Selected Ion Monitoring Acquisition Research Articles

WTV2.0: A high-coverage plant volatilomics method with a comprehensive selective ion monitoring acquisition mode

Volatilomics is essential for understanding the biological functions and fragrance contributions of plant volatiles. However, the annotation coverage achieved using current untargeted and widely targeted volatomics (WTV) methods has been limited by low sensitivity and/or low acquisition coverage. Here, we introduce WTV 2.0, which enabled the construction of a high-coverage library containing 2111 plant volatiles, and report the development of a comprehensive selective ion monitoring (cSIM) acquisition method, including the selection of characteristic qualitative ions with the minimal ion number for each compound and an optimized segmentation method, that can acquire the smallest but sufficient number of ions for most plant volatiles, as well as the automatic qualitative and semi-quantitative analysis of cSIM data. Importantly, the library and acquisition method we developed can be self-expanded by incorporating compounds not present in the library, utilizing the obtained cSIM data. We showed that WTV 2.0 increases the median signal-to-noise ratio by 7.6-fold compared with the untargeted method, doubled the annotation coverage compared with the untargeted and WTV 1.0 methods in tomato fruit, and led to the discovery of menthofuran as a novel flavor compound in passion fruit. WTV 2.0 is a Python library with a user-friendly interface and is applicable to profiling of volatiles and primary metabolites in any species.

Low‐level determination of 4‐chlorobutyl‐(S)‐[4‐chloro‐2‐(4‐cyclopropyl‐1,1,1‐trifluoro‐2‐hydroxy‐but‐3yn‐2‐yl)phenyl] carbamate (4‐CTHC) in efavirenz drug substance by LC–MS

A rapid, simple, sensitive, and selective liquid chromatography-tandem mass spectrometry (LC-MS) test method was developed and validated for the trace level determination of 4-chlorobutyl-(S)-[4-chloro-2-(4-cyclopropyl-1,1,1-trifluoro-2-hydroxy-but-3yn-2-yl)phenyl] carbamate (4-CTHC). 4-CTHC is a potential genotoxic impurity in efavirenz drug substance and the acceptable level is 2.5 μg ml-1 with respect to analyte concentration according to ICH M7(R1) Multidisciplinary Guidelines M7(R1). The LC-MS/MS analysis of 4-CTHC impurity was carried out on a Kinetex C18 (150 × 4.6 mm, 5.0 μm) column. In this test procedure, the mobile phase was prepared with buffer (0.1% formic acid in water) and acetonitrile in the ratio of 1:3 (v/v). The method set flow rate was 0.4 ml min-1 . The method was developed with a short run time of <10 min. Selective ion monitoring acquisition mode and negative polarity electrospray ionization mode were used as an MS method to quantify genotoxic impurities at 422.25 Da. The method showed linearity in a range of 0.64-3.71 μg ml-1 with a correlation coefficient of 0.9992. The RSD for intra-day and inter-day precision was found to be <5%. The method's accuracy was in the range of 106.5-112.4% for the genotoxic impurity of 4-CTHC. The procedure was validated as per the current ICH Q2 (R1) guidelines and proved suitable for stability testing in the quality control laboratory for pharmaceutical preparations.

High throughput bar adsorptive microextraction: A simple and effective analytical approach for the determination of nicotine and cotinine in urine samples

A simple, effective, convenient and environmentally friendly methodology using high throughput bar adsorptive microextraction (HT-BAμE) with microliquid desorption in combination with large volume injection-gas chromatography-mass spectrometry operating in the selected-ion monitoring acquisition mode (LVI–GC–MS(SIM)) was applied for the determination of nicotine and cotinine in urine samples. Under optimized experimental conditions, the developed methodology allowed for linear dynamic ranges between 20.0 and 2000.0 μg L-1 with determination coefficients of 0.9991 and 0.9992, as well as average recovery yields of 61.7–67.5% and 53.9–57.8% for nicotine and cotine, respectively. The developed methodology was applied to monitor urine samples from 86 volunteers having different smoking habits, where nicotine and cotinine were quantified in the range from 23.6 to 2612.6 μg L-1.The target compounds were extracted in a HT-BAμE apparatus, which allows for simultaneous microextraction and subsequent back-extraction of up to 100 samples. This is a major improvement over other microextraction techniques.The data from the proposed methodology were satisfactory and in line with current green analytical chemistry guidelines, and proved to be an effective sample preparation alternative with substantial potential for high throughput bioanalysis.

