In-port derivatization coupled to different extraction techniques for the determination of alkylphenols in environmental water samples.

Large volume injection (LVI)-in port silylation coupled to gas chromatography-mass spectrometry (GC-MS) for the determination of alkylphenols (APs) in water samples applying four different extraction approaches was evaluated. Among the variables studied for in-port derivatization, vent time, cryo-focusing temperature and the ratio solvent volume/N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) volume were optimized using an experimental design approach. Regarding the extraction techniques, different approaches previously optimized in the research group were tested. On the one hand different polymeric materials were tested: silicon rod (SR), polyethersulfone (PES) and polydimethylsiloxane (PDMS), the latter in the stir-bar sorptive extraction format (SBSE-PDMS). PES was chosen among the polymeric materials due to the higher recoveries (compared with SR) and lower price (compared to PDMS in the stir-bar sorptive extraction, SBSE-PDMS). Both MASE and PES protocols were selected at this point for further method validation and application to real samples. Finally, the developed methods were validated and applied to the determination of target analytes in various aqueous environmental matrices, including estuarine water and wastewater. Acceptable repeatability in the case of MASE (5-17%) and PES (7-21%) procedures and method detection limits (MDLs, 5-123 and 28-328 ng L(-1) for PES and MASE, respectively) were obtained for most analytes. In terms of apparent recoveries in the presence of matrix, estuarine and effluent samples showed no significant matrix effect (apparent recoveries in the 73-121% for PES and 74-128% for MASE), while a stronger matrix effect was observed for influent wastewater samples (98-132% for PES and 65-156% for MASE). Both MASE and PES extractions combined with LVI-in-port derivatization-GC-MS were applied to the determination of APs in the estuary of Bilbao (Gulf of Biscay, Spain).

Comparison between GC-MS and GC-ICPMS using isotope dilution for the simultaneous monitoring of inorganic and methyl mercury, butyl and phenyl tin compounds in biological tissues.

The aim of this work is to compare simultaneous isotope dilution analysis of organotin and organomercury compounds by gas chromatography-mass spectrometry (GC-MS) and gas chromatography-inductively coupled plasma mass spectrometry (GC-ICP/MS) on certified bivalve samples. These samples were extracted by microwave with tetramethylammonium hydroxide (TMAH). Derivatization with both NaBEt4 and NaBPr4 was evaluated, and analytical performances were compared. Two CRM materials, BCR-710 and CRM-477, were analyzed by both techniques to verify accuracy. A mixed spike containing (201)Hg-enriched methylmercury (MeHg), (199)Hg-enriched inorganic mercury (iHg), (119)Sn-enriched monobutyltin (MBT), dibutyltin (DBT), and tributyltin (TBT) as well as homemade (116)Sn-enriched monophenyltin (MPT), diphenyltin (DPT), and triphenyltin (TPT) was used for the isotope dilution analysis of samples. The two techniques studied were compared in terms of classic analytical parameters: linearity, precision or repeatability (i.e., percent relative standard deviation, RSD%), limit of detection (LOD), and limit of quantification (LOQ), showing excellent linearity, precision below 12% for all analytes, and LOQs of 0.06-1.45 pg for GC-MS and 0.02-0.27 pg for GC-ICP/MS.

Selenium metabolomics in yeast using complementary reversed-phase/hydrophilic ion interaction (HILIC) liquid chromatography-electrospray hybrid quadrupole trap/Orbitrap mass spectrometry.

A high efficiency chromatographic separation on a porous graphitic carbon stationary phase was developed for a large-scale separation of selenium metabolites in Se-rich yeast prior to their identification by electrospray hybrid quadrupole trap/Orbitrap mass spectrometry (Orbitrap MS(n)). The reversed-phase (RP) separation mode offered distinctly higher separation efficiency than the hydrophilic ion interaction (HILIC) mode. The latter was nevertheless complementary and useful to validate the detection of several compounds. The method allowed the detection of 64 metabolites including 30 SeSe or SeS conjugates (3 triple S/Se/S ones) and 14 selenoethers. 21 previously unreported metabolites were detected on the basis of the selenium isotopic pattern usually matched with the sub-ppm mass accuracy. 9 of these metabolites were subsequently identified using the multi-stage high mass accuracy (<5ppm) mass spectrometry. The identified metabolites (and their groups) were quantified on-line by ICP-MS fitted with a frequency-matching generator allowing a quasi-uniform response over the large (20-90%) acetonitrile mobile phase concentration range. The morphology of HPLC-ICP-MS chromatograms was remarkably similar to that of HPLC multi-ion extracted ESI-MS chromatograms. The detection limits obtained by ICP MS and ESI MS were 1 and 2ppb, respectively.

Direct sensitive simultaneous determination of fluorinated benzoic acids in oil reservoir waters by ultra high-performance liquid chromatography-tandem mass spectrometry.

A direct ultra-high performance reverse-phase HPLC (UHPLC)--electrospray MS/MS method was developed for the simultaneous determination of 16 fluorinated benzoic acids (FBAs) in oil reservoir waters. The separation was achieved within 5 min in a non-linear gradient mode using a 1-ml sample aliquot. The method detection limits were in the lower ng/ml range (between 0.05 and 50 ng/ml, depending on the compound) owing to the use of the travelling-wave collision cell technology. The method developed was more sensitive, faster (by avoiding sample preconcentration and purification steps) and more robust than the GC/MS methods currently used in oil industries. The accuracy of the method was verified by comparison with GC/MS results. It was applied to the determination of FBAs in water samples coming from reservoir tracing campaigns.