Trace determination of linear alkylbenzene sulfonates: application in artificially polluted soil-carrots system

Abstract

Surfactants are widely used in household and industrial products. The risk of incorporation of linear alkylbenzene sulfonates (LAS) from biosolids, wastewater, and fertilizers land application to the food chain is being assessed at present by the European Union. In the present work, a complete analytical method for LAS trace determination has been developed and successfully applied to LAS (C10-C13) uptake in carrot plants used as model. These carrots were grown in soil with the trace organics compounds added directly into the plant containers in pure substances form. LAS trace determination (mug kg(-1) dry matter) in carrots samples was achieved by Soxtec apparatus and high-performance liquid chromatography-fluorescence detection. The methodology developed provides LAS determination at low detection limits (5 mug kg(-1) dry matter) for carrot sample (2 g dry matter) with good recoveries rate (>90%). Transfer of LAS has been followed into the various parts of the carrot plant. LAS are generally found in the carrot leaves and percentage transfer remains very low (0.02%).

Figure 1

General chemical structure of linear alkylbenzene sulfonate (LASs), where x and y corresponds with the number of CH² on each side of the benzene sulphonate group (7 • x + y • 10).

Figure 2

Description of the different treatment stages for LASs quantitative determination.

Figure 3

HPLC-FLD chromatogram obtained for carrot sample spiked with LASs (50 μgg⁻¹ dry matter). Chromatographic condition: Inertsil ODS3 colum of 250 × 4.6 mm (5 μg), flow rate = 1.5 mL min⁻¹, fluorescence detection (ex: 225 nm–em: 305 nm), 20 μL of injection volume.