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CAPILLARY ELECTROPHORESIS-ELECTROSPRAY MASS SPECTRA OF THE HERBICIDES PARAQUAT AND DIQUAT
Citation:
Song, X. AND W. Budde. CAPILLARY ELECTROPHORESIS-ELECTROSPRAY MASS SPECTRA OF THE HERBICIDES PARAQUAT AND DIQUAT. Journal of the American Society for Mass Spectrometry 7(9):981-986, (1996).
Description:
The positive ion electrospray mass spectra of the quaternary ammonium salt herbicides paraquat and diquat are examined by on-line separation with capillary electrophoresis (CE) and by direct infusion of the analytes. The analytes are separated by CE in 7-10 min at pH 3.9 in 50% methanol-water by using several differenct separation buffer electrolytes. The capillary electrophoresis-eletrospray ionization (CE-ES) mass spectra of paraquat and diquat consist primarily of doubly charged molecular ions, singly charged molecular ions, and singly charged deprotonated ions. The direct infusion spectra consist primarily of doubly charged molecular ions and signly charged deprotonated ions. The relative abundances of the doubly charged and deprotonated ions depends strongly on the presence or absence of ammonium ion in the CE separation buffer or the direct infusion solution. A deprotonation mechanism is proposed in which the free base ammonia is the deprotonating agent in the desolvating charged dropkets or in the gas phase. The analytical potential of the CE-ES electrospray approach for environmental analyses is evaluated in terms of the precision of replicate injections, linear concentration range, and estimated detection limit.