New sample treatment for determination of linear alkylbenzene sulfonate (LAS) in agricultural soils by liquid chromatography with fluorescence detection

Abstract

A new sample-treatment procedure has been developed for determination of total linear alkylbenzene sulfonate (LAS), i.e. homologues and isomers, in agricultural soil. The procedure involves two steps, ultrasound-assisted extraction of LAS from the samples with methanol then clean-up of the methanolic extracts and preconcentration of the LAS by solid-phase extraction on two adsorbent cartridges (SAX and C18). The ultrasound-assisted procedure reduces extraction time (10 min in contrast with 6-12 h for conventional Soxhlet extraction) and requires only small volumes of organic solvent. The effect of different variables interacting in the ultrasound-assisted extraction process was studied. Finally, separation and quantification of the homologues and isomers of LAS was performed by liquid chromatography with fluorescence detection (LC-FD). 2-Octylbenzenesulfonic acid sodium salt (Na-2ØC8-LAS) was used as internal standard. The proposed method was satisfactorily used for determination of LAS in agricultural soil samples from the fertile plain of Granada (Spain).

Determination of sulfophenyl carboxylic acids in agricultural groundwater samples by CE with ultraviolet absorption detection

“…Previously, a study about the determination of LAS in the soil of the plot selected was carried out at different depths (surface, 10, 20, 30, 40, 50, and 60 cm) using the method developed by Nimer et al [35]. The achieved results confirmed that these soil samples were free of LAS.…”

“…This fact combined with others studies focused on the determination of LAS in both soil and groundwater (at different depths) [35,36] could be considered as an experimental demonstration that LAS are practically biodegraded before reaching the saturated zone of the aquifer. Apparently, presumably no contamination by LAS occurs when the agricultural soil is irrigated with wastewater containing LAS.…”

Matrix effect study in the determination of linear alkylbenzene sulfonates in sewage sludge samples

“…We followed a methodology proposed by our research group that has already been published [11]. Briefly, a volume of 100 ml methanol was used as extraction solvent, extraction time was 10 min, and amplitude of 75% and power of 4,000 rpm (2,360 g) were set.…”

“…Nevertheless, these methodologies present several disadvantages, such as the high extraction time for Soxhlet (8-24 h) or the large volumes of solvents needed ($200 ml for Soxhlet and 50-150 ml for ultrasound). Modern extraction procedures such as pressure liquid extraction (PLE) [7,15,20,22], microwaveassisted extraction (MAE) [12,30], supercritical fluid extraction (SFE) [31], or ultrasonic extraction [11,32] are being used as alternatives because of their high efficiency within shorter extraction times (5-10 min) and the lower solvent volume needed (5-20 ml). However, some of these methodologies are tedious, time consuming, and require one or two solidphase extraction (SPE) steps for concentration and cleanup of samples.…”

“…For sample treatment, the Soxhlet technique [5][6][7]14,18,28] and ultrasonic extraction [10,11,29] have been widely used in the determination of LAS in environmental samples. Nevertheless, these methodologies present several disadvantages, such as the high extraction time for Soxhlet (8-24 h) or the large volumes of solvents needed ($200 ml for Soxhlet and 50-150 ml for ultrasound).…”