobenzoic acid (OBA), benzoic acid (BA) and benzamide (BAD) in water samples. Solid-phase extraction was combined with liquid chromatography coupled to tandem mass spectrometry using electrospray ionisation. Groundwater spiked at a concentration of 1.0 μg/L gave recoveries on day 1 between 91 and 102% (relative standard deviation: 2.2–26.5%) for OBAM, BAM, DCBA, BA and OBA, while BAD showed a somewhat lower recovery of 60% (relative standard deviation: 25%). Corresponding figures on day 3 gave recoveries of 97–110% (relative standard deviation: 3–22%) for OBAM, BAM, DCBA, BA and OBA, while BAD had a recovery of 51% (relative standard deviation: 4%). The final SPE-LC–MS/MS method had a LOD_Method of 0.009, 0.007, 0.010, 0.021, 0.253 and 0.170 μg/L groundwater for BAD, OBAM, BAM, DCBA, BA and OBA and a LOQ_Method of 0.030, 0.023, 0.035, 0.071, 0.842 and 0.565 μg/L groundwater in the same order of appearance. Analysis of three different Danish groundwaters confirmed the occurrence of BAM at levels exceeding the threshold value of 0.1 μg/L, while no degradation products were found above LOD_Method.     

A simple hollow fiber renewal liquid membrane extraction method for analysis of sulfonamides in honey samples with determination by liquid chromatography–tandem mass spectrometry

A sensitive and precise analysis using hollow fiber renewal liquid membrane (HFRLM) extraction followed by high performance liquid chromatography–tandem mass spectrometry (LC–MS/MS) is described for determination of five sulfonamides in honey samples. In this procedure, the organic solvent introduced directly into the sample matrix extracts the sulfonamides and carries them over the polypropylene porous membrane. An organic solvent is immobilized inside the polypropylene porous membrane, leading to a homogeneous phase. The stripping phase at higher pH in the lumen of the membrane promotes the ionization of the target compounds releasing them to this phase. The most important parameters affecting the extraction efficiency were optimized by multivariable designs (pH and sample mass, pH and buffer for stripping phase, extraction temperature and time, type and volume of extractor solvent and use of salt to saturate the sample). Detection limits in the range of 5.1–27.4 μg kg⁻¹ and linearity coefficient of correlation higher than 0.987 were obtained for the target analytes. The results obtained for the proposed method show that HFRLM–LC–MS/MS can be used for determination of the five sulfonamides studied in honey samples with excellent precision, accuracy, practicality and short analysis time.     

On-line solid-phase extraction of large-volume injections coupled to liquid chromatography-tandem mass spectrometry for the quantitation and confirmation of 14 selected trace organic contaminants in drinking and surface water

We describe the development and validation of an on-line solid-phase extraction of large-volume injections coupled to liquid chromatography-tandem mass spectrometry method for the simultaneous quantitation and confirmation of 14 selected trace organic contaminants in drinking and surface water. Selected compounds were: anti-infectives (clarithromycin, sulfamethoxazole and trimethoprim), an anticonvulsant (carbamazepine) and its transformation product 10,11-dihydrocarbamazepine, an antihypertensive (enalapril), antineoplastics (cyclophosphamide and methotrexate), herbicides (atrazine, cyanazine, and simazine) and two of their transformation products (deethylatrazine and deisopropylatrazine) and an antiseptic (triclocarban). The breakthrough volume determinations showed that out of all the investigated sorbents, the Strata-X on-line solid-phase extraction column showed the best performance. The method used a load volume of 10.0 mL and was validated using the corresponding matrices, yielding for most compounds, R² > 0.99. Extraction recoveries ranged from 60 to 109%. The intra- and inter-day precision were <14 and <16%, respectively. The method detection limits ranged from 0.6 to 6 ng L⁻¹. Matrix effects were in general low. The performance of the on-line method was demonstrated with the analysis of real water samples. The application of alternative techniques of confirmation was also explored using accurate mass measurements on a time-of-flight mass spectrometer and the data-dependent reverse energy ramp scan on a triple quadrupole.     

