Determination of multi-class pesticides in wines by solid-phase extraction and liquid chromatography-tandem mass spectrometry

This work reports a new sensitive multi-residue liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for detection, confirmation and quantification of forty-six pesticides and transformation products belonging to different chemical classes in wines. The proposed method makes use of a solid-phase extraction (SPE) procedure with Oasis HLB cartridges that combines isolation of the pesticides and sample clean-up in a single step. Analysis is performed by liquid chromatography-electrospray ionisation-tandem mass spectrometry (LC-MS/MS) operated in the selected reaction monitoring (SRM) mode, acquiring two specific precursor-product ion transitions per target compound. An investigation of matrix effects has been performed during method validation showing medium to low effects for the majority of the compounds. Limits of detection (LODs) were in the range 0.0003–0.003 mg L⁻¹ and limits of quantification (LOQs) were in the range 0.001–0.01 mg L⁻¹. The average recoveries, measured at two concentration levels (0.010 and 0.050 mg L⁻¹), were in the range 70–110% for most of the compounds tested with % relative standard deviations below 20%, while a value of 0.010 mg L⁻¹ has been established as the method limit of quantification (MLOQ) for all target species. Expanded uncertainty values were in the range 10–40% while the Horrat ratios were below 1. The method has been successfully applied to the analysis of 60 wine samples in the course of an annual monitoring study with carbendazim-benomyl, thiophanate-methyl and carbaryl being the most frequently determined pesticides.     

Detection of s-triazine pesticides in natural waters by modified large-volume direct injection HPLC

There is a need for simple and inexpensive methods to quantify potentially harmful persistent pesticides often found in our water-ways and water distribution systems. This paper presents a simple, relatively inexpensive method for the detection of a group of commonly used pesticides (atrazine, simazine and hexazinone) in natural waters using large-volume direct injection high performance liquid chromatography (HPLC) utilizing a monolithic column and a single wavelength ultraviolet-visible light (UV-vis) detector. The best results for this system were obtained with a mobile phase made up of acetonitrile and water in a 30:70 ratio, a flow rate of 2.0 mL min⁻¹, and a detector wavelength of 230 nm. Using this method, we achieved retention times of less than three minutes, and detection limits of 5.7 μg L⁻¹ for atrazine, 4.7 μg L⁻¹ for simazine and 4.0 μg L⁻¹ for hexazinone. The performance of this method was validated with an inter-laboratory trial against a National Association of Testing Authorities (NATA) accredited liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) method commonly used in commercial laboratories.     

Single solid phase extraction method for the simultaneous analysis of polar and non-polar pesticides in urine samples by gas chromatography and ultra high pressure liquid chromatography coupled to tandem mass spectrometry

A new multiresidue method has been developed and validated for the simultaneous extraction of more than two hundred pesticides, including non-polar and polar pesticides (carbamates, organochlorine, organophosphorous, pyrethroids, herbicides and insecticides) in urine at trace levels by gas and ultra high pressure liquid chromatography coupled to ion trap and triple quadrupole mass spectrometry, respectively (GC-IT-MS/MS, UHPLC-QqQ-MS/MS). Non-polar and polar pesticides were simultaneously extracted from urine samples by a simple and fast solid phase extraction (SPE) procedure using C₁₈ cartridges as sorbent, and dichloromethane as elution solvent. Recovery was in the range of 60-120%. Precision values expressed as relative standard deviation (RSD) were lower than 25%. Identification and confirmation of the compounds were performed by the use of retention time windows, comparison of spectra (GC-amenable compounds) or the estimation of the ion ratio (LC-amenable compounds). For GC-amenable pesticides, limits of detection (LODs) ranged from 0.001 to 0.436 μg L⁻¹ and limits of quantification (LOQs) from 0.003 to 1.452 μg L⁻¹. For LC-amenable pesticides, LODs ranged from 0.003 to 1.048 μg L⁻¹ and LOQs ranged from 0.011 to 3.494 μg L⁻¹. Finally, the optimized method was applied to the analysis of fourteen real samples of infants from agricultural population. Some pesticides such as methoxyfenozide, tebufenozide, piperonyl butoxide and propoxur were found at concentrations ranged from 1.61 to 24.4 μg L⁻¹, whereas methiocarb sulfoxide was detected at trace levels in two samples.     

