Ion-pair extraction and GC–MS determination of linear alkylbenzene sulphonates in aqueous environmental samples

A GC–MS method was developed for the determination of linear alkylbenzene sulphonates (LAS) and sulphophenylcarboxylic acids (SPC) in aqueous environmental samples. LAS and SPC were isolated from aqueous samples using methylene green (MG) as ion-pair reagent and derivatised with diazomethane for their chromatographic analysis. LAS and SPC were then analysed with GC–MS in EI mode as their methyl esters. The method eliminates positive and negative interferences found by the methylene blue method and considered to be selective and sensitive for the determination of LAS and SPC in aqueous samples. The recovery of LAS was 98% with a relative standard deviation (R.S.D.) of 2.0% and the detection limit obtained from calculations by using GC–MS results based on S/N:3 was lower than 10 ppb. Obtained results revealed that the method can also be employed in the analysis of organic compounds bearing sulphate and sulphonate groups.