Method validation and comparison of acetonitrile and acetone extraction for the analysis of 169 pesticides in soya grain by liquid chromatography–tandem mass spectrometry

An acetonitrile-based extraction method for the analysis of 169 pesticides in soya grain, using liquid chromatography–tandem mass spectrometry (LC–MS/MS) in the positive and negative electrospray ionization (ESI) mode, has been optimized and validated. This method has been compared with our earlier published acetone-based extraction method, as part of a comprehensive study of both extraction methods, in combination with various gas chromatography–(tandem) mass spectrometry [GC–MS(/MS)] and LC–MS/MS techniques, using different detection modes. Linearity of calibration curves, instrument limits of detection (LODs) and matrix effects were evaluated by preparing standards in solvent and in the two soya matrix extracts from acetone and acetonitrile extractions, at seven levels, with six replicate injections per level. Limits of detection were calculated based on practically realized repeatability relative standard deviations (RSDs), rather than based on (extrapolated) signal/noise ratios. Accuracies (as % recoveries), precision (as repeatability of recovery experiments) and method limits of quantification (LOQs) were compared. The acetonitrile method consists of the extraction of a 2-g sample with 20 mL of acetonitrile (containing 1% acetic acid), followed by a partitioning step with magnesium sulphate and a subsequent buffering step with sodium acetate. After mixing an aliquot with methanol, the extract can be injected directly into the LC–MS/MS system, without any cleanup. Cleanup hardly improved selectivity and appeared to have minor changes of the matrix effect, as was earlier noticed for the acetone method. Good linearity of the calibration curves was obtained over the range from 0.1 or 0.25 to 10 ng mL⁻¹, with r² ≥ 0.99. Instrument LOD values generally varied from 0.1 to 0.25 ng mL⁻¹, for both methods. Matrix effects were not significant or negligible for nearly all pesticides. Recoveries were in the range 70–120%, with RSD ≤ 20%. If not, they were still mostly in the 50–70% range, with good precision (RSD ≤ 20%). The method LOQ values were most often 10 μg kg⁻¹ for almost all pesticides, with good repeatability RSDs. Apart from some minor pros and cons, both compared methods are fast, efficient and robust, with good method performances. The two methods were applied successfully in a routine analysis environment, during surveys in 2007 and 2008.     

Determination of thyreostats in urine and thyroid gland by ultra high performance liquid chromatography tandem mass spectrometry

Thyreostatic compounds could be illegally administered to animals in order to obtain a weight gain due to a higher retention of water in the edible tissue and the gastro-intestinal tract. In the European Union their use for animal production is banned since 1981. Recently a highly sensitive method exploiting the determination of thyreostats with 3-iodobenzylbromide prior to purification to determine thyreostats in urine and other matrices was reported. For the first time, the UPLC instrumentation was used to separate the 3-iodobenzyl derivatives of various thyreostats. The deuterated internal standards tapazole-d₃ and propylthiouracil-d₅ were for the first time used for the quantification of tapazole, thiouracil, methylthiouracil, propylthiouracil, phenylthiouracil and mercaptobenzimidazole. The confirmative quantitative liquid chromatographic tandem mass spectrometric (LC–MS/MS) method was validated according to Commission Decision 2002/657/EC. The decision limit (CCα) and the detection capability (CCβ) were found to be for all compounds below the recommended value of 10 μg kg⁻¹.     

Trace analysis of isothiazolinones in water samples by large-volume direct injection liquid chromatography tandem mass spectrometry

Isothiazolinones are used as preservatives, biocides and disinfectants in a variety of industrial and domestic applications. Some of the isothiazolinones are difficult to isolate from water due their high polarity. A sensitive and selective analytical method was developed and optimized for the determination of sub-μg/L levels of three isothiazolinones in water samples. Three isothiazolinones are described in this paper: 2-methyl-3-isothiazolinone, 5-chloro-2-methyl-3-isothiazolinone and 4,5-dichloro-2-methyl-3-isothiazolinone. The analytical method involves a robust large-volume direct on-column loop injection of 2 mL on an Aqua ODS HPLC column and tandem MS detection (HPLC–MS/MS). After filtration, samples are directly injected without further pretreatment. Detection limits of the individual target compounds were between 0.03 and 0.1 μg/L employing Multi-Reaction Monitoring (MRM) mass spectrometry. Based on the constant ratio of two selected product-ions together with the retention time, the identification is very selective and quantification is reliable. The method was successfully applied to real samples of membrane flushings, drinking water, surface waters and waste water. Additional investigations showed the instability of the isothiazolinones in river- and waste water. Preservation of river water and waste water samples with sodium azide (NaN₃) promotes the stability of the isothiazolines in solution. In membrane flushings, waste water, surface waters and drinking water, levels of the three isothiazolinones were all below the limit of detection. In effluents of households containing washings from normal shampoo use, isothiazolinones could be detected.     

