| Abstract
| - A direct enzyme-linked immunosorbent assay for thedetection of the short-chain sulfophenylcarboxylic acids(SPCs), the main metabolites of the linear alkylbenzenesulfonates, is reported. Six SPCs (2C3, 2C4, 3C4, 2C5,3C5, 3C6), differing in the length of the alkyl chain(between C3 and C6) and in the position of the phenylsulfonic group versus the carboxylic group, have beensynthesized. Antibodies have been raised against a mixture of the corresponding horseshoe crab hemocyaninconjugates prepared by coupling the carboxylic acid to thelysine amino acid residues. The immunoassay As115/3C4−HRP achieves an IC50 value of 23 nM (6.67 μg L-1)and a detection limit of 0.85 nM (0.24 μg L-1), using asstandard analyte an equimolar mixture of the six SPCs.The immunoassay has found to work better in media withlow or moderate ionic strength (4−30 mS cm-1). Thedecrease in the detectability produced by the potentialformation of SPC salts with divalent cations such as Ca2+can be prevented by lowering the pH of the assay mediumbelow the pKa value of the SPC carboxylic group and usinga buffer chelating with properties such as citrate buffer.The assay can be considered specific for short-chain SPCssince congeners with longer alkyl chains and other pollutants containing sulfonic groups in their structure donot interfere significantly in the assay. Preliminary experiments addressed to evaluate the potential application ofthis assay to environmental water samples demonstratethe usefulness of the assay.
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