A solid-phase extraction (SPE) method for ultra-sensitive determination of four lipophilic marine biotoxins in bivalve samples by coupling high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS-MS) was developed. Azaspiracid-2 (AZA2), pectenotoxins-2, spirolide (SPX) and gymnodimine were simultaneously determined by HPLC-MS-MS in a positive multiple reaction monitoring mode. Separation was achieved on a reversed-phase C18 column with an acetonitrile-water gradient containing formic acid. During the analysis, solvent effects on the analytes were eliminated by using 1 : 1 water-methanol as dissolving solvent instead of pure methanol. Matrix effects in post-SPE extract and crude extract were seriously evaluated. Increased matrix effects in post-SPE extract countervailed the concentration purpose to some extent. The limits of detection of the SPE-HPLC-MS-MS method were determined to be in the range of 0.013-0.085 µg kg(-1), and the linear range of the method was in the range of 0.128-55.2 ng mL(-1) for the detected toxins. The proposed method was validated in terms of linearity (matrix-matched standard curves), precision, recovery, repeatability and limits of quantification. The recoveries of fortified samples at three different concentration levels were satisfactory, and the intra- and interday precisions were <7 and 10%, respectively.Several bivalve samples were analyzed to demonstrate the applicability of the proposed method. Different target toxins were detected in different kind of bivalves. Among them, AZA2 and SPX1 were first detected in Chinese shellfish. The levels of detected toxins were below the current European Union regulatory limits.

A method was developed and validated for the simultaneous analysis of 112 pesticide residues in vegetables by gas chromatography coupled with triple quadrupole mass spectrometry (GC-QQQ-MS/MS). It is demonstrated that the optimized conditions could provide a more accurate quantitation and lower limit of quantification of the analysis by dispersive-solid phase extraction (D-SPE) cleanup. The samples were extracted with acetonitrile and toluene (8: 1, v/v), and cleaned up by D-SPE. To every 5 mL extraction solution, 0.8 g MgSO4, 0.05 g graphitized carbon black (GCB), 0.1 g ethylenediamine-N-propyl silyl (PSA) and 0.05 g C18 were added. The extracts were analyzed by GC-QQQ-MS/MS using internal standard method. The recoveries of the 112 pesticides at three spiked levels of 20, 50 and 200 microg/kg were ranged from 53.1% to 138.7%, and among which those of 86 pesticides were from 65.0% to 120.0%. The relative standard deviations (RSD) were less than 12%. The limits of quantifications (LOQs) (signal/noise at 10) were between 1.6 and 13.4 microg/kg. The vegetable samples collected from the market such as garlic chives, cucumber and purple cabbage were analyzed, and the residues of triazophos and fenpropathrin were detected in some of these samples. The method can be applied to the routine analysis for the determination of the 112 pesticides in vegetable samples.

No abstract

No abstract

A novel, simple, sensitive, and efficient method for the speciation of inorganic antimony by dispersive liquid-liquid microextraction (DLLME) combined with graphite furnace atomic absorption spectrometry (GF-AAS) is reported. The method uses a hydrophobic complex of antimony(III) with a new chelating agent, 1,2,6-hexanetriol trithioglycolate, at neutral pH. The complex was extracted into the organic phase, whereas antimony(V) remained in aqueous solution. The concentration of antimony(V) was obtained by subtracting the antimony(III) concentration from the total antimony concentration following the reduction of antimony(V) to antimony(III) by L-cysteine. The pH, extraction and dispersive solvents and volumes, and concentration of 1,2,6 -hexanetriol trithioglycolate were optimized. Under the optimized conditions, the analytical curve was linear from 0.26 to 3.2 micrograms per liter with a limit of detection of 27.0 nanograms per liter for antimony(III). The relative standard deviation was 6.8 percent at 0.52 microgram per liter antimony(III) with an enrichment factor of twenty-six. The method was employed for the speciation of antimony in leaching solution in contact with plastic; and the recoveries in fortified samples were between 94.2 and 118.0 percent.