Monitoring traces of organochlorine pesticides in herbal matrices by bar adsorptive microextraction – Application to black tea and tobacco

ABSTRACT Bar adsorptive microextraction followed by microliquid desorption and gas chromatography-mass spectrometry, under the selected ion monitoring acquisition mode, has been developed for the determination of 20 organochlorine pesticides (OCPs) in herbal matrices. Assays performed on 25 mL of ultra-pure water samples spiked at the 2.0 µg L−1 level, yielded average recoveries ranging from 14.0% to 95.1% for the target OCPs, under optimised experimental conditions. The proposed analytical methodology demonstrated suitable detection limits (0.10–0.15 µg L−1) and good linear dynamic ranges (0.5–100.0 µg L−1) with determination coefficients equal or higher than 0.9900. The proposed methodology, by using the standard addition method, proved to be a suitable sorption-based static microextraction alternative to monitor traces of OCPs in black tea and tobacco products, in compliance with the green analytical chemistry principles.

Dual-hollow fiber microextraction (dual-HFμE) - application for monitoring trace levels of organochlorine pesticides in real matrices

ABSTRACT In this contribution, the features and the advantages of the modified hollow fibre microextraction (HFµE) technique are discussed, by using two membranes (dual-HFµE) per sample, loaded with convenient organic solvents. The new approach proposed combined with micro-liquid desorption followed by large volume injection-gas chromatography-mass spectrometry operating in the selected-ion monitoring acquisition mode, [dual-HFμE-μLD/LVI-GC-MS(SIM)], was applied for trace analysis of 17 organochlorine pesticides (OCPs) in real matrices. By using dual-HFµE devices embedded with n-heptane and toluene (≈ 50 µL), fast kinetics (2 h) and selectivity enhancement were achieved to monitor 17 OCPs, particularly for the benzene hexachlorides, with convenient precision (RSD < 16%). Assays performed on 25 mL aqueous samples spiked with OCPs at the trace level yielded average recoveries between (40.6 ± 6.8) % and (101.7 ± 8.0) %, low detection limits (0.01–0.02 µg L−1), as well as good linear dynamic ranges (0.07–10.00 µg L−1) with suitable determination coefficients (r 2 > 0.9941). Through the standard addition method, the proposed methodology demonstrated good performance to monitor OCPs at the trace level in several types of matrices, including tap water, wastewater, soil, tea, and tomato samples. Besides the performance obtained and the wide applicability demonstrated, the dual-HFμE technique proved to be user-friendly, eco-friendly, cost-effective, and very competitive for routine work, being a remarkable alternative over other well-established microextraction techniques for trace analysis of priority and emerging compounds in real matrices.

Application of Gas Chromatography Coupled to Quadrupole-Orbitrap Mass Spectrometry for Pesticide Residue Analysis in Cereals and Feed Ingredients.

A method for residue analysis of pesticides and polychlorinated biphenyls in cereals and feed ingredients based on QuEChERS extraction, programmed temperature vaporizer large-volume injection, and GC with electron ionization (EI) quadrupole Orbitrap full-scan high-resolution MS (60 000 full width at half-maximum at m/z 200) has been developed. In addition to full-scan acquisition, simultaneous full-scan and selected-ion monitoring acquisition was used to improve detectability in incidental cases in which analytes coeluted with intense signals from coextractants. The method was successfully validated down to 10 µg/kg for a single commodity (wheat) using matrix-matched calibration, and for multiple-feed matrixes using standard addition. Identification according to European Union requirements was achieved in >90% of the analyte/matrix combinations, and suggestions for further increasing identification rates have been made. Performance characteristics were compared to an existing method for residue analysis based on GC with EI tandem MS (triple quadrupole).

