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The proliferation of harmful cyanobacterial algal blooms is of concern due to the associated release of toxins affecting ecosystems and human health. The paralytic shellfish poison saxitoxin (STX) is a small polar alkaloid that can occur in inland and marine aquatic environments. Here, we optimized a fast and sensitive analytical method for the determination of STX, neosaxitoxin (NeoSTX), and their decarbamoyl analogues in surface waters. The method involves a simple filtration, addition of isotope-labelled internal standard (ILIS), and analysis by on-line solid-phase extraction coupled to hydrophilic interaction liquid chromatography high-resolution mass spectrometry (on-line SPE-HILIC-HRMS). Except glass fiber filters, other tested materials (e.g., nylon, nitrocellulose) provided suitable filtration performance. Time-dependent adsorptive losses occurred during the LC-MS batch sequence if glass autosampler vials were used, while no such effect was observed for polypropylene autosampler vials. Matrix effects were evaluated for 4 different quantification scenarios, including external vs. internal curves and neat reagent water vs. matrix-matched curves. Matrix-matched calibration with ILIS correction (NeoSTX- 15 N 7 ) provided the best performance overall. The analytical method was validated in freshwater lake water and estuarine brackish water (30‰ salinity), with suitable determination coefficients (R 2  > 0.9975), matrix spike accuracy (90-107%), and intraday/interday precision (RSD of 0.61-16%). Method limits of detection (LOD in lake water: 0.72-3.9 ng/L) are also improved over most of the recent literature. The method was applied to a set of 302 surface water samples collected in Canada, France, and the United Kingdom, and positive detections were reported for STX (max: 98 ng/L), decarbamoyl-STX (max: 15 ng/L), and NeoSTX (max: 87 ng/L)., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The list of endocrine disrupting compounds (EDCs) defined under U.S. EPA Method 539 was recently expanded to include additional hormones and bisphenol A (BPA). Here, we validated a fast and robust alternative method compliant with Method 539.1 requirements in diverse water matrixes (i.e., ultra-pure water, tap water, surface water, and wastewater influent and effluent). Automated large volume injection solid phase extraction (SPE) coupled on-line to ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) was investigated for this purpose. The surveyed molecules included 13 EPA-priority hormones (testosterone, progesterone, medroxyprogesterone, levonorgestrel, norethindrone, androstenedione, estrone, β-estradiol, α-estradiol, equilin, equilenin, ethinylestradiol, estriol) and BPA. Combinations of ionization source and mobile phases were optimized for improved sensitivity. Suitable chromatographic performances were obtained and the implementation of an on-line SPE washing step consecutive to sample loading was investigated. On-line SPE extraction efficiencies in acceptable ranges (64-79%) and detection limits in the order of nanogram per liter or sub-nanogram per liter were obtained. The linearity range extended over 2-3 orders of magnitude, with determination coefficients (R 2 ) typically > 0.9980. Robust precision and trueness complying with acceptance criteria (70-130%) were obtained for the scope of analytes/matrix combinations. Limited internal standard variations were also observed across samples (±18%), well within the ±50% acceptance criterion. The method was successfully applied to field-collected samples in Canada and summed EDC concentrations were reported in the range of 0.80-2.8 ng L -1 , 6.8-19 ng L -1 , 260-790 ng L -1 , and 37-360 ng L -1 in tap water, surface water, effluent and influent wastewater samples, respectively., (Copyright © 2019 Elsevier B.V. All rights reserved.)

A fast and high-throughput method is proposed for the determination of total microcystins (ΣMC) in environmental surface waters. After a 1-h Lemieux-von Rudloff oxidation step to yield the 2-methyl-3-methoxy-4-phenylbutyric acid (MMPB) moiety, samples were quenched, filtered, and directly analyzed. This was achieved via solid phase extraction (SPE) coupled on-line to ultra-high performance liquid chromatography electrospray ionization triple stage quadrupole mass spectrometry. The choice of on-line SPE settings was conducted using experimental designs. Given the matrix complexity of oxidation extracts, the on-line desalting step was found to be a critical parameter to ensure suitable method robustness. The on-line sample loading volume was 5mL, and the wash volume applied for on-line desalting was 3mL. Instrumental analysis was performed in just 8min. The method limit of quantification was 0.5ngL -1 ΣMC (i.e. 2000 times lower than the current World Health Organization - WHO drinking water guideline). Excellent determination coefficients were observed for matrix-free and matrix-based calibration curves alike, and the linearity range tested spanned∼4 orders of magnitude. Accuracy and intermediate precision did not depend on the spike level and proved satisfactory (in the range of 93-110% and 3-6%, respectively). A thorough assessment of instrumental matrix effects was conducted by comparing standard additions curves in several lake and river oxidation extracts with the matrix-free reference. Regardless of the internal standard used (4-PB or D3-MMPB), instrumental matrix effects were efficiently compensated. The matrix effect that may occur at the earlier sample preparation stage was evaluated separately. While the oxidation step was generally not complete (yield ∼65%), the conversion rates of MCs into MMPB remained within a consistent range of values regardless of matrix type. No significant back-pressure was observed upon consecutive injections of oxidation-based samples, while the instrumental sensitivity remained unaffected. The herein described method could therefore be eligible for future large-scale monitoring surveys. The method was applied to a selection of surface water samples (n=30) collected across the province of Québec, Canada, and the results were compared to those achieved by an individual variant analysis of 8 MC congeners and a commercial ELISA kit., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Trace emerging contaminants (ECs) occur in both waste and surface waters that are rich in particulates that have been found to sorb several organic contaminants. An analytical method based on off-line solid-phase extraction (SPE) followed by liquid chromatography-mass spectrometry (LC-MS) analysis was developed for the detection and quantification of 31 ECs from surface water, wastewater, suspended particulate matter (SPM) as well as sediments. Lyophilized sediments and air-dried SPM were subjected to ultrasonic extraction. Water samples and extracts were then concentrated and cleaned-up by off-line SPE. Quantification was realized using a Q Exactive mass spectrometer in both full scan (FS) and MS 2 modes. These two modes were optimized and compared to determine which one was the most suitable for each matrix studied. Yeast estrogen screen assay (YES-assay) adapted from the direct measurement of estrogenic activity without sample extraction was tested on filtered wastewater samples. An endocrine disrupting effect was detected in all effluent samples analyzed with estradiol equivalent concentrations ranging from 4.4 to 720 ng eq E2 L -1 for the WWTP-1 and 6.5-42 ng eq E2 L -1 for the WWTP-2. The analytical methods were also applied on six samples of surface water, the corresponding SPM, the sediments and thirty-nine effluent samples from two wastewater treatment plants (WWTPs) sampled over a period of five months (February to June 2014)., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