An improved method for analyzing chlormequat and mepiquat in source waters by solid-phase extraction and liquid chromatography-mass spectrometry

A liquid chromatography-mass spectrometry (LC-MS) method for the identification and quantification of chlormequat (CQ) and mepiquat (MQ) in source waters with high sensitivity and specificity was established using WCX cartridges (150 mg/6 mL) for pre-concentration of the samples and using the CAPCELL PAK CR 1:4 (2.0 mm × 150 mm 5 μm, SCX:C18 = 1:4) column containing strong cationic exchange resins and C18 for separation. The method could solve the problem for pre-concentrating ionic compounds from water samples and avoid the MS instrument fouling problem accompanied with the use of ion-pair reagents. After the optimization of analytical conditions, quantification was achieved in the positive electrospray ionization mode using selected ion monitoring. The samples were analyzed with multi-channel mode with quantification performed at 30 V cone voltage to ascertain the sensitivity and qualitative analysis performed at 60 V cone voltage simultaneously. The method detection limits (MDLs) of CQ and MQ in source water were determined to be 14 and 22 ng L⁻¹. Finally, the method was used to quantify CQ and MQ in several source waters, which gave a level ranging from below the quantitation limit to 28 ng L⁻¹.     

High-performance liquid chromatography with paired ion electrospray ionization (PIESI) tandem mass spectrometry for the highly sensitive determination of acidic pesticides in water

A novel method based on the paired ion electrospray ionization (PIESI) mass spectrometry has been developed for determination of acidic pesticides at ultratrace levels in surface and ground waters. The proposed approach provides greatly enhanced sensitivity for acidic pesticides and overcomes the drawbacks of the less sensitive negative ion mode ESI-MS. The limits of detection (LODs) of 19 acidic pesticides were evaluated with four types of dicationic ion-pairing reagent (IPR) in both single ion monitoring (SIM) and selected reaction monitoring (SRM) mode. The LOD of 19 pesticides obtained with the use the optimal dicationic ion-pairing reagent ranged from 0.6 pg to 19 pg, indicating the superior sensitivity provided by this method. The transition pathways for different pesticide-IPR complexes during the collision induced dissociation (CID) were identified. To evaluate and eliminate any matrix effects and further decrease the detection limits, off-line solid-phase extraction (SPE) was performed for DI water and a river water matrix spiked with 2000 ng L⁻¹ and 20 ng L⁻¹ pesticides standards respectively, which showed an average percent recovery of 93%. The chromatographic separation of the acidic pesticides was conducted by high-performance liquid chromatography (HPLC) using a C18 column (250 mm × 2.1 mm) in the reversed phase mode using linear gradient elution. The optimized HPLC–PIESI-MS/MS method was utilized for determination of acidic pesticide at ng L⁻¹ level in stream/pond water samples. This experimental approach is 1–3 orders of magnitude more sensitive for these analytes than other reported methods performed in the negative ion mode.     

Measurement of trace levels of antibiotics in river water using on-line enrichment and triple-quadrupole LC-MS/MS

This study presents the development of an automated on-line solid phase extraction (SPE)-liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the determination of 23 antibiotics in environmental water samples. After optimisation of LC-MS/MS conditions, SPE parameters such as sorbent type, sample pH or sample volume were optimised. Antibiotic recoveries ranged from 64% to 98% and compared favourably with those achieved using off-line SPE. Limits of detection were in the range 0.5-13.7 ng L⁻¹.This on-line SPE-LC-MS/MS procedure was applied to the analysis of water samples taken in three rivers within the Seine River basin, near Paris (France). The obtained results revealed the occurrence of 12 antibiotics, including tylosin, erythromycin, tetracycline, amoxicillin, trimethoprim, sulfamethoxazole, oxolinic acid, flumequine, norfloxacin, ciprofloxacin, ofloxacin, and vancomycin (2-1435 ng L⁻¹).     

