A new method for the routine analysis of LAS and PAH in sewage sludge by simultaneous sonication-assisted extraction prior to liquid chromatographic determination

Abstract

Linear alkylbenzene sulphonates (LAS) and polycyclic aromatics hydrocarbons (PAH) are organic pollutants in sewage sludge which will have to be monitored in the European Union according to the third draft of a future sludge directive. In the present work, an analytical method for the simultaneous extraction of 4 LAS homologues and 16 PAH congeners in sludge from wastewater treatment plants is proposed to improve the routine analysis of these compounds in sludge samples. The method involves sonication assisted extraction, clean-up and preconcentration by solid phase extraction, and determination by high-performance liquid chromatography with ultraviolet diode array (UV-DAD) and fluorescence (FLD) detectors. Average recoveries were 87% for LAS and 76% for PAH, with relative standard deviations below 13%. Limits of quantification of LAS and PAH were in the range from 13 to 56 mg kg −1 and from 80 to 650 μg kg −1, respectively, when using UV-DAD. Limits of quantification of LAS and PAH were in the range 5–18 mg kg −1 and from 1 to 150 μg kg −1, respectively, when using FLD. The applicability of the proposed method was evaluated by the determination of these compounds in sludge from wastewater treatment plants in Seville (South Spain).