Thermospray liquid chromatography-mass spectrometry can be used for identifying and determining both paraquat (C12H14N2+2) and diquat (C12H12N2+2). Reversed-phase liquid chromatography was performed using a 15-cm Shim-pack CLCODS column, with methanol-water (80-20) + 0.1 M ammonium acetate (adjusted to pH 5 with trifluoroacetic acid) as buffers, at a flow-rate of 1.0 ml/min. The mass spectral sensitivity was best when the temperatures of the vaporizer, block and tip heater of the ion source block were set at paraquat and diquat, respectively. Detection limits by selected ion monitoring were of the order of 20 ng (S/N = 3.5). The mass spectra are influenced by temperature and therefore, precise temperature contorl is essential. © 1993.
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