Multi-residue analysis of 30 currently used pesticides in fine airborne particulate matter (PM 2.5) by microwave-assisted extraction and liquid chromatography–tandem mass spectrometry

A confirmatory and rapid procedure has been developed for the determination of 30 currently used pesticides (CUP) in fine airborne particulate matter (PM 2.5) at trace level. The proposed method includes extraction of PM 2.5-bound pesticides by microwave-assisted extraction (MAE) followed by a direct injection into LC–MS/MS. The main parameters affecting the MAE extraction (time, temperature and volume of solvent) were optimised using statistical design of experiments (DoE). The matrix effect was also evaluated. Recoveries ranged from 72 to 109% and the limit of quantification (LoQ) was 32.5 pg m⁻³ for chlorpyrifos, 13.5 pg m⁻³ for fenhexamid, imazalil and prochloraz, and 6.5 pg m⁻³ for the rest of pesticides, when air volumes of 760 m³ were collected. The method was applied to 54 samples collected from three stations of the atmospheric monitoring network of the Regional Valencia Government (Spain) during April–July 2009. Nineteen out of 30 pesticides investigated were found in at least one sample: omethoate, carbendazim, acetamiprid, thiabendazole, malathion, flusilazole, metalaxyl, azoxystrobin, iprovalicarb, myclobutanil, tebuconazole, triflumizole, cyprodinil, tebufenpyrad, buprofezin, pyriproxyfen, hexythiazox, flufenoxuron and fenazaquin. The measured concentrations ranged from 6.5 to 1208 pg m⁻³. To our knowledge, 11 of the pesticides detected have been reported for the first time in ambient air.     

Multiresidue method for the determination of 13 pesticides in three environmental matrices: water, sediments and fish muscle

Pesticides residues in aquatic ecosystems are an environmental concern which requires efficient analytical methods. In this study, we proposed a generic method for the quantification of 13 pesticides (azoxystrobin, clomazone, diflufenican, dimethachlor, carbendazim, iprodion, isoproturon, mesosulfuron-methyl, metazachlor, napropamid, quizalofop and thifensulfuron-methyl) in three environmental matrices. Pesticides from water were extracted using a solid phase extraction system and a single solid-liquid extraction method was optimized for sediment and fish muscle, followed by a unique analysis by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). Limits of quantification were below 5 ng L⁻¹ for water (except for fluroxypyr and iprodion) and ranged between 0.1 ng g⁻¹ and 57.7 ng g⁻¹ for sediments and regarding fish, were below 1 ng g⁻¹ for 8 molecules and were determined between 5 and 49 ng g⁻¹ for the 5 other compounds. This method was finally used as a new routine practice for environmental research.     

A rapid determination of propiverine and its N-oxide metabolite in human plasma by high performance liquid chromatography-electrospray ionization tandem mass spectrometry

A simple, fast and sensitive high-performance liquid chromatography (HPLC)-electrospray ionization (ESI) tandem mass spectrometric method (LC-MS/MS) has been developed for determination of propiverine and propiverine N-oxide metabolite in human plasma using oxybutynin as internal standard. Instead of extracting propiverine from plasma using organic solvents, which should be separated from the aqueous phase and evaporated before injecting the sample into the chromatograph, plasma sample containing propiverine and N-oxide was directly injected after precipitating proteins with acetonitrile. Numerous compounds in the plasma did not interfere with the highly specific multiple reaction monitoring in tandem mass spectrometric detection following C₈ reversed-phase chromatographic separation under conditions that eluted propiverine, N-oxide and oxybutynin within 2 min (0.1% formic acid in water/acetonitrile, 25:75, v/v). The LC-MS/MS method and an alternative LC-MS method, using methyl-t-butyl ether extraction and selected ion monitoring, were validated over 1-250 ng ml⁻¹ of propiverine and 2 to 500 ng ml⁻¹ of N-oxide, and successfully applied in a pharmacokinetic study. The lower limit of quantitation was 1 ng ml⁻¹ for propiverine and 2 ng ml⁻¹ for N-oxide in both methods.     