An alternative analysis technique for the quantitation of 15 poly- and perfluoroalkyl substances (PFASs) in water matrices is reported. Analysis time between each sample was reduced to less than 20s, all target molecules being analyzed in a single run with the use of laser diode thermal desorption atmospheric pressure chemical ionization (LDTD/APCI) coupled with high resolution accurate mass (HRMS) orbitrap mass spectrometry. LDTD optimal settings were investigated using either one-factor-at-a-time or experimental design methodologies, while orbitrap parameters were optimized simultaneously by means of a Box-Behnken design. Following selection of an adequate sample concentration and purification procedure based on solid-phase extraction and graphite clean-up, the method was validated in an influent wastewater matrix. Environmentally significant limits of detection were reported (0.3-4ngL(-1) in wastewater and 0.03-0.2ngL(-1) in surface water) and out of the 15 target analytes, 11 showed excellent accuracies (±20% of the target values) and recovery rates (75-125%). The method was successfully applied to a selection of environmental samples, including wastewater samples in 7 locations across Canada, as well as surface and tap water samples from the Montreal region, providing insights into the degree of PFAS contamination in this area., (Copyright © 2015 Elsevier B.V. All rights reserved.)

A new coating material was used for a stir bar sorptive extraction (SBSE) method coupled to a high throughput sample analysis technique. This allowed for a simple procedure for fast determinations of eight steroid hormones (estriol, estradiol, ethynylestradiol, estrone, progesterone, medroxyprogesterone, levonorgestrel, northindrone) in water. Sample pre-treatment was performed using an in-house SBSE method based on a polydimethylsiloxane/phenyltrimethylsiloxane/β-cyclodextrin sol-gel material. The analytes were desorbed by liquid extraction prior to their analysis by laser diode thermal desorption/atmospheric pressure chemical ionization coupled to tandem mass spectrometry (LDTD-APCI-MS/MS). Several parameters, including ionic strength, volume and time of extraction as well as volume and time of desorption, were investigated to maximize extraction efficiency by SBSE in aqueous solutions. The in-house stir bar showed good reproducibility and could be used for at least 50 extractions without affecting analytical performance. The recoveries of the spiked steroid hormones ranged from 55% to 96% in all water matrices studied (HPLC grade water, tap water and raw wastewater). Only one compound showed poor recovery values (<2% for estriol) in all matrices. The method detection limits (MDLs) in real matrices were within the range of 0.1-0.3 μg L(-1) except for estriol at 48 μg L(-1). The extraction performance of the in-house SBSE for the eight selected hormones was also compared with that of a commercially-available stir bar coated with polydimethylsiloxane (PDMS). This novel stir bar coating could prove to be useful method for the detection and quantification of trace levels of steroid hormones., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Plasmodium falciparum is the causative agent of malaria, a deadly infectious disease for which treatments are scarce and drug-resistant parasites are now increasingly found. A comprehensive method of identifying and quantifying metabolites of this intracellular parasite could expand the arsenal of tools to understand its biology, and be used to develop new treatments against the disease. Here, we present two methods based on liquid chromatography tandem mass spectrometry for reliable measurement of water-soluble metabolites involved in phospholipid biosynthesis, as well as several other metabolites that reflect the metabolic status of the parasite including amino acids, carboxylic acids, energy-related carbohydrates, and nucleotides. A total of 35 compounds was quantified. In the first method, polar compounds were retained by hydrophilic interaction chromatography (amino column) and detected in negative mode using succinic acid-(13)C(4) and fluorovaline as internal standards. In the second method, separations were carried out using reverse phase (C18) ion-pair liquid chromatography, with heptafluorobutyric acid as a volatile ion pairing reagent in positive detection mode, using d(9)-choline and 4-aminobutanol as internal standards. Standard curves were performed in P. falciparum-infected and uninfected red blood cells using standard addition method (r(2)>0.99). The intra- and inter-day accuracy and precision as well as the extraction recovery of each compound were determined. The lower limit of quantitation varied from 50pmol to 100fmol/3×10(7)cells. These methods were validated and successfully applied to determine intracellular concentrations of metabolites from uninfected host RBCs and isolated Plasmodium parasites., (Copyright © 2012 Elsevier B.V. All rights reserved.)