Pesticides in seaweed: optimization of pressurized liquid extraction and in-cell clean-up and analysis by liquid chromatography-mass spectrometry.

Chemical residues, such as insecticides and anthelmintics, are frequently redistributed from the aquatic environment to marine species. This work reports on a fast validated protocol for the analysis of azamethiphos, three avermectins, two carbamates and two benzoylurea pesticides and chemotherapeutic agents in seaweeds based on pressurized liquid extraction and separation of analytes by liquid chromatography coupled with tandem mass spectrometry. The variables affecting the efficiency of pressurized liquid extraction, including temperature, number of extraction cycles, static extraction time and percent acetonitrile flush volume, were studied using a Doehlert design. The optimum parameters were 100 °C and one cycle of 3 min with 70 % acetonitrile. Adequate in-cell clean-up of the seaweeds was achieved using 0.8 g of Florisil over 0.1 g of graphitized carbon black on the bottom of the cell. The optimized method was validated using an analyte-free seaweed sample fortified at different concentrations. The limits of quantification ranged from 3.6 µg kg(-1) (azamethiphos) to 31.5 µg kg(-1) (abamectin). The recovery was from 87 to 120 % in most cases at different spiking levels. Finally, the reproducibility of the method expressed as the relative standard deviation and evaluated at concentrations of 10 and 50 µg kg(-1) was in the range 9-14.3 % and 6.1-12.3 %, respectively. The applicability of the method was evaluated with five commercial and 12 wild edible seaweeds, and four target compounds were detected in two wild seaweeds at a concentration below the quantification limit.

Dispersive liquid-liquid microextraction coupled with programmed temperature vaporization-large volume injection-gas chromatography-tandem mass spectrometry for multiclass pesticides in water.

A simple solvent-less procedure for the determination of seventeen pesticides and related compounds in environmental water and wastewater using dispersive liquid-liquid microextraction (DLLME) coupled with gas chromatography-mass spectrometry in tandem (GC-MS/MS) with large-volume injection, having a programmed temperature vaporizer (PTV-LVI), is described. The parameters affecting the extraction efficiency of the target analytes from water samples were systematically investigated. A response surface Doehlert design was used. The best extraction conditions involved a rapid injection of a mixture of 1.9 mL of acetonitrile (as a dispersant) and 178 µL of trichloroethane (as an extractant) into 10 mL of water placed in a conical bottom glass tube. After manually shaken for 3.0 min and centrifugation at 3600 rpm (5 min), 50 µL of the sedimented phase was directly injected into the PTV-LVI-GC-MS/MS system. The limits of quantitation (LOQs) ranged from 0.5 to 18 ng L⁻¹ for all pesticides, except empentrin (132 ng L⁻¹). The relative standard deviations (RSDs) for the analytes ranged between 0.8 and 14.6% for both intraday and interday precision. Accuracy, expressed as the mean extraction recovery, was between 70 and 130%. Using the internal standard method and surrogate deuterated standards, the total concentration of pesticides was in the range from 2.7 to 440 ng L⁻¹ in seawater, river water and sewage water.

Determination of chloropropanols in foods by one-step extraction and derivatization using pressurized liquid extraction and gas chromatography-mass spectrometry.

3-Chloropropane-1,2-diol (3-MCPD) and 1,3-dichloro-2-propanol (1,3-DCP) were determined for the first time in bakery foods using pressurized liquid extraction (PLE) combined with in situ derivatization and GC-MS analysis. This one-step protocol uses N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) as silylation reagent. Initially, screening experimental design was applied to evaluate the effects of the variables potentially affecting the extraction process, namely extraction time (min) and temperature (°C), number of cycles, dispersant reagent (diatomaceous earth in powder form and as particulate matter with high pore volume Extrelut NT) and percent of flush ethyl acetate volume (%). To reduce the time of analysis and improve the sensitivity, derivatization of the compounds was performed in the cell extraction. Conditions, such as the volume of BSTFA, temperature and time for the in situ derivatization of analytes using PLE, were optimized by a screening design followed to a Doehlert response surface design. The effect of the in-cell dispersants/adsorbents with diatomaceous earth, Florisil and sodium sulfate anhydrous was investigated using a Box-Behnken design. Using the final best conditions, 1 g of sample dispersed with 0.1 g of sodium sulfate anhydrous and 2.5 g diatomaceous earth was extracted with ethyl acetate. 1 g of Florisil, as clean-up adsorbent, and 70 µL of BSTFA were used for 3 min at 70°C. Under the optimum conditions, the calibration curves showed good linearity (R(2)>0.9994) and precision (relative standard deviation, RSD≤2.4%) within the tested ranges. The limits of quantification for 1,3-DCP and 3-MCDP, 1.6 and 1.7 µg kg(-1), respectively, are far below the established limits in the European and American legislations. The accuracy, precision, linearity, and limits of quantification provided make this analytical method suitable for routine control. The method was applied to the analysis of several toasted bread, snacks, cookies and cereal samples, none of which contained chloropropanols at concentrations above the legislation levels.