Rapid and sensitive gas chromatography–ion-trap tandem mass spectrometry method for the determination of tobacco-specific N-nitrosamines in secondhand smoke

Tobacco-specific nitrosamines (TSNAs) are some of the most potent carcinogens in tobacco and cigarette smoke. Accurate quantification of these chemicals is needed to help assess public health risks. We developed and validated a specific and sensitive method to measure four TSNAs adsorbed to model surfaces and secondhand smoke (SHS) particles using gas chromatography–ion-trap tandem mass spectrometry. In an 18-m³ room-sized chamber, a smoking machine generated realistic concentrations of SHS that were actively sampled on Teflon-coated fiber glass (TCFG) filters, and passively sampled on cellulose substrates. A simple solid–liquid extraction protocol using methanol as solvent was successfully applied to both substrates with recoveries ranging from 85 to 115%. For each TSNA, tandem MS parameters were optimized and the major fragmentation pathways were elucidated. The method showed excellent performance, with a linear dynamic range from 2 to 1000 ng mL⁻¹, low detection limits (S/N > 3) of 30–300 pg mL⁻¹ and precision with experimental errors below 10% for all compounds. Moreover, no interfering peaks were observed, indicating a high selectivity of MS/MS without the need for a sample clean-up step. This method provides a suitable analytical tool to detect and quantify traces of TSNA in indoor environments polluted with SHS.     

Monitoring of the smoking process by multicommutation Fourier transform infrared spectroscopy

Nicotine was selected as the target molecule for monitoring of the smoking process by multicommutation Fourier Transform Infrared spectroscopy (FTIR). The method involved the use of CHCl₃ for on-line extraction of nicotine from tobacco, cigarette filters and tobacco ash from NH₄OH alkalinized samples, and absorbance measurement of the characteristic band at 1316 cm⁻¹ in the stopped-flow mode, by obtaining the peak area in the range between 1334 and 1300 cm⁻¹. Under the best operational conditions, the procedure developed provided a detection limit of 0.05 mg mL⁻¹ nicotine, corresponding to 0.5 mg g⁻¹ in the solid sample, a relative standard deviation less than 2.5%, and a sampling frequency of 12 determinations h⁻¹. It can be concluded that nicotine migrates in the smoke mainstream towards the filter during the smoking process. The smoking of cigarettes and cigars is different. Nicotine is retained weakly by both tobacco and filter in the case of cigarettes, and strongly by the unburned tobacco in cigars. The incomplete smoking of cigars and cigarettes reduces nicotine intake and thus reduces the additive effect.     

High-performance liquid chromatography with fluorescence detection and ultra-performance liquid chromatography with electrospray tandem mass spectrometry method for the determination of indoleamine neurotransmitters and their metabolites in sea lamprey plasma

We present a comparison of two sensitive methods, HPLC with fluorescence detector (HPLC/FLD) and UPLC with electrospray tandem mass spectrometry (UPLC/MS/MS), for the determination of indoleamine neurotransmitters (NTs) and their metabolites in sea lamprey plasma samples. Liquid–liquid extraction (LLE) and solid-phase extraction (SPE) were also tested for recovery and matrix effect. The recoveries of SPE determined by HPLC/FLD and UPLC/MS/MS ranged from 75 to 123% and 78 to 105%, respectively, while the recoveries of LLE ranged from 45 to 73% and 48 to 75%, respectively. SPE combined with HPLC/FLD and UPLC/MS/MS to determine the target analytes in plasma samples were validated of the sensitivity, reproducibility, accuracy and precision. Both methods exhibited excellent linearity in the range of 0.2–50 ng mL⁻¹ for all analytes. The limits of detection (LOD) varied from 0.04 ng mL⁻¹ to 0.13 ng mL⁻¹ for HPLC/FLD method and 0.003 ng mL⁻¹ to 0.02 ng mL⁻¹ for UPLC/MS/MS method. The inter-day accuracy ranged from 82.5 to 127.0% for HPLC/FLD and 93.0 to 113.0% for UPLC/MS/MS. The inter-day precision ranged from 9.9 to 32.3% for HPLC/FLD and 5.4 to 13.2% for UPLC/MS/MS. These results demonstrated that the values obtained by both methods were within the satisfactory range and the UPLC/MS/MS method provided more accurate and precise measurements than HPLC/FLD method. The comparison is of great importance to determine the available detectors, considering the complexity and expensiveness versus quality parameters. These two methods were applied to the analysis of four important indoleamine neurotransmitter analytes (5-hydroxytryptamine, 5-hydroxyindole-3-acetic acid, tryptamine and melatonin) in sea lamprey plasma samples.     

