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 C_16:0/C_18:0 TEAQ diester and 126-287 ng/L for C_18:0/C_18:0 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 C_16:0/C_16:0, C_16:0/C_18:0, and C_18:0/C_18:0 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.