Fate studies of the non-ionic surfactant alkyl glucamide by liquid chromatography/electrospray mass spectrometry

Abstract

Alkyl glucamides (AGs) were analyzed by reversed-phase liquid chromatography (LC) coupled to mass spectrometry with electrospray ionization (ESMS). Analytes were separated according to the chain length of two homologs, C12- and C14-glucamide. Mass spectrometric detection in the positive ion mode exhibited higher overall sensitivity where, apart from fragments, different molecular and quasi-molecular ions were obtained. However, application of the negative ion mode offered advantages in terms of reproducibility and extent of information when analyzing environmental samples. Therefore, a simple and sensitive analytical methodology was developed for the determination of AGs in municipal sewage treatment plant influent and effluent based on solid-phase enrichment, LC separation and negative ion ESMS quantification. After preconcentration of 100 ml of aqueous sample, the recoveries using polymeric LiChrolut EN cartridges exceeded 89%. A quantification limit of 0.1 microg l(-1) was achieved. Studies on the biodegradability and metabolic pathway of C10-glucamide were carried out on a laboratory-scale microbial test unit under aerobic conditions. A postulated metabolism including omega-oxidation of the alkyl chain followed by subsequent beta-oxidations was checked by LC/ESMS. Identification and formation of 'C4-glucamide acid' as a degradation intermediate was confirmed by mass spectrometric studies. Higher homolog acids such as C10-, C8- and C6-glucamide acids, which should be predicted precursors of C4-glucamide acid, and any other metabolites, were not detectable, presumably owing to rapid breakdown.