Development of vial wall sorptive extraction and its application to determination of progesterone in human serum

A novel sample preparation method, vial wall sorptive extraction (VWSE), which uses a vial whose internal wall is coated with polydimethylsiloxane (PDMS), was developed. The method was applied to the determination of progesterone in human serum sample. Human serum sample (0.5 mL) spiked with progesterone-¹³C₂ was pipetted into the VWSE device and vortex mixing was performed for 30 min. Then, the serum sample was removed and the vial rinsed with purified water. Fifty microliter of methanol as liquid desorption (LD) solvent was pipetted into the VWSE device and vortex mixing was performed for 10 min. Then, the extract was analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The correlation coefficient (r) of the calibration curve over the concentration range of 0.5–200 ng mL⁻¹ was 0.999. The limit of detection (LOD) and the limit of quantification (LOQ) were 0.1 and 0.5 ng mL⁻¹, respectively. The relative recoveries were 97.9% (RSD: 4.4%, n = 6) and 102.8% (RSD: 1.1%, n = 6) for progesterone spiked at 5 and 50 ng mL⁻¹, respectively. This simple, accurate, sensitive, and selective analytical method is applicable to the trace analysis of a minute amount of sample.     

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.     

Determination of ketamine and metabolites in urine by liquid chromatography-mass spectrometry

We have developed an analytical method by using liquid chromatography-mass spectrometry (LC-MS) to determine ketamine and its metabolites in urine. The ionization efficiency between two ionization modes (ESI and APCI) of LC-MS was compared to each other. An easy and simple sample preparation of urine samples was made by passing samples through a 0.22 μm PVDF syringe filter. The results indicated that the ionization efficiency of positive APCI mode is better than positive ESI mode for determination of trace ketamines. A wide linearity range of the research is from 5 to 250 ng mL⁻¹ and the detection limits for ketamine, norketamine and dehydronorketamine were 0.95, 0.48 and 0.33 ng mL⁻¹, respectively. The proposed method was tested by analyzing ketamine and metabolites in the urines of volunteers. The concentrations of ketamine, norketamine and dehydronorketamine are ranged of 5.4-131.0, 12.5-74.1 and 22.8-278.9 ng mL⁻¹, respectively and the ketamines concentration profiles in human urine were also determined. The results demonstrate the suitability of liquid chromatography-mass spectrometry approach to analyze trace amount of ketamine and its metabolites in urine.     

Preparation and evaluation of an immunoaffinity sorbent with Fab′ antibody fragments for the analysis of opioid peptides by on-line immunoaffinity solid-phase extraction capillary electrophoresis–mass spectrometry

An immunoaffinity (IA) sorbent with antibody fragments was prepared for the analysis of opioid peptides by on-line immunoaffinity solid-phase extraction capillary electrophoresis–mass spectrometry (IA-SPE-CE–MS). The antibody fragmentation was evaluated by MALDI-TOF-MS. Fab′ fragments obtained from a polyclonal IgG antibody against Endomorphins 1 and 2 (End1 and End2) were covalently attached to succinimidyl silica particles to prepare the IA sorbent. An IA-SPE-CE–MS methodology was established analyzing standard solutions of End1 and End2 and acceptable repeatability, linearity ranges and LODs (0.5 and 5 ng mL⁻¹, respectively) were obtained. The LOD of End1 was slightly better than that previously obtained using an IA sorbent with intact antibodies (1 ng mL⁻¹). In human plasma samples, End1 and End2 could be detected at 1 and 50 ng mL⁻¹, respectively, which meant an improvement of 100 and 2-fold with regard to the LODs using an IA sorbent with intact antibodies (100 ng mL⁻¹).     

