Rapid liquid chromatography–tandem mass spectrometry-based method for the analysis of alcohol ethoxylates and alkylphenol ethoxylates in environmental samples

Abstract

A sensitive and selective method for the determination of alcohol ethoxylates (AEOs) and alkylphenol ethoxylates (APEOs) using solid-phase extraction (SPE) and LC–MS/MS was developed and applied to the analysis of water samples. All AEO and APEO homologues, a total of 152 analytes, were analyzed within a run time of 11min, and the MS allowed for the detection of ethoxymers containing 2–20 ethoxy units (nEO=2–20). The limits of detection (LOD) were as low as 0.1pg injected, which generally increased as nEO increased (e.g., as high as 300pg for nEO=20). Additionally, the responses of the various ethoxymers varied by orders of magnitude, with ethoxymers with nEO=3–5 being the most sensitive and those with nEO>15 producing the least response in the MS. Absolute extraction recoveries of the analytes ranged from 37% to 69% in ultrapure water (RSD≤20%), with the recovery depending on the length of the alkyl chain. Abiotic stability studies were performed, and C14–18 ethoxylates showed significant degrees of degradation. Water samples from the Colorado River were then analyzed for AEOs and APEOs, with absolute extraction recoveries ranging from 33% to 45% (RSD≤12%). The predominant species observed in most samples were the octylphenol (OP) and nonylphenol (NP) ethoxylates, which contained total concentrations that were greater than 100ng/L APEOs in a couple samples. Other AEO homologues were identified in the river water samples, including C13, C15, C16, and C18 ethoxylates, but these compounds were generally present at much lower levels (i.e., <50ng/L total concentration).