On-line coupling of solid-phase extraction to gas chromatography–mass spectrometry to determine musk fragrances in wastewater

An on-line coupling solid-phase extraction (SPE) has been developed for the first time to preconcentrate trace amounts of 17 musk fragrances extensively used in personal care products (6 polycyclic musks, 3 nitro musks, 7 macrocyclic musks and 1 polycyclic musk degradation product) from wastewater samples, prior to analysis by gas chromatography and mass spectrometry through an on-column interface. A 10mm×2mm I.D. precolumn packed with Oasis HLB (60μm) or C18 (60μm) was compared for the optimization of the solid-phase extraction process. The parameters affecting the transfer of the analytes from the precolumn to the GC system (e.g. flow-rate, temperature and solvent vapor exit time) as well as SPE parameters (e.g. sample flow, sample volume, elution solvent, etc.) were optimized. An organic modifier such as methanol was added to the sample before the extraction process to avoid adsorption problems. The use of the MS detector under selected ion monitoring acquisition enabled the analytes to be quantified at low ngL−1 levels, preconcentrating only 10mL of sample, and the limits of detection were between 1 and 30ngL−1. The method was applied for the determination of musk fragrances in wastewater samples from three urban wastewater treatment plants (WWTPs). The analysis of influent urban wastewater revealed that galaxolide, tonalide and ambrettolide were the most abundant musk compounds with concentrations ranging between 18ngL−1 and 45,091ngL−1, 852ngL−1 and 49,904ngL−1 and 507ngL−1 and 21,528ngL−1 respectively. The remaining musks were present at lower concentrations and two of the macrocyclic musk studied (musk MC4 and civetone) were not detected. The analysis of effluent wastewater showed a decrease in the concentrations of all of the compounds present in influent samples, with the decrease being more significantly in the case of polycyclic and nitro musks than for macrocyclic musks. Only HHCB-lactone remained constant or increased its concentration.

Determination of endosulfan isomers and their metabolites in tap water and commercial samples using microextraction by packed sorbent and GC–MS

A simple, rapid, accurate and sensitive method using microextraction by packed sorbent (MEPS) followed by GC-MS has been pursued for the determination of organochlorine insecticide endosulfan isomers (α and β) and their metabolites (ether, lactone and sulfate). MEPS is a miniaturised version of SPE employing C18 packing material. It is very efficient technique as it employs as low as 10 μL of sample volume. The distinct feature of MEPS is the magnitude of the elution volume that could be directly injected to GC system. Various parameters such as extraction cycles, washing solvent, elution solvent, elution volume and pH, which influenced the MEPS performance, were tested and optimised. The calibration curves were obtained in the concentration range 1-500 ng/mL. The results showed a close correlation coefficient (R(2) > 0.991) for all analytes in the calibration range studied. The LOD and LOQ obtained for GC-MS under selected ion monitoring acquisition are between 0.0038-0.01 and 0.0125-0.033 ng/mL, respectively. The developed method is applicable for the quantification of these compounds in tap water and commercial samples. This method has been shown to be selective as no interferences from endogenous substances were detected by analysis. This method not only decreases sample preparation time but is cheaper, eco-friendly and easier to perform compared to traditional techniques.

Effects of ultrasonic irradiation and direct heating on extraction of priority pesticides from marine sediments

Priority pesticides (alachlor, aldrin, γ-chlordane, chlorfenvinphos, chlorpyrifos, dieldrin, 4,4′-DDT, 4,4′-DDD, 4,4′-DDE, α-endosulfan, β-endosulfan, endosulfan sulphate, endrin, α-HCH, β-HCH, γ-HCH, δ-HCH, HCB, HCBD, heptachlor, heptachlor epoxide, isodrin, methoxychlor, mirex, quintozene, terbuthylazine and trifluralin) are a group of toxic substances that are known by their persistency in the aquatic environment. Their screening in marine sediments may provide information on the sources and distribution in the water mass of fresh-transitional and coastal waters. This work proposes a rapid and reliable method to extract multi-residues of priority pesticides by ultrasounds irradiation from marine sediments. Multiple variables have been optimised: ultrasound frequency, sonication intensity, signal operation mode, time of extraction and water bath temperature. After sample clean-up and pre-concentration of the pesticides by stir bar sorptive extraction, the compounds were analysed by gas chromatography-mass spectrometry (GC-MS) using the selective ion monitoring acquisition mode (SIM). Better performance was found for ultrasonic-assisted extractions (UAE) at frequency of 35 kHz and an output intensity of 60% in a sweep mode of operation. An increase of water bath temperature to 80°C had a significant effect on the extraction of pesticides with high octanol-water partitioning coefficients (Kow). Under optimal conditions, method detection limits (MDLs) and method quantification limits (MQLs) ranged from 0.3 to 4.4 ng g−1 and from 0.8 to 14 ng g−1, respectively. Recoveries between 70 and 111%, at high precision levels, were found at different types of marine sediments with a single extraction cycle. Method performance was in good agreement with quality control guidelines.