Food safety evaluation: Detection and confirmation of chloramphenicol in milk by high performance liquid chromatography-tandem mass spectrometry

A simple and rapid procedure for extraction of chloramphenicol (CAP) in milk and analysis by high-performance liquid chromatography coupled with quadrupole mass spectrometry in tandem was developed. The method consisted of one step of liquid-liquid extraction using ethyl acetate and acidified water (10 mmol L⁻¹ formic acid) and HPLC-MS/MS detection. CAP-D5 was used as internal standard. The method was validated according to Commission Decision 2002/657/EC. The calibration curves were linear, with typical r² values higher than 0.98. Absolute recovery of CAP from milk proved to be more than 95%, however CAP-D5 absolute recovery was 75%. The method was accurate and reproducible, being successfully applied to the monitoring of CAP in milk samples obtained from the Brazilian market. Decision limit (CCα) was 0.05 ng mL⁻¹ and detection capability (CCβ) was 0.09 ng mL⁻¹.     

Next generation planar waveguide detection of microcystins in freshwater and cyanobacterial extracts,utilising a novel lysis method for portable sample preparation and analysis

The study details the development of a fully validated, rapid and portable sensor based method for the on-site analysis of microcystins in freshwater samples. The process employs a novel lysis method for the mechanical lysis of cyanobacterial cells, with glass beads and a handheld frother in only 10 min. The assay utilises an innovative planar waveguide device that, via an evanescent wave excites fluorescent probes, for amplification of signal in a competitive immunoassay, using an anti-microcystin monoclonal with cross-reactivity against the most common, and toxic variants. Validation of the assay showed the limit of detection (LOD) to be 0.78 ng mL⁻¹ and the CCβ to be 1 ng mL⁻¹. Robustness of the assay was demonstrated by intra- and inter-assay testing. Intra-assay analysis had % C.V.s between 8 and 26% and recoveries between 73 and 101%, with inter-assay analysis demonstrating % C.V.s between 5 and 14% and recoveries between 78 and 91%. Comparison with LC–MS/MS showed a high correlation (R² = 0.9954) between the calculated concentrations of 5 different Microcystis aeruginosa cultures for total microcystin content. Total microcystin content was ascertained by the individual measurement of free and cell-bound microcystins. Free microcystins can be measured to 1 ng mL⁻¹, and with a 10-fold concentration step in the intracellular microcystin protocol (which brings the sample within the range of the calibration curve), intracellular pools may be determined to 0.1 ng mL⁻¹. This allows the determination of microcystins at and below the World Health Organisation (WHO) guideline value of 1 μg L⁻¹. This sensor represents a major advancement in portable analysis capabilities and has the potential for numerous other applications.     

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.     

Determination of 48 pesticides and their main metabolites in water samples by employing sonication and liquid chromatography-tandem mass spectrometry

In this work, a rapid and sensitive analytical multiresidue method has been developed for the simultaneous determination of 48 pesticides and 19 metabolites in waters (tap, leaching and sewage), using liquid chromatography-tandem mass spectrometry (LC-MS/MS) with triple quadrupole in selected reaction monitoring (SRM) mode. The procedure involves initial single phase extraction of samples with acetonitrile by sonication, followed by liquid-liquid partition aided by “salting out” process using NaCl. Matrix influence on recoveries was evaluated for the three waters. More than 50% of the compound presented very low signal suppression. The method presents good linearity over the range assayed 10-500 μg L⁻¹ and the most frequent detection limits was 0.05 ng mL⁻¹. The average recovery by the LC-MS/MS method obtained for these compounds varied from 74.6 to 111.2% with a relative standard deviation between 2.5 and 8.9%. The proposed method was used to determine pesticides levels in leaching water samples from 5 lysimeters from an experimental greenhouse located in Murcia.     

A high-throughput method for determination of metabolites of organophosphate flame retardants in urine by ultra performance liquid chromatography–high resolution mass spectrometry

