Ultrasonic extraction and LC determination of linear alkylbenzene sulfonate in plant tissues

A new method has been developed for the extraction and determination of linear alkylbenzene sulfonate (LAS) in plant tissues (rice stems and leaves). It consists of methanol-ultrasonic extraction followed by clean-up with aluminum oxide, enrichment with C-18 solid-phase extraction column and determination by HPLC. Both efficiency and accuracy of the overall method were high, i.e. mean recovery of: 89 % (84 to 93 % for LAS concentrations ranging from 1 to 100 mg kg(-1)) and repeatability of: 3 % relative standard deviation for 6 replicate analyses. With a 2 g sample for analysis, LAS levels of 0.5 mg kg(-1) in plants could be detected with the proposed method. Further advantages were: it was less time consuming (1 h for extraction), less solvent consumption, and smaller samples (2 to 3 g) required when compared with Soxhlet extraction.