Improvements on bar adsorptive microextraction (BAμE) technique–Application for the determination of insecticide repellents in environmental water matrices

Bar adsorptive microextraction combined with micro-liquid desorption followed by large volume injection-gas chromatography-mass spectrometry operating in the selected-ion monitoring acquisition mode (BAµE-µLD/LVI-GC-MS(SIM)), is proposed for the determination of trace levels of three insecticide repellents (N,N-diethyl-meta-toluamide (DEET), cis and trans permethrin (PERM)) in environmental water matrices. By comparing different sorbent coatings (five activated carbons and six polymers) through BAµE, an activated carbon (AC2) proved to be the best compromise between selectivity and efficiency, even against polydimethylsiloxane through stir bar sorptive extraction. The novel improvement proposed on the back-extraction stage performed in a single step, by reducing the desorption solvent volume at the microliter level, demonstrated remarkable performance turning possible to save time, making easier the practical manipulation and more environmentally friendly. Assays performed by BAµE(AC2)-µLD/LVI-GC-MS(SIM) on 25 mL of ultrapure water samples spiked at the 1.0 μg/L level, yielded recoveries ranging from 73.8±8.8% (trans-PERM) to 96.4±9.9% (DEET), under optimised experimental conditions. The analytical performance showed convenient detection limits (8-20 ng/L) and good linear dynamic ranges (0.04-4.0 µg/L) with suitable determination coefficients (r(2)>0.9963, DEET). Excellent repeatability were also achieved through intraday (RSD<14.9%) and interday (RSD<11.9%) experiments. The novel improvement on downsizing the BAµE device to half-size proved to be either a promising option in forthcoming to reduce still more the desorption solvent volume without losing microextraction efficiency. By using the standard addition methodology, the application of the present analytical approach on tap, ground, river, swimming-pool and estuary water samples revealed good sensitivity at trace level and absence of matrix effects.

Comparison of the selectivity of different sorbent phases for bar adsorptive microextraction—Application to trace level analysis of fungicides in real matrices

Bar adsorptive micro-extraction combined with liquid desorption followed by large volume injection–gas chromatography–mass spectrometry operating in the selected-ion monitoring acquisition mode (BAμE–LD/LVI–GC–MS(SIM)) was developed for the determination of trace levels of ten fungicides (azoxystrobin, difenoconazole, metalaxyl-M, myclobutanil, penconazole, tebuconazole, flusilazole, cyprodinil, procymidone and benalaxyl) in aqueous matrices. By comparing different sorbent coatings (two activated carbons, two styrene–divinylbenzene and one modified pyrrolidone polymers) through BAμE, the latter phase showed much higher selectivity and capacity offering multiple mechanisms of interaction, even against polydimethylsiloxane by stir bar sorptive extraction. Assays performed on 25mL of water samples spiked at the 0.8μg/L level, yielded recoveries ranging from 100.0 to 107.8%, under optimized experimental conditions; BAμE(modified pyrrolidone) – equilibrium time: 4h (1000rpm), pH 5.5; LD – solvent:methanol/acetonitrile (1/1), 15min with sonification. The analytical performance showed convenient detection limits (4.0–30.0ng/L) and excellent linear dynamic ranges (0.04–1.60μg/L) with remarkable correlation coefficients (r2>0.9980). Excellent repeatability was also achieved through intraday (RSD<13.7%) and interday (RSD<9.9%) assays. By using the standard addition methodology, the application of the present analytical approach on tap and ground water, as well as, wine samples revealed good sensitivity and absence of matrix effects. The proposed method operating under floating sampling technology proved to be a suitable sorption-based static microextraction alternative to monitor fungicides in real matrices, showing to be easy to implement, reliable, sensitive, requiring low sample volume and the possibility to choose the most selective sorbent coating according to the targets of interest.

