Multi-residue method for the analysis of commonly used commercial surfactants, homologues and ethoxymers, in marine sediments by liquid chromatography-electrospray mass spectrometry

A simple, sensitive and accurate multi-residue method has been developed for simultaneous determination of the main types of surfactants (linear alkylbenzene sulfonates [LAS], alkyl sulfates [AS], alkyl ethoxysulfates [AES], and alcohol polyethoxylates [AEO]). Ultrasound-assisted extraction was used for the extraction of surfactants. Liquid chromatography with tandem mass spectrometry with an electrospray interface (LC-ESI-MS/MS) was used for identification and quantification of the target compounds. The mass spectrometric conditions in positive and negative ionization mode were individually optimized for each analyte to obtain the maximum sensitivity. The selection of specific fragmentation reactions for LAS, AS and AES allowed simultaneous quantification and identification in one run, ensuring the high specificity of the method. For AEO determination, the triple quadrupole mass spectrometer was operated in the Q1 multiple ion mode (Q1 MI) with positive ionization due to the absence of fragmentation. The analytes were separated in less than 15 min. The limits of detection found ranged from 0.02 to 7.00 μg kg− 1 in marine sediments. Due to the absence of certified materials, the method was validated using matrix-matched calibration and a recovery assay with spiked samples. Recovery rates were close to 100% in all cases and ranged from 94.1% to 113.3%. Precision was also evaluated in terms of %RSD. The values obtained, expressed as inter-day variability, fell between 2.0% and 8.2% for all the analyzed surfactants. Finally, after validation, the proposed method was applied for the simultaneous determination of all the target compounds in samples taken from Tenerife Island, Spain. For each family of analyzed compounds, the homologues or ethoxymers found at the highest concentration levels were LAS C13, AS C16, AES C14 EO1 and AEO C18 EO14 with values up to 1136, 130, 61 and 9.4 μg kg− 1 respectively.