Determination of Alkylbenzyldimethylammonium Chlorides in River Water and Sewage Effluent by Solid-Phase Extraction and Gas Chromatography/ Mass Spectrometry

This study presents a modified method to analyze alkylbenzyidimethylammonium chlorides (ABDACs) in river water and sewage effluent The method involves mixed samples with linear alkylbenzenesulfonates (LAS) as a counterion to enhance the extraction of ABDAC residues from an RP-18 solid-phase cartridge by formation of hydrophobic ion-pair complexes. The ABDACs were then eluted with methanol-ethyl acetate (1:1, v/v) and formed to their corresponding alkyldimethylamines by the Hofmann degradation with potassium tert-buboxide. The alkyldimethylamines were then identified and quantitated by gas chromatograph/mass spectrornetry (GC/MS). The results indicate that, in the presence of LAS, debenzylation of ABDACs occurs selectively at a temperature higher than 90 °C to produce the corresponding nonionic alkyldimethylamines. The method proposed herein provides a high precision and sensitivity for ABDACs, to quantitation at <0.1 mug/L in 500 mL of the water samples. The average recovery of ABDAC spiked water samples was 95% with relative standard deviations (RSD, n = 7) of 9%. The RSDs of three replicate environmental sample analyses ranged from 5 to 11%. Direct HPLC method was applied to evaluate the GC/MS method, and compatible results were observed.