A new liquid chromatography-tandem mass spectrometry method for determination of parabens in human placental tissue samples

Endocrine disruptors are a group of organic compounds widely used, which are ubiquitous in the environment and in biological samples. The main effect of these compounds is associated with their ability to mimic or block the action of natural hormones in living organisms, including humans. Parabens (esters of p-hydroxybenzoic acid) belong to this group of compounds. In this work, we propose a new liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to asses the presence of parabens most commonly used in industrial applications (methyl-, ethyl-, propyl- and butyl-paraben) in samples of human placental tissue. The method involves the extraction of the analytes from the samples using ethyl acetate, followed by a clean-up step using centrifugation prior to their quantification by LC-MS/MS using an atmospheric pressure chemical ionization (APCI) interface in the negative mode. Deuterated bisphenol A (BPA-d₁₆) was used as surrogate. Found detection limits (LOD) ranged from 0.03 to 0.06 ng g⁻¹ and quantification limits (LOQ) from 0.1 to 0.2 ng g⁻¹, while inter- and intra-day variability was under 13.8%. The method was validated using standard addition calibration and a spike recovery assay. Recovery rates for spiked samples ranged from 82% to 108%. This method was satisfactorily applied for the determination of parabens in 50 placental tissue samples collected from women who live in the province of Granada (Spain).     

Stereoselective quantitation of mecoprop and dichlorprop in natural waters by supramolecular solvent-based microextraction,chiral liquid chromatography and tandem mass spectrometry

Liquid chromatography (LC)/tandem mass spectrometry (MS/MS) after supramolecular solvent-based microextraction (SUSME) was firstly used in this work for the enantioselective determination of chiral pesticides in natural waters. The method developed for the quantitation of the R- and S-enantiomers of mecoprop (MCPP) and dichlorprop (DCPP) involved the extraction of the herbicides in a supramolecular solvent (SUPRAS) made up of reverse aggregates of dodecanoic acid (DoA), analyte re-extraction in acetate buffer (pH = 5.0), separation of the target enantiomers on a chiral column of permethylated α-cyclodextrin under isocratic conditions, and detection of the daughter ions (m/z = 140.9 and 160.6 for MCPP and DCPP, respectively) using a hybrid triple quadrupole mass spectrometer equipped with an electrospray source operating in the negative ion mode. Similar recoveries (ca. 75%) and actual concentration factors (ca. 94) were obtained for both phenoxypropanoic acids (PPAs). The quantitation limits were 1 ng L⁻¹ for R- and S-MCPP, and 4 ng L⁻¹ for R- and S-DCPP, and the precision, expressed as relative standard deviation (n = 6) was in the ranges 2.4–2.7% ([R-MCPP] = [S-MCPP] = 5 ng L⁻¹ and [R-DCPP] = [S-DCPP] = 15 ng L⁻¹) and 1.6–1.8% (100 ng L⁻¹ of each enantiomer). The SUSME-LC–MS/MS method was successfully applied to the determination of the enantiomers of MCPP and DCPP in river and underground waters, fortified at concentrations between 15 and 180 ng L⁻¹ at variable enantiomeric ratios (ER = 1–9).     

Determination of benzophenones in human placental tissue samples by liquid chromatography-tandem mass spectrometry

Benzophenones (BPs) are a family of compounds widely used to protect the skin and hair from UV irradiation. Despite human exposure to BPs through dermal application of products containing sunscreen agents and the increasing evidence that BPs are able to interfere with endocrine systems, few studies have examined the occurrence of BPs in humans. In this work, we propose a new liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to determine six BPs, namely, benzophenone-1 (BP-1), benzophenone-2 (BP-2), benzophenone-3 (BP-3), benzophenone-6 (BP-6), benzophenone-8 (BP-8) and 4-hydroxybenzophenone (4-OH-BP) in human placental tissue samples. The method involves an extraction step of the analytes from the samples using ethyl acetate, followed by a clean-up step using centrifugation prior to their quantification by LC-MS/MS using an atmospheric pressure chemical ionization (APCI) interface in the positive mode. Benzophenone-d₁₀ (BP-d₁₀) was used as surrogate. Found detection limits (LOD) ranged from 0.07 to 0.3 ng g⁻¹ and quantification limits (LOQ) from 0.3 to 1.0 ng g⁻¹, while inter- and intra-day variability was under 5%. The method was validated using standard addition calibration and a recovery assay. Recovery rates for spiked samples ranged from 98 to 104%. This method was satisfactorily applied for the determination of BPs in 16 placental tissue samples collected from women who live in Granada (Spain).     

