DETERMINATION OF CHLOROPHENOXY ACIDS USING HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY PARTICLE BEAM MASS-SPECTROMETRY

An isocratic mobile phase of methanol containing phenoxyacetic acid-dilute acetic acid (70:30) achieved a good high-performance liquid chromatographic (HPLC) separation of 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) and 2-(2,4,5-trichlorophenoxy)propionic acid (Silvex). The HPLC eluate was introduced into a mass spectrometer operated under methane-enhanced electron-capture negative ionization conditions through the particle beam interface. With the mass spectrometer operated in selected-ion monitoring mode, detection limits in the low mu-g/l range were attained for all three acids. This is one of the first reports of liquid chromatography coupled with mass spectrometry through the particle beam interface for the detection of chlorophenoxy acid herbicides.