Determination of alcohol ethoxylates in environmental samples using derivatisation and LC/MS

Sparham, Christopher John (2006) Determination of alcohol ethoxylates in environmental samples using derivatisation and LC/MS. Doctoral thesis, Northumbria University.

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Abstract

A new method for the analysis of alcohol ethoxylates (AEs) using liquid chromatography with electrospray ionisation mass spectrometry (LC/ESI-MS) is described. The procedure in. corporates a novel derivatisation step with phthalic anhydride for the analysis of E00_,o ethoxylates in a single analysis. The derivatives obtained have proved to be very stable and the negative ion spectra show reduced background ions and competing adduct formation as compared to positive ion spectra. An automated solid phase extraction (SPE) step is used to allow both pre- concentration and clean-up of the environmental samples. The addition of 40 % v/v methanol prior to loading samples provides more efficient recovery of AEs across the C12 to C18 range than previously reported in the literature, reducing hydrophobic losses. Recoveries from final effluent spiked at 100 pg/L total AE, for the 126 species analysed, were found to be in the range 55 — 117%, with approximately 100 of the individual analytes having recoveries of 90 —105 %. A method detection limit of 0.02 iig/L for individual ethoxylate components is reported with the instrument operated in scan mode over the range m/z 300 to 1300. The method was applied to sewage effluent and influent samples, with AEs determined at approximately 7 and 5000 µg/L, respectively, indicating efficient removal of AEs in the sewage treatment plant. The AEs in the final effluent consisted primarily of fatty alcohols (FAs). Similar optimisation in the extraction of sediment and sludge samples was carried out with ultrasonic, Soxhlet and accelerated solvent extraction (ASE) methodology being compared. The most efficient technique was ASE, which was then used to analyse an activated sludge sample, where again. significantly high levels of FAs, compared to other AEs, were found in the sample. This data and the final effluent data are consistent with other current monitoring data for AEs and show the importance of a method capable of extracting and ionising the free alcohol efficiently. The AE fingerprint during biodegradation studies was also accurately determined giving elucidation of mechanisms of primary degradation. Linear and branched AEs were investigated with metabolite identification also carried out for the linear AE. Biodegradation of native AEs present in sewage influent was also studied in direct discharge scenarios to aid in. risk assessment in situations where sewage treatment is absent.

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