Capillary electrophoresis time-of-flight mass spectrometry of paraquat anddiquat herbicides

Capillary electrophoresis (CE) and mass spectrometry (MS) were investigated for the analysis of paraquat and diquat herbicides. The mass spectrometer was a home-built time-of-flight instrument (TOFMS) equipped with an electro spray ionization (ESI) source. A coaxial liquid sheath ESI source was utili zed for interfacing the CE to the TOFMS, and mass spectra were acquired wit h both liquid sheath and microspray sources. The ESI-TOF spectra of paraqua t and diquat were dependent on the background electrolyte composition; sing ly or doubly charged ions were displayed preferentially. Volatile buffer sy stems, compatible with the ESI-MS, were used in mixed aqueous/organic solve nts. By using the sample stacking technique at the CE injection port, low f emtomole detection was achieved from 5 mu M solutions. (C) 1999 John Wiley & Sons, Inc.