Determination of linear alkyl benzene sulfonates in vegetable by modified QuEChERS coupled to liquid chromatography-tandem mass spectrometry

Linear alkyl benzene sulfonates (LASs) with alkyl chains from C₁₀ to C₁₄ are the most commonly used anionic surfactants in household laundry. However, LAS toxicity toward agricultural soil further could be formed at a risk for fruits and vegetables grown on the land, so that to develop a sensitive and precise analytical technique for determination of trace residual sulfonates in vegetables is very important for health. This study developed a QuEChERS extraction coupled to liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for analyzing LASs in vegetables and fruits. The best results were obtained using acetonitrile as the extraction solvent combined with 25 mg primary secondary amine and 25 mg graphitized carbon black as sorbents. The linearity ranged between 1 and 250 ng/mL as well as limit of quantification (LOQ) was obtained in the range of 0.01–0.23 ng/mL of the proposed analytical method. The proposed method was utilized to detect the real spinach samples and water spinach planted with LASs-spiked water, and the results showed the trace LASs were detected with concentration between 1.8 and 29.1 ng/g. In this study, a thorough optimization and validation of different amount of sorbent cleanup efficiency approaches was performed for the first time for the analysis of LAS.