Method validation and environmental monitoring of triethanolamine ester quaternary ammonium compounds.

In this study water and sediment samples, collected from the River Nene (Northamptonshire) at several sites in the vicinity of the Great Billing sewage treatment plant (STP), were analysed for triethanolamine quaternary compounds (TEAQ, ester quats). A method was developed using liquid chromatography tandem mass spectrometry (LC/MS/MS) with a electrospray ionisation source (ESI). Ten components were determined using a characterised commercial sample of Tallow TEAQ as a standard. To our knowledge this is the first time environmental concentrations of a wide spectrum of individual homologues of TEAQ have been reliably quantified covering a broad range of environmental matrices (STP influent, STP effluent, surface waters and sediments), due to the challenging nature of the analytical method. The method featured novel solutions for the determination of long and multiple chain length alkyl quats, controlling loss processes, background contamination and chromatographic performance. TEAQ compounds were found to be highly removed in the sewage treatment plant resulting in low effluent concentrations. Low concentrations in both river water and sediment samples were found also. In many cases levels were below the Method Detection Limit (MDL). In river water samples, mean values of TEAQ compounds found were 210-398 ng/L for C16:0/C18:0 TEAQ diester and 126-287 ng/L for C18:0/C18:0 TEAQ diester. River sediment was found to contain mean TEAQ levels of 7.07-12.5, 19.7 to 40.3 and 7.04-35.1 µg/kg dry weight for C16:0/C16:0, C16:0/C18:0, and C18:0/C18:0 TEAQ, respectively. At Great Billing STP monoesters and diesters of TEAQ were shown to be efficiently removed (>97 and 99 %, respectively), although limited samples were taken on this occasion.

Monitoring and modelling of siloxanes in a sewage treatment plant in the UK.

Monitoring of cyclic volatile methylsiloxanes (cVMS) carried out at Anglian Water's Broadholme sewage treatment plant (STP) is described. The method deployed used headspace gas chromatography/mass spectrometry (HS-GC/MS) and the addition of isotopically labelled cVMS to correct for partitioning in samples containing high levels of particulate and dissolved organic carbon. The method was capable of measuring cVMS in raw sewage samples, with recoveries of 80%, 85% and 71% respectively, for D4, D5 and D6. The limit of quantification was 0.2µgL(-1) for all three substances. Recoveries close to 100% were observed for all cVMS spiked into treated effluent (LOQ=0.01µgL(-1)). Despite the volatile nature of cVMS and its ubiquitous presence in the ambient atmosphere, the methods deployed showed excellent recoveries, reproducibility and quantification limits. A distinct diurnal variation in cVMS concentration, probably linked with the use of personal care products was observed for raw sewage but not in treated sewage effluent. The estimated per capita consumption of D5 (∼2.7mgcap(-1)d(-1)) derived for the population served by this plant was significantly lower than that derived in the Environment Agency (UK) risk assessment (11.6mgcap(-1)d(-1)). The cVMS were highly removed during sewage treatment with efficiencies greater than 98%. The methods and findings of this pilot study can be used as the basis for future studies on the fate of cVMS substances in STPs.

Determination of decamethylcyclopentasiloxane in river and estuarine sediments in the UK.

Robust analytical procedures for the measurement of decamethylcyclopentasiloxane (D5) in river and estuarine sediments and their application in determining environmental concentrations in the UK are presented for the first time in this work. Novel approaches to minimise commonly reported artefacts are utilised, improving the confidence in the concentrations of D5 reported. Accelerated solvent extraction (ASE) and liquid-solid extraction methods are compared. Both methods use on-column injection gas chromatography/mass spectrometry (GC/MS). Measurements of D5 concentrations in sediments sampled from the river Great Ouse and from the Humber estuary (UK) are also reported. ASE was suitable to measure concentrations of D5 in sediments obtained from the river Great Ouse, UK (186-1450 ng g⁻¹, dry weight) and octamethyltetracyclosiloxane (D4, 12-24 ng g⁻¹, dry weight). C12 linear alkybenzene (C12 LAB), which can be used as a chemical marker for sewage effluent related emissions, was also measured in this analysis. Liquid-solid extraction was optimised to provide more confidence in the lower D5 concentrations measured in the Humber estuary, UK (49-256 ng g⁻¹, dry weight). A Limit of quantitation (LOQ) for D5 of 57-110 and 4 ng g⁻¹ dry weight was determined for ASE and liquid-solid extraction, respectively.