Determination of alcohol sulfates and alcohol ethoxysulfates in wastewater samples by liquid chromatography tandem mass spectrometry

Abstract

The work develops a liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for the identification and quantification of alkyl homologues of alcohol sulfates (AS) and ethoxymers of alcohol ethoxysulfates (AES) in wastewaters. The method involves isolation and preconcentration of the analytes from the samples using solid-phase extraction (SPE) with SAX cartridges prior to their quantification by LC–MS/MS with electrospray (ESI) interface in negative mode. The limits of detection (LOD) found were 0.1μgL−1 for AS, and ranged from 0.2 to 0.5μgL−1 for AES. The limits of quantification (LOQ) ranged from 0.3 to 0.4μgL−1 for AS, and from 0.5 to 1.5μgL−1 for AES. The accuracy of the method was studied in terms of trueness and precision. Trueness was evaluated by using a spike recovery assay with spiked blank samples. Recoveries ranged from 96.0 to 102.8% for AS and from 93.4 to 105.1% for AES. Precision (in terms of inter- and intra-day RSD) was lower than 5% for AS and AES. Finally, the method was satisfactorily applied to the quantification of compounds in wastewater samples collected from a wastewater treatment plant (WWTP) located in the city of Granada (Spain). Data obtained showed that AS are present in concentration levels from 0.7 to 39.4μgL−1 in influent waters and from 1.1 to 8.1μgL−1 in effluent waters. As for AES, the amounts (sum of ethoxymers) found ranged from 0.7 to 24.0μgL−1 in influents and from 1.9 to 2.5μgL−1 in effluents.