Development and validation of a multi-residue method for the determination of pesticides in honeybees using acetonitrile-based extraction and gas chromatography–tandem quadrupole mass spectrometry

An optimized analytical method employing gas chromatography–tandem quadrupole mass spectrometry (GC–MS/MS) has been developed for the simultaneous screening of roughly 150 pesticides in honeybees suspected of poisoning by pesticides during field spraying. In this work, a sample preparation approach based on acetonitrile extraction followed by dispersive solid-phase extraction (d-SPE) cleanup was implemented and validated for pesticides in honeybees for the first time. The procedure involved homogenization of a 2 g sample (23 insects on average) with acetonitrile–water mixture followed by salting out with citrate buffer, magnesium sulphate and sodium chloride. An amount of matrix constituents with limited solubility in acetonitrile was reduced in the extract by precipitation at low-temperature (freezing-out cleanup). Hereafter, d-SPE cleanup was carried out using primary secondary amine (PSA), octadecyl (C18) and graphitized carbon black (GCB). This combination of cleanup steps ensured efficient extract purification. Linearity of the calibration curves was studied using matrix-matched standards in the concentration range between 4 and 500 ng mL⁻¹ (equivalent to 10 and 1250 ng g⁻¹), and coefficients of determination (R²) were ≥0.99 for approximately 90% of the targeted compounds. The recovery data were obtained by spiking honeybees samples free of pesticides at three concentration levels of 10, 50, and 500 ng g⁻¹ (approximately 0.9, 4.3, 43.5 ng per bee). At these spiking levels 47, 77 and 92% of the targeted compounds were recovered, respectively. Generally the recoveries were in the range between 70 and 120% with precision values, expressed as relative standard deviation (RSD) ≤ 20%. The expanded uncertainty was estimated following a “top down” empirical model as being 28% on average (coverage factor k = 2, confidence level 95%). Preliminary results from practical application to analysis of real samples are presented. A total of 25 samples of honeybees from suspected pesticides poisoning incidents were analyzed, in which 10 different pesticides were determined.     

Multiresidue analytical methods for the ultra-trace quantification of 33 priority substances present in the list of REACH in real water samples

Innovative and simultaneous multiresidue analytical methods of 33 multi-class pollutants in wastewaters, surface and ground waters, using solid phase extraction (SPE) followed by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) are presented. Target compounds include several groups of emerging and persistent contaminants derived from the European priority list of the registration evaluation and authorisation of chemicals system (REACH): organochlorine (8) and organophosphorus (2) pesticides, carbamates (2), fungicides (8), phthalates (2), alkylphenols (10) and bisphenol A.The recovery rates of the SPE gave levels ranged from 84 to 118% with exception of some compounds that yielded lower (methamidophos (50%), p,p′-DDT (60%) and o,p′-DDT (72%)) but all recoveries were acceptable. Low limits of detection (LOD) varied between 0.2 and 88.9 ng L⁻¹ (except for HPTE and 4n-octylphenol giving 161 and 220 ng L⁻¹, respectively). A study of matrix effects was performed in order to evaluate the best and reliable calibration approach.The developed analytical method was successfully applied to the analysis of the 33 substances in wastewater effluents as well as surface and ground waters. The most frequently detected families were alkylphenols and industrial endocrine disrupting compounds (phthalates and bisphenol A).     

Validation of method for determination of different classes of pesticides in aqueous samples by dispersive liquid-liquid microextraction with liquid chromatography-tandem mass spectrometric detection

In this study, a simple, rapid and efficient method has been developed for the extraction and preconcentration of different classes of pesticides, carbofuran (insecticide), clomazone (herbicide) and tebuconazole (fungicide) in aqueous samples by dispersive liquid-liquid microextraction (DLLME) coupled with liquid chromatography-tandem mass spectrometric detection. Some experimental parameters that influence the extraction efficiency, such as the type and volume of the disperser solvents and extraction solvents, extraction time, speed of centrifugation, pH and addition of salt were examined and optimized. Under the optimum conditions, the recoveries of pesticides in water at spiking levels between 0.02 and 2.0 μg L⁻¹ ranged from 62.7% to 120.0%. The relative standard deviations varied between 1.9% and 9.1% (n = 3). The limits of quantification of the method considering a 50-fold preconcentration step were 0.02 μg L⁻¹. The linearity of the method ranged from 1.0 to 1000 μg L⁻¹ for all compounds, with correlation coefficients varying from 0.9982 to 0.9992. Results show that the method we propose can meet the requirements for the determination of pesticides in water samples. The comparison of this method with solid-phase extraction indicates that DLLME is a simple, fast, and low-cost method for the determination of pesticides in natural waters.     

