Forensic toxicological determination of surfactant by liquid chromatography/electrospray ionization mass spectrometry and liquid chromatography/electrospray ionization tandem mass spectrometry

Abstract

A procedure for identifying surfactants was investigated by liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) and liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) from the forensic toxicological point of view. The analysis of anionic, cationic, and nonionic surfactants in both negative and positive mode revealed that anionic and cationic surfactants are detected as M- ions in the negative mode and M+ ions in the positive mode, respectively, while [M+H]+ ions or [M+NH4]+ ions appeared for nonionic surfactants in the positive mode. Anionic surfactants (linear alkylbenzene sulfonate and polyoxyethylene alkyl ether sulfate) were successfully extracted using a weak anion exchange cartridge, with recovery rates of 53.8-76.7%. Cationic surfactant (benzalkonium) was also easily extracted using a weak cation exchange cartridge with a recovery rate of 107%. When aqueous solutions of cationic, anionic, and nonionic surfactants were concentrated to dryness, the recovery rates ranged from 65.8% to 124%. By analyzing anionic surfactants (alpha-olefine sulfate, polyoxyethylene alkyl ether sulfate, and linear alkylbenzene sulfonate) in the product ion scan mode in LC/ESI-MS/ MS, it was possible to identify the structure of the hydrophilic group of surfactants, and MS/MS was confirmed to be a powerful technique for classification.