Stir-bar-sorptive extraction and liquid desorption combined with large-volume injection gas chromatography–mass spectrometry for ultra-trace analysis of musk compounds in environmental water matrices

Stir-bar-sorptive extraction with liquid desorption followed by large-volume injection and capillary gas chromatography coupled to mass spectrometry in selected ion monitoring acquisition mode (SBSE-LD/LVI-GC-MS(SIM)) has been developed to monitor ultra-traces of four musks (celestolide (ADBI), galaxolide (HHCB), tonalide (AHTN) and musk ketone (MK)) in environmental water matrices. Instrumental calibration (LVI-GC-MS(SIM)) and experimental conditions that could affect the SBSE-LD efficiency are discussed. Assays performed on 30-mL water samples spiked at 200 ng L(-1) under optimized experimental conditions yielded recoveries ranging from 83.7 ± 8.1% (MK) to 107.6 ± 10.8% (HHCB). Furthermore, the experimental data were in very good agreement with predicted theoretical equilibria described by octanol-water partition coefficients (K (PDMS/W) ≈ K (O/W)). The methodology also showed excellent linear dynamic ranges for the four musks studied, with correlation coefficients higher than 0.9961, limits of detection and quantification between 12 and 19 ng L(-1) and between 41 and 62 ng L(-1), respectively, and suitable precision (< 20%). Application of this method for analysis of the musks in real water matrices such as tap, river, sea, and urban wastewater samples resulted in convenient selectivity, high sensitivity and accuracy using the standard addition methodology. The proposed method (SBSE-LD/LVI-GC-MS(SIM)) was shown to be feasible and sensitive, with a low-sample volume requirement, for determination of musk compounds in environmental water matrices at the ultra-trace level, overcoming several disadvantages presented by other sample-preparation techniques.

Quantification of thyrotropin-releasing hormone by liquid chromatography–electrospray mass spectrometry

Thyrotropin-releasing hormone (TRH) is involved in a wide range of biological responses. It has a central role in the endocrine system and regulates several neurobiological activities. In the present study, a rapid, sensitive and selective liquid chromatography-mass spectrometry method for the identification and quantification of TRH has been developed. The methodology takes advantage of the specificity of the selected-ion monitoring acquisition mode with a limit of detection of 1 fmol. Furthermore, the MS/MS fragmentation pattern of TRH has been investigated to develop a selected reaction monitoring (SRM) method that allows the detection of a specific b2 product ion at m/z 249.1, corresponding to the N-terminus dipeptide pyroglutamic acid-histidine. The method has been tested on rat hypothalami to evaluate its suitability for the detection within very complex biological samples.

Liquid chromatography–electrospray ionization mass spectrometry determination of methylphenidate and ritalinic acid in conventional and non-conventional biological matrices

A procedure based on liquid chromatography–electrospray ionization mass spectrometry is described for determination of methylphenidate (MPH) and its principal metabolite ritalinic acid (RA) in plasma, urine, oral fluid and sweat using 3,4-methylendioxypropylamphetamine (MDPA) as internal standard. Aliquots of 100 μL biological fluids and sweat patch were initially treated with acetonitrile, centrifuged, and clear supernatants evaporated and redissolved in 10 mM ammonium acetate. Chromatography was performed on a reversed-phase column using a gradient of 10 mM ammonium acetate and acetonitrile as a mobile phase at a flow rate of 1 mL/min. Separated analytes were confirmed and quantified by positive electrospray ionization mass spectrometry and selected ion monitoring acquisition mode. Limits of quantifications were 1 ng/mL plasma, 1 ng/sweat patch, 0.5 ng/mL oral fluid and urine for MHF; 1 ng/mL plasma and oral fluid, 1 ng/sweat patch, 0.5 ng/mL urine for RA using 100 μL biological fluids or one sweat-patch per assay. Calibration curves were linear over the calibration ranges for both MPH and RA, with r 2 > 0.99. At three concentrations spanning the linear dynamic range of the assay, mean recoveries ranged between 67.9–90.3% for MPH and 36.3–92.4% for RA in the different biological matrices. This method was applied to therapeutic monitoring of MHP and RA in conventional and non-conventional biological matrices from individuals in drug treatment.