Validation of an enzyme-linked immunosorbent assay (ELISA) for the determination of 4-nonylphenol and octylphenol in surface water samples by LC-ESI-MS

4-Nonylphenol (NP) and octylphenol (OP) were measured by direct ELISA in both laboratory-fortified and surface water samples collected monthly from 10 rivers. In this procedure, samples were concentrated by solid phase extraction (SPE) using Lichrolut RP-18 sorbent with good recoveries obtained for both LC-MS and ELISA, giving a low level of detection (LOD) at the range of low μg L⁻¹ and good reproducibility. Analysis of 40 surface water samples demonstrated that the ELISA may be a useful screening tool for the determination of the alkylphenols in surface water matrices. The concentration of NP and OP in surface waters ranged from 0.11 to 6.58 μg L⁻¹. A good correlation of results obtained by ELISA and LC-MS within the concentration range of 0.08-6.86 μg L⁻¹ was found in the river samples [R² = 0.924, n = 39]. The influence of various factors on assay determination was also discussed.     

Multi-class,multi-residue analysis of pesticides,polychlorinated biphenyls,polycyclic aromatic hydrocarbons,polybrominated diphenyl ethers and novel flame retardants in fish using fast,low-pressure gas chromatography–tandem mass spectrometry

A multi-class, multi-residue method for the analysis of 13 novel flame retardants, 18 representative pesticides, 14 polychlorinated biphenyl (PCB) congeners, 16 polycyclic aromatic hydrocarbons (PAHs), and 7 polybrominated diphenyl ether (PBDE) congeners in catfish muscle was developed and evaluated using fast low pressure gas chromatography triple quadrupole tandem mass spectrometry (LP-GC/MS–MS). The method was based on a QuEChERS (quick, easy, cheap, effective, rugged, safe) extraction with acetonitrile and dispersive solid-phase extraction (d-SPE) clean-up with zirconium-based sorbent prior to LP-GC/MS–MS analysis. The developed method was evaluated at 4 spiking levels and further validated by analysis of NIST Standard Reference Materials (SRMs) 1974B and 1947. Sample preparation for a batch of 10 homogenized samples took about 1 h/analyst, and LP-GC/MS–MS analysis provided fast separation of multiple analytes within 9 min achieving high throughput. With the use of isotopically labeled internal standards, recoveries of all but one analyte were between 70 and 120% with relative standard deviations less than 20% (n = 5). The measured values for both SRMs agreed with certified/reference values (72–119% accuracy) for the majority of analytes. The detection limits were 0.1–0.5 ng g⁻¹ for PCBs, 0.5–10 ng g⁻¹ for PBDEs, 0.5–5 ng g⁻¹ for select pesticides and PAHs and 1–10 ng g⁻¹ for flame retardants. The developed method was successfully applied for analysis of catfish samples from the market.     

Determination of perfluorooctanoic acid and perfluorooctane sulfonate by automated in-tube solid-phase microextraction coupled with liquid chromatography-mass spectrometry