Organophosphate triesters are common flame retardants used in a wide variety of consumer products from which they can migrate and pollute the indoor environment. Humans may thus be continuously exposed to several organophosphate triesters which might be a risk for human health. An analytical method based on direct injection of 5 μL urine into an ultra performance liquid chromatography system coupled to a time-of-flight mass spectrometry has been developed and validated to monitor exposure to organophosphate triesters through their respective dialkyl and diaryl phosphate metabolites (DAPs). The targeted analytes were: di-n-butyl phosphate (DNBP), diphenyl phosphate (DPHP), bis(2-butoxyethyl) phosphate (BBOEP), bis(2-chloroethyl) phosphate (BCEP), bis(1-chloro-2-propyl) phosphate (BCPP) and bis(1,3-dichloro-2-propyl) phosphate (BDCIPP). Separation was achieved in less than 3 min on a short column with narrow diameter and small particle size (50 mm × 2.1 mm × 1.7 μm). Different mobile phases were explored to obtain optimal sensitivity. Acetonitrile/water buffered with 5 mM of ammonium hydroxide/ammonium formate (pH 9.2) was the preferred mobile phase. Quantification of DAPs was performed using deuterated analogues as internal standards in synthetic urine (averaged DAP accuracy was 101%; RSD 3%). Low method limits of quantification (MLQ) were obtained for DNBP (0.40 ng mL⁻¹), DPHP (0.10 ng mL⁻¹), BDCIPP (0.40 ng mL⁻¹) and BBOEP (0.60 ng mL⁻¹), but not for the most polar DAPs, BCEP (∼12 ng mL⁻¹) and BCPP (∼25 ng mL⁻¹). The feasibility of the method was tested on 84 morning urine samples from 42 mother and child pairs. Only DPHP was found above the MLQ in the urine samples with geometric mean (GM) concentrations of 1.1 ng mL⁻¹ and 0.57 ng mL⁻¹ for mothers and children respectively. BDCIPP was however, detected above the method limit of detection (MLD) with GM of 0.13 ng mL⁻¹ and 0.20 ng mL⁻¹. While occasionally detected, the GM of DNBP and BBOEP were below MLD in both groups.     

Development, validation and application of a method based on DI-SPME and GC-MS for determination of pesticides of different chemical groups in surface and groundwater samples

A simple and rapid method based on solid-phase micro extraction (SPME) technique followed by gas chromatography-mass spectrometry with selected ion monitoring (GC-MS, SIM) was developed by the simultaneous determination of 16 pesticides of seven different chemical groups [Six organophosphorus (trichlorfon, diazinon, methyl parathion, malathion, fenthion and ethyon), three pyrethroids (bifenhin, permethrin, cypermethrin), two imidazoles (imazalil and prochloraz), two strobilurins (azoxystrobin and pyraclostrobin), one carbamate (carbofuran), one tetrazine (clofentezine), and one triazole (difenoconazole)] in water. The pesticides extraction was done with direct immersion mode (DI-SPME) of the polyacrilate fiber (PA 85 µm). The extraction temperature was adjusted to 50 °C during 30 min, while stirring at 250 rpm was applied. After extraction, the fiber was introduced in the GC injector for thermal desorption for 5 min. at 280 °C. The method was validated using ultra pure water samples fortified with pesticides at different concentration levels and shows good linearity in the concentrations between 0.05 and 250.00 ng mL^− 1. The LOD and LOQ ranged, from 0.02 to 0.30 ng mL^− 1 and 0.05 to 1.00 ng mL^− 1, respectively. Intra-day and inter-day precisions were determined in two concentration levels (5.00 and 50.00 ng mL^− 1). Intra-day relative standard deviation (%R.S.D.) ranged between 3.6 and 13.6%, and inter-day (%R.S.D.) ranged between 6.3 and 18.5%. Relative recovery tests were carried out spiking the ultra pure sample with standards in three different concentration levels 0.20, 5.00 and 50.00 ng mL^− 1. The recovery at 0.20 ng mL^− 1 level varied from 86.4 ± 9.4% to 108.5 ± 10.5%, at 5.00 ng mL^− 1 level varied from 77.5 ± 10.8% to 104.6 ± 9.6% and at 50.00 ng mL^− 1 level varied from 70.2 ± 4.6% to 98.4 ± 8.5%. The proposed SPME method was applied in twenty-six water samples collected in the “Platô de Neópolis”, State of Sergipe, Brazil. Methyl parathion was detected in five samples with an average concentration of 0.17 ng mL^− 1 and bifenthrin, pyraclostrobin and azoxystrobin residues were found in three samples with average concentrations of 2.28, 3.12 and 0.15 ng mL^− 1, respectively.     

