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 alkylbenzyldimethylammoniu m chlorides (ABDACs) in river water and sewage effluent. The method involve s mixed samples with linear alkylbenzenesulfonates (LAS) as a counterion to enhance the extraction of ABDAC residues from an RP-18 solid-phase cartrid ge by formation of hydrophobic ion-pair complexes. The ABDACs were then elu ted with methanol-ethyl acetate (1:1, v/v) and formed to their correspondin g alkyldimethylamines by the Hofmann degradation with potassium tert-butoxi de. The alkyldimethylamines were then identified and quantitated by gas chr omatograph/mass spectrometry (GC/MS). The results indicate that, in the pre sence of LAS, debenzylation of ABDACs occurs selectively at a temperature-h igher than 90 degreesC to produce the corresponding nonionic alkyldimethyla mines. The method proposed herein provides a high precision and sensitivity for ABDACs, to quantitation at less than or equal to0.1 mug/L in 500 mt 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 wer e observed.