Liquid chromatography–atmospheric pressure photoionization tandem mass spectrometry for analysis of 36 halogenated flame retardants in fish

A comprehensive, sensitive and high-throughput liquid chromatography–atmospheric pressure photoionization tandem mass spectrometry (LC–APPI-MS/MS) method has been developed for analysis of 36 halogenated flame retardants (HFRs). Under the optimized LC conditions, all of the HFRs eluted from the LC column within 14 min, while maintaining good chromatographic separation for the isomers. Introduction of the pre-heated dopant to the APPI source decreased the background noise fivefold, which enhanced sensitivity. An empirical equation was proposed to describe the relation between the ion intensity and dopant flow. The excellent on-column instrument detection limits averaged 4.7 pg, which was similar to the sensitivity offered by gas chromatography–high-resolution mass spectrometry (GC–HRMS). This method was used to analyze a series of fish samples. Good agreement was found between the results for PBDEs from LC–APPI-MS/MS and GC–HRMS.     

Qualitative and quantitative determination of complicated herbal components by liquid chromatography hybrid ion trap time-of-flight mass spectrometry and a relative exposure approach to herbal pharmacokinetics independent of standards

To date, the pharmacokinetic research of herbal medicines (HMs) is still in its infancy and is facing critical technical challenges on the qualitative and quantitative analysis of complicated components from biological matrices. Additionally, the lack of authentic standards constitutes another bottleneck on assessing herbal pharmacokinetics. This present work contributes to the development of a powerful technical platform for both qualitative and quantitative pharmacokinetic analysis of herbal components, and a strategy of relative exposure that provides a practicable pharmacokinetic assessment independent of authentic standards, based on the use of liquid chromatography hybrid ion trap time-of-flight mass spectrometry (LC–IT-TOF/MS). Taking schisandra lignans extract (SLE) as an example, the LC–IT-TOF/MS assay was initially applied to the global qualitative analysis of components contained in SLE per se and in the rat plasma post SLE dosing. Afterwards, this study focused on validating the quantitative performance of LC–IT-TOF/MS assay by comparison with a well-established LC–Q/MS assay. For the absolute quantification of five lignans components with authentic standards, both assays showed very similar analytical figures of merit such as linearity, precision, accuracy, and pharmacokinetic parameters. Compared with LC–Q/MS, the prominent advantage of LC–IT-TOF/MS assay is its much higher sensitivity. Moreover, a ‘relative exposure approach’ (REA) that entails the use of sequentially diluted original herbal preparations to prepare the ‘mixed calibration curves’ was developed to assessing herbal pharmacokinetics independent of specific authentic compounds for each component. Such an approach was found capable of providing virtually identical pharmacokinetic parameters as that from the typical pharmacokinetic assay calibrated by authentic standards, except for the absolute plasma concentrations. The presently developed methodology and approach will find its wide use in, but not limited to, the qualitative and quantitative pharmacokinetic analysis of herbal medicines.     

Analysis of trace levels of domoic acid in seawater and plankton by liquid chromatography without derivatization,using UV or mass spectrometry detection