Leachability and analytical speciation of antimony in coal fly ash

A new procedure was described with multiwalled carbon nanotubes as solid phase extraction packing material for the trace analysis of nicosulfuron, thifensulfuron and metsulfuron-methyl in water samples. The possible parameters influencing the enrichment were optimized and the optimal conditions were as followed: eluent, sample pH, flow rate and sample volume were acetonitrile containing 1% acetic acid, pH 3, 8 mL min⁻¹ and 500 mL, respectively. Under the optimal chromatographic separation and SPE conditions, the linear range, detection limit (S/N = 3) and precision (R.S.D., n = 6) were 0.04-40 ng mL⁻¹, 6.8 ng L⁻¹ and 2.5% for nicosulfuron, 0.04-40 ng mL⁻¹, 11.2 ng L⁻¹ and 5.4% for thifensulfuron, 0.02-20 ng mL⁻¹, 5.9 ng L⁻¹, 2.1% for metsulfuron-methyl, respectively. The established method was well employed to determine nicosulfuron, thifensulfuron and metsulfuron-methyl in tap water, seawater, reservoir water and well water samples, and satisfactory results were obtained, the spiked recoveries in the range of 87.2-100.7%, 96.5-105.6% and 83.7-111.1% for them each, respectively.     

Production and characterization of a broad-specificity polyclonal antibody for O,O-diethyl organophosphorus pesticides and a quantitative structure-activity relationship study of antibody recognition

Polyclonal antibody (PAb) with broad-specificity for O,O-diethyl organophosphorus pesticides (OPs) against a generic hapten, 4-(diethoxyphosphorothioyloxy)benzoic acid, was produced. The obtained PAb showed high sensitivity to seven commonly used O,O-diethyl OPs in a competitive indirect enzyme-linked immunosorbent assay (ciELISA) using a heterologous coating antigen, 4-(3-(diethoxyphosphorothioyloxy)phenylamino)-4-oxobutanoic acid. The 50% inhibition value (IC₅₀) was 348 ng mL⁻¹ for parathion, 13 ng mL⁻¹ for coumaphos, 22 ng mL⁻¹ for quinalphos, 35 ng mL⁻¹ for triazophos, 751 ng mL⁻¹ for phorate, 850 ng mL⁻¹ for dichlofenthion, and 1301 ng mL⁻¹ for phoxim. The limit of detection (LOD) met the ideal detection criteria of all the seven OP residues. A quantitative structure-activity relationship (QSAR) model was constructed to study the mechanism of antibody recognition using multiple linear regression analysis. The results indicated that the frontier-orbital energies (energy of the highest occupied molecular orbital, E_HOMO, and energy of the lowest unoccupied molecular orbital, E_LUMO) and hydrophobicity (log of the octanol/water partition coefficient, log P) were mainly responsible for the antibody recognition. The linear equation was log(IC₅₀) = −63.274E_HOMO + 15.985E_LUMO + 0.556 log P − 25.015, with a determination coefficient (r²) of 0.908.     

Development and validation of a high-throughput double solid phase extraction-liquid chromatography-tandem mass spectrometry method for the determination of tetrodotoxin in human urine and plasma

A sensitive analytical method for the determination of tetrodotoxin (TTX) in urine and plasma matrices was developed using double solid phase extraction (C18 and hydrophilic interaction liquid chromatography) and subsequent analysis by HPLC coupled with tandem mass spectrometry. The double SPE sample cleanup efficiently reduced matrix and ion suppression effects. Together with the use of ion pair reagent in the mobile phase, isocratic elution became possible which enabled a shorter analysis time of 5.5 min per sample. The assay results were linear up to 500 ng mL⁻¹ for urine and 20 ng mL⁻¹ for plasma. The limit of detection and limit of quantification were 0.13 ng mL⁻¹ and 2.5 ng mL⁻¹, respectively, for both biological matrices. Recoveries were in the range of 75-81%. To eliminate the effect of dehydration and variations in urinary output, urinary creatinine-adjustment was made. TTX was quantified in eight urine samples and seven plasma samples from eight patients suspected of having TTX poisoning. TTX was detected in all urine samples, with concentrations ranging from 17.6 to 460.5 ng mL⁻¹, but was not detected in any of the plasma samples. The creatinine-adjusted TTX concentration in urine (ranging from 7.4 to 41.1 ng μmol⁻¹ creatinine) correlated well with the degree of poisoning as observed from clinical symptoms.     

