On-line continuous-flow extraction system in liqud chromatography with ultraviolet and mass spectrometric detection for the determination of selected organic pollutants

An on-line extraction system with completely continuous-flow analysis prior to the liquid chromatographic (LC) column was used for the determination of the organophosphorus pesticides tetrachlorvinphos and parathion-methyl and their degradation products 2,4,5-trichlorophenol and 4-nitrophenol, respectively, and the chlorinated phenoxy acids 2,4-D, 2,4,5-T and silvex in water samples. The extent of extraction varied from 100% for chlorinated phenoxy acids to 60% for organophosphorus pesticides and 2,4,5-trichlorophenol. The extraction of 4-nitrophenol was less than 10% under these conditions. By employing positive-ion mode thermospray LC-mass spectrometry, the characterization of tetrachlorvinphos was feasible, indicating [M + NH₄]⁺ as the base peak and a second peak with 20% relative intensity corresponding to [M + H]⁺. When the negative-ion mode was used, the chlorinated phenoxy acids and 2,4,5-trichlorophenol exhibited [M + HCOO]^? as the base peak and a second peak with 30% relative intensity corresponding to [M ? H]^?. The determination of 1 mg l^?1 of tetrachlorvinphos spiked in a surface water sample is reported.