Extraction and isolation of linear alkylbenzenesulfonate and its sulfophenylcarboxylic acid metabolites from fish samples

Linear alkylbenzenesulfonate (LAS) is the most widely used synthetic surfactant. In fish, assessment of the environmental risk and investigation of the biotransformation behavior of LAS require compound-specific methods for extraction and isolation of LAS and its biotransformation products, sulfophenylcarboxylic acids (SPC). Matrix solid-phase dispersion (MSPD) extraction with subsequent ion-pair liquid-liquid (IP-LL) partitioning of the extract was a time-efficient sample preparation method for analysis of LAS. The recovery of parent LAS from spiked fish exceeded 70%, and the limit of quantitation ranged around 0.2 mg.kg-1 corresponding to 0.6 mumol.kg-1. In a simultaneous determination of LAS and SPC in fish, the analytes were MSPD extracted in different fractions. The target compounds were separated from the sample matrix by protein precipitation and subsequent isolation of (a) SPC by graphitized carbon black solid-phase extraction of the supernatant and (b) parent LAS by IP-LL partitioning of the pellet obtained after protein precipitation. The recoveries of the model compounds C12-2-LAS and C4-3-SPC were 84 +/- 6 and 65 +/- 11%, respectively. The use of C3-3-SPC as an internal standard corrected for the loss of the biotransformation product during sample workup. The suitability of both methods was demonstrated by analyzing fish containing LAS and SPC incurred during aqueous exposure.