Silica gel-polyethylene glycol as a new adsorbent for solid phase extraction of cobalt and nickel and determination by flame atomic absorption spectrometry

In this paper a novel solid phase extraction method to determine Co(II) and Ni(II) using silica gel-polyethylene glycol (Silica-PEG) as a new adsorbent is described. The method is based on the adsorption of cobalt and nickel ions in alkaline media on polyethylene glycol-silica gel in a mini-column, elution with nitric acid and determination by flame atomic absorption spectrometry. The adsorption conditions such as NaOH concentration, sample volume and amount of adsorbent were optimized in order to achieve highest sensitivity. The calibration graph was linear in the range of 0.5-200.0 ng mL⁻¹ for Co(II) and 2.0-100.0 ng mL⁻¹ for Ni(II) in the initial solution. The limit of detection based on 3S_b was 0.37 ng mL⁻¹ for Co(II) and 0.71 ng mL⁻¹ for Ni(II). The relative standard deviations (R.S.D.) for ten replicate measurements of 40 ng mL⁻¹ of Co(II), and Ni(II) were 3.24 and 3.13%, respectively. The method was applied to determine Co(II) and Ni(II) in black tea, rice flour, sesame seeds, tap water and river water samples.     

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).     

Highly sensitive capillary electrophoresis-mass spectrometry for rapid screening and accurate quantitation of drugs of abuse in urine

The combination of capillary electrophoresis (CE) and mass spectrometry (MS) is particularly well adapted to bioanalysis due to its high separation efficiency, selectivity, and sensitivity; its short analytical time; and its low solvent and sample consumption. For clinical and forensic toxicology, a two-step analysis is usually performed: first, a screening step for compound identification, and second, confirmation and/or accurate quantitation in cases of presumed positive results. In this study, a fast and sensitive CE-MS workflow was developed for the screening and quantitation of drugs of abuse in urine samples. A CE with a time-of-flight MS (CE-TOF/MS) screening method was developed using a simple urine dilution and on-line sample preconcentration with pH-mediated stacking. The sample stacking allowed for a high loading capacity (20.5% of the capillary length), leading to limits of detection as low as 2 ng mL⁻¹ for drugs of abuse. Compound quantitation of positive samples was performed by CE-MS/MS with a triple quadrupole MS equipped with an adapted triple-tube sprayer and an electrospray ionization (ESI) source. The CE-ESI-MS/MS method was validated for two model compounds, cocaine (COC) and methadone (MTD), according to the Guidance of the Food and Drug Administration. The quantitative performance was evaluated for selectivity, response function, the lower limit of quantitation, trueness, precision, and accuracy. COC and MTD detection in urine samples was determined to be accurate over the range of 10–1000 ng mL⁻¹ and 21–1000 ng mL⁻¹, respectively.     

Online In-Tube Solid-Phase Microextraction Coupled to Liquid Chromatography–Tandem Mass Spectrometry for the Determination of Tobacco-Specific Nitrosamines in Hair Samples

Active and passive smoking are serious public health concerns Assessment of tobacco smoke exposure using effective biomarkers is needed. In this study, we developed a simultaneous determination method of five tobacco-specific nitrosamines (TSNAs) in hair by online in-tube solid-phase microextraction (SPME) coupled to liquid chromatography-tandem mass spectrometry (LC–MS/MS). TSNAs were extracted and concentrated on Supel-Q PLOT capillary by in-tube SPME and separated and detected within 5 min by LC–MS/MS using Capcell Pak C18 MGIII column and positive ion mode multiple reaction monitoring systems. These operations were fully automated by an online program. The calibration curves of TSNAs showed good linearity in the range of 0.5–1000 pg mL^–1 using their stable isotope-labeled internal standards. Moreover, the limits of detection (S/N = 3) of TSNAs were in the range of 0.02–1.14 pg mL^–1, and intra-day and inter-day precisions were below 7.3% and 9.2% (n = 5), respectively. The developed method is highly sensitive and specific and can easily measure TSNA levels using 5 mg hair samples. This method was used to assess long-term exposure levels to tobacco smoke in smokers and non-smokers.