Quantitation of trace levels of domoic acid (DA) in seawater samples usually requires labour-intensive protocols involving chemical derivatization with 9-fluorenylmethylchloroformate and liquid chromatography with fluorescence detection (FMOC–LC–FLD). Procedures based on LC–MS have been published, but time-consuming and costly solid-phase extraction pre-concentration steps are required to achieve suitable detection limits. This paper describes an alternative, simple and inexpensive LC method with ultraviolet detection (LC–UVD) for the routine analysis of trace levels of DA in seawater without the use of sample pre-concentration or derivatization steps. Qualitative confirmation of DA identity in dubious samples can be achieved by mass spectrometry (LC–MS) using the same chromatographic conditions. Addition of an ion-pairing/acidifying agent (0.15% trifluoroacetic acid) to sample extracts and the use of a gradient elution permitted the direct analysis of large sample volumes (100 μl), resulting in both high selectivity and sensitivity (limit of detection = 42 pg ml⁻¹ by LC–UVD and 15 pg ml⁻¹ by LC–MS). Same-day precision varied between 0.4 and 5%, depending on the detection method and DA concentration. Mean recoveries of spiked DA in seawater by LC–UVD were 98.8% at 0.1–10 ng ml⁻¹ and 99.8% at 50–1000 ng ml⁻¹. LC–UVD exhibited strong correlation with FMOC–LC–FLD during inter-laboratory analysis of Pseudo-nitzschia multiseries cultures containing 60–2000 ng DA ml⁻¹ (r² > 0.99), but more variable results were obtained by LC–MS (r² = 0.85). This new technique was used to confirm the presence of trace DA levels in low-toxicity Pseudo-nitzschia spp. isolates (0.2–1.6 ng ml⁻¹) and in whole-water field samples (0.3–5.8 ng ml⁻¹), even in the absence of detectable Pseudo-nitzschia spp. cells in the water column.     

Rapid confirmatory method for the determination of 11 nitroimidazoles in egg using liquid chromatography tandem mass spectrometry

A rapid confirmatory method has been developed and validated for the simultaneous identification, confirmation and quantitation of 11 nitroimidazoles in eggs by liquid chromatography tandem mass spectrometry (LC–MS/MS). The method is validated in accordance with Commission Decision 2002/657/EC and is capable of analysing metronidazole (MNZ), dimetridazole (DMZ), ronidazole (RNZ), ipronidazole (IPZ) and their hydroxy metabolites MNZ-OH, HMMNI (hydroxymethyl, methyl nitroimidazole), IPZ-OH. The method is also capable of analysing carnidazole (CRZ), ornidazole (ORZ), tinidazole (TNZ) and ternidazole (TRZ). MNZ, DMZ and RNZ have been assigned a recommended level (RL) of 3 μg kg⁻¹ by the Community Reference Laboratory (CRL) in Berlin. The developed method described in this study is easily able to detect all the nitroimidazole compounds investigated at this level and below. Egg samples are extracted with acetonitrile, and NaCl is added to help remove matrix contaminants. The acetonitrile extract undergoes a liquid–liquid wash step with hexane; it is then evaporated and reconstituted in mobile phase. The reconstituted samples are analysed by liquid chromatography tandem mass spectrometry (LC–MS/MS). The decision limits (CCα) range from 0.33 to 1.26 μg kg⁻¹ and the detection capabilities (CCβ), range from 0.56 to 2.15 μg kg⁻¹. The results of the inter-assay study, which was performed by fortifying hen egg samples (n = 18) on three separate days, show the accuracy calculated for the various analytes to range between 87.2 and 106.2%. The precision of the method, expressed as %CV values for the inter-assay variation of each analyte at the three levels of fortification (3, 4.5 and 6.0 μg kg⁻¹), ranged between 3.7 and 11.3%. A Day 4 analysis was carried out to examine species variances in eggs from different birds such as duck and quail and investigating differences in various battery and free range hen eggs.     

Dissipation of carbendazim and its metabolites in cucumber using liquid chromatography tandem mass spectrometry

Currently, there is growing interest in the degradation pathways of organic contaminants such as pesticides. In the case of pesticides, the determination of metabolites in agricultural products and environment is necessary as some of them could present similar toxicity to or even higher toxicity than the parent compound. The development of analytical methodology for the identification and quantification of carbendazim fungicide and its metabolites in cucumber was studied. Cucumber (cucumis sativus) is a global food in terms of economic importance and nutritional quality. Careful optimisation of the liquid chromatography–mass spectrometry (LC-MS)/MS parameters was achieved in order to attain a fast separation with the best sensitivity. The detection was carried out on an Ion-Trap tandem mass spectrometer (MS/MS) by electrospray ionisation in positive ion mode (ESI+) with multiple reaction monitoring (MRM).