We have developed a simple, rapid, and sensitive method for the determination of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) by on-line in-tube solid-phase microextraction (SPME) coupled with liquid chromatography-mass spectrometry (LC-MS). PFOA and PFOS were separated within 10 min by high-performance liquid chromatography using an Inertsil ODS-3 column and 10 mM ammonium acetate/methanol (35/65, v/v) as a mobile phase at a flow rate of 0.25 mL min⁻¹. Electrospray ionization conditions in the negative ion mode were optimized for MS detection of PFOA and PFOS. The optimum in-tube SPME conditions were 20 draw/eject cycles with a sample size of 40 μL using a CP-Pora PLOT amine capillary column as the extraction device. The extracted compounds could be desorbed easily from the capillary by passage of the mobile phase, and no carryover was observed. Using the in-tube SPME LC-MS method, good linearity of the calibration curve (r = 0.9990 for PFOA, r = 0.9982 for PFOS) was obtained in the range of 0.05-5 ng mL⁻¹ each compound. The detection limits (S/N = 3) for PFOA and PFOS were 1.5 and 3.2 pg mL⁻¹, respectively. The method described here showed about 100-fold higher sensitivity than the direct injection method. The within-day and between-day precisions (relative standard deviations) were below 3.7 and 6.0%, respectively. This method was applied successfully to the analysis of PFOA and PFOS in environmental water samples and to the elution test from a Teflon^®-coated frying pan without interference peaks. The recoveries of PFOA and PFOS spiked into river samples were above 81%, and PFOA was detected at pg mL⁻¹ levels in environmental water samples and eluate from the frying pan.     

Quantitative metabolic profiling of 21 endogenous corticosteroids in urine by liquid chromatography-triple quadrupole-mass spectrometry

Since corticosteroid metabolism may be affected by disease states, the accurate and precise measurement of endogenous corticosteroids in urine is necessary to understand their biochemical roles. An efficient quantitative profiling of 21 endogenous corticosteroids in urine has been validated by liquid chromatography-tandem mass spectrometry (LC-MS/MS). After enzymatic hydrolysis with β-glucuronidase, samples were purified using a solid-phase extraction cartridge and then separated through a sub-2 μm particle C18 column (2.1 mm × 50 mm, 1.9 μm) and quantified within 12.1 min using a triple quadrupole MS with electrospray ionization in positive ion mode. All corticosteroids resulted in the base-line separation, which is even achieved for stereo-isomers, such as α-/β-cortol, α-/β-cortolone, and allo-tetrahydrocortisol/tetrahydrocortisol. Overall recoveries ranged from 85% to 106% with limit of quantification ranged from 0.5 to 2.0 ng mL⁻¹ for the corticosteroids examined. The precision (% CV) and accuracy (% bias) of the assay were 1.7-7.8% and 95.1-105.4%, respectively, in 0.5-200 ng mL⁻¹ calibration ranges (r² > 0.9903), for quality-control samples containing 21 endogenous corticosteroids at three different urinary concentrations. Clinical application included quantitative analysis from patients with both prostate cancer and benign prostatic hyperplasia with altered cortisol concentrations. The described LC-MS/MS method eliminates interference from other urine components, has excellent chromatographic resolution achieved by a small particle LC column with a sufficient sensitivity to allow the profiling of both gluco- and mineralo-corticosteroids at a time.     

Validation of a qualitative screening method for pesticides in fruits and vegetables by gas chromatography quadrupole-time of flight mass spectrometry with atmospheric pressure chemical ionization

A wide-scope screening method was developed for the detection of pesticides in fruit and vegetables. The method was based on gas chromatography coupled to a hybrid quadrupole time-of-flight mass spectrometer with an atmospheric pressure chemical ionization source (GC-(APCI)QTOF MS). A non-target acquisition was performed through two alternating scan events: one at low collision energy and another at a higher collision energy ramp (MS^E). In this way, both protonated molecule and/or molecular ion together with fragment ions were obtained in a single run. Validation was performed according to SANCO/12571/2013 by analysing 20 samples (10 different commodities in duplicate), fortified with a test set of 132 pesticides at 0.01, 0.05 and 0.20 mg kg⁻¹. For screening, the detection was based on one diagnostic ion (in most cases the protonated molecule). Overall, at the 0.01 mg kg⁻¹ level, 89% of the 2620 fortifications made were detected. The screening detection limit for individual pesticides was 0.01 mg kg⁻¹ for 77% of the pesticides investigated. The possibilities for identification according to the SANCO criteria, requiring two ions with a mass accuracy ≤±5 ppm and an ion-ratio deviation ≤±30%, were investigated. At the 0.01 mg kg⁻¹ level, identification was possible for 70% of the pesticides detected during screening. This increased to 87% and 93% at the 0.05 and 0.20 mg kg⁻¹ level, respectively. Insufficient sensitivity for the second ion was the main reason for the inability to identify detected pesticides, followed by deviations in mass accuracy and ion ratios.