Determination of polycyclic aromatic sulfur heterocycles in ascidians (Phallusia nigra) using a green procedure

Ascidians as a pollution bioindicator are well reported based on metal analysis, but little is known about organic compounds accumulation in these marine organisms. In this study, a miniaturized solid-liquid extraction method, combined with dispersive micro-solid-phase extraction (MSLE-D mu SPE) cleanup was applied to the determination of fourteen polycyclic aromatic sulfur heterocycles (PASH) from petrochemical sources in ascidian Phallusia nigra. The alumina amount in D mu SPE step was optimized and the method was validated in terms of linearity, accuracy and precision using matrix-matched calibration. The ascidians were collected in Todos os Santos Bay, in a region close to a floating gas station. In the laboratory, samples were dissected in two parts (branchial basket and tunic), lyophilized, weighed and extracted by MSLE-D mu SDE. Analytes were determined by gas chromatography coupled to mass spectrometry in selective ion monitoring (GC-MS/SIM). Under optimum conditions, the limit of detection ranged from 0.17 mu g L-1 (4,6-dimethyldibenzothiophene) to 1.99 mu g L-1 (2,3-dimethylbenzothiophene) and the limit of quantification the values were in the range from 0.57 mu g L-1 to 6.65 mu g L-1 for the same compounds. Determination coefficients (R2) >= 0.99 were obtained for all analytical curves. The recoveries of the PASH were between 76 and 119 % with intraday and interday precisions lower than 20 %. The method was successfully applied to ascidian samples and ten PASHs were quantified with highest concentrations in the branchial basket. This study represents the first application of a green miniaturized procedure to the determination of PASH from petrochemical source in marine organisms.

Automated summary

This study successfully applied a miniaturized solid-liquid extraction method combined with dispersive micro-solid-phase extraction to determine the concentration of fourteen polycyclic aromatic sulfur heterocycles (PASH) in the ascidian Phallusia nigra. The results showed that the method was effective and ten PASHs were quantified, with the highest concentrations found in the branchial basket.