RAPID SCREENING METHOD FOR DITALLOWDIMETHYLAMMONIUM CHLORIDE AT THE LOW PPB LEVEL IN SURFACE-WATER USING SOLID-PHASE EXTRACTION AND NORMAL-PHASE LIQUID-CHROMATOGRAPHY WITH ONLINE POSTCOLUMN ION-PAIR EXTRACTION AND FLUORESCENCE DETECTION

A rapid high-performance liquid chromatographic screening method for ditallowdimethylammonium chloride (DTDMAC) in surface water is described. Sample preparation involves solid phase ''traction of DTDMAC from 25 ml surface water. Analysis is carried out by normal-phase liquid chromatography coupled on-line with post-column ion-pair formation, with 9, 10-dimethoxyanthracene-2-sulphonate (DAS) as the fluorescence extraction reagent. A reaction coil is used to extract the aqueous reagent from the organic/aqueous effluent. Two phase separators, connected in series, separate the aqueous and the organic phase. The organic phase is monitored using a fluorescence detector operated at excitation and emission wavelengths of 384 and 452 nm, respectively. Using this procedure, the recovery of DTDMAC from samples spiked at the 4.9 ppb level was 21+/-3.4%, and at the 9.8 ppb level 42+/-4% (n=5). DTDMAC can be monitored in surface water samples with a limit of determination of 5 ppb (mug/l).