Determinação da matéria-prima utilizada na produção do biodiesel adicionado ao diesel mineral através de monitoramento seletivo de íons

The selective ion monitoring acquisition mode in mass spectrometry was applied to identify, in the diesel complex matrix, the raw materials (vegetable oil and alcohol) that originate biodiesel. Biodiesel samples obtained from babassu, castor, palm and soybean vegetable oils and pure fatty acid methyl and ethyl esters were used to develop this method, using specific fragments in mass spectrometry and the window system in gas chromatography. The commercial Brazilian B2 samples were found to be produced with soybean oil, transesterified with methanol.

Development and validation of a liquid chromatography–mass spectrometry assay for hair analysis of methylphenidate

Methylphenidate (MPH) is a phenethylamine derivative used in the treatment of childhood attention-deficit hyperactivity disorder. MPH is biotransformed in the body by the hydrolysis of the methyl ester linkage to its metabolite, ritalinic acid. Whereas both compounds are usually measured in plasma and urine, preliminary observations show that only the parent compound is present in hair from treated individuals. Since in children hair samples can be easily collected without the need for specials skills and exposing a patient to discomfort, hair testing of MPH should be an alternative to check compliance in a wider time-window than if using blood. A procedure based on liquid chromatography–mass spectrometry (LC–MS) has been developed for the determination of MPH in hair of treated children. After addition of 3,4-methylenedioxypropylamphetamine as internal standard, hair samples were overnight digested with 0.1 M HCl at 37 °C. Then, after pH adjustment to 6 using 1N NaOH, and 0.1 M phosphate buffer, the analyte was extracted with Bond–Elut Certify columns. Chromatographic separation was achieved at ambient temperature using a reverse phase column and a mobile phase of 80% 10 mM ammonium acetate–20% acetonitrile with a 20 min gradient program. The mass spectrometer was operated in positive electrospray ionization and selected ion monitoring acquisition mode. The method was validated in the range 0.15–50 ng MPH/mg hair, using 20 mg hair per assay. At three concentrations spanning the linear dynamic range of the assay, mean recoveries ranged between 73.2 and 77.1%. First results show MPH hair concentration varying from 0.15 to 4.17 ng/mg hair, with decreasing drug concentration in distal hair segments, even in children treated with the same MPH dose during the period corresponding to different segments. This fact could be either attributed to sebum or sweat shunt with the most proximal hair segment or drug degradation by cosmetic treatments in more distal segments.

Validation of a Procedure for the Gas Chromatography-Mass Spectrometry Analysis of Cocaine and Metabolites in Pericardial Fluid

A method is described for the simultaneous quantification of cocaine, benzoylecgonine, and cocaethylene in pericardial fluid. Pericardial fluid samples from autopsy casework involving cocaine-related deaths and deaths unrelated to drug abuse were collected. The extraction of cocaine and its metabolites was performed using Bond-Elut Certify columns. Pericardial fluid samples were adjusted to pH 7 and applied to the pre-conditioned cartridges. After the washing steps, compounds were eluted with a mixture of chloroform/isopropanol (80:20) with 2% ammonium hydroxide. The dry extracts were derivatized with pentafluoropropionic anhydride and hexafluoroisopropanol and analyzed by gas chromatography-mass spectrometry using electron impact ionization and selective ion monitoring acquisition. Deuterated internal standards were used. The analytical method developed was linear, sensitive, selective, accurate, and sufficiently precise to be applied routinely in forensic toxicology. In this study, the procedure has been successfully applied to a number of forensic cases involving cocaine intoxication.

