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 EXTRACTIONAND FLUORESCENCE DETECTION

A rapid high-performance liquid chromatographic screening method for d itallowdimethylammonium chloride (DTDMAC) in surface water is describe d. Sample preparation involves solid phase ''traction of DTDMAC from 2 5 ml surface water. Analysis is carried out by normal-phase liquid chr omatography coupled on-line with post-column ion-pair formation, with 9, 10-dimethoxyanthracene-2-sulphonate (DAS) as the fluorescence extra ction 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 proce dure, 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 m onitored in surface water samples with a limit of determination of 5 p pb (mug/l).