Development of a stir-bar-sorptive extraction–liquid desorption–large-volume injection capillary gas chromatographic–mass spectrometric method for pyrethroid pesticides in water samples

Stir-bar-sorptive extraction followed by liquid desorption and large-volume injection capillary gas chromatography with mass spectrometric detection (SBSE-LD-LVI-GC-MS), had been applied for the determination of ultra-traces of eight pyrethroid pesticides (acrinathrin, cypermethrin, deltamethrin, esfenvalerate, fenpropathrin, fenvalerate, and permethrin cis and trans isomers) in water samples. Instrumental calibration for selected-ion monitoring acquisition and conditions that could affect the SBSE-LD efficiency are fully discussed. By performing systematic assays on 30-mL water samples spiked at the 0.10 microg L(-1) level it was established that stir-bars coated with 47 microL polydimethylsiloxane, an equilibrium time of 60 min (750 rpm), 5% methanol as organic modifier, and acetonitrile as back-extraction solvent, provided the best analytical performance to monitor pyrethroid pesticides in water matrices. Good accuracy (81.8-105.0%) and remarkable reproducibility (<11.7%) were obtained, and the experimental recovery data were in good agreement with the theoretical equilibrium described by octanol-water partition coefficients (log K(O/W)), with the exception of acrinathrin for which lower yields were measured. Excellent linear dynamic ranges between 25 and 400 ng L(-1) (r2>0.994), low quantification (3.0-7.5 ng L(-1)) and detection (1.0-2.5 ng L(-1)) limits were also achieved for the eight pyrethroid pesticides studied. The method was successfully used for analysis of tap-water and groundwater matrices spiked at the 0.10 microg L(-1), revealing the suitability of the method for determination of pyrethroid pesticides in real samples. The method was shown be reliable and sensitive and a small volume of sample was required to monitor pyrethroids at ultra-trace levels, in compliance with international regulatory directives on water quality.

Development of a Method for the Detection and Confirmation of the alpha-2 Agonist Amitraz and Its Major Metabolite in Horse Urine

Amitraz (N'-(2,4-dimethylphenyl)-N-[[(2,4-dimethylphenyl)imino]methyl]-N-methyl-methanimidamide) is an alpha-2 adrenergic agonist used in veterinary medicine primarily as a scabicide- or acaricide-type insecticide. As an alpha-2 adrenergic agonist, it also has sedative/tranquilizing properties and is, therefore, listed as an Association of Racing Commissioners International Class 3 Foreign Substance, indicating its potential to influence the outcome of horse races. We identified the principal equine metabolite of amitraz as N-2,4-dimethylphenyl-N'-methylformamidine by electrospray ionization(+)-mass spectrometry and developed a gas chromatographic-mass spectrometric (GC-MS) method for its detection, quantitation, and confirmation in performance horse regulation. The GC-MS method involves derivatization with t-butyldimethylsilyl groups; selected ion monitoring (SIM) of m/z 205 (quantifier ion), 278, 261, and 219 (qualifier ions); and elaboration of a calibration curve based on ion area ratios involving simultaneous SIM acquisition of an internal standard m/z 208 quantifier ion based on an in-house synthesized d(6) deuterated metabolite. The limit of detection of the method is approximately 5 ng/mL in urine and is sufficiently sensitive to detect the peak urinary metabolite at 1 h post dose, following administration of amitraz at a 75-mg/horse intravenous dose.

Quantitative determination of 1-hydroxypyrene in bovine urine samples using high-performance liquid chromatography with fluorescence and mass spectrometric detection

An analytical method was developed to determine quantitatively 1-hydroxypyrene (OHP) in bovine urine samples. The procedure includes an enzymatic hydrolysis to cleave the conjugated metabolite, an enrichment step using solid phase extraction with a non-polar rinse step and elution with dichloromethane. A final clean-up on silicagel was performed before high-performance liquid chromatography (HPLC) analysis and fluorescence detection. Alternatively, HPLC and electrospray ionization in the negative ion mode applying selective ion monitoring acquisition revealed to be a highly sensitive detection method allowing the quantitation of low pg of OHP in the urine samples. The method was successfully applied to the determination of OHP in bovine urine samples from animals living in urban and rural areas. Urine concentrations of OHP were significantly higher (median 8.6 μg l −1) of bovines living close to a highway.