Analytical Sciences

Abstract − Analytical Sciences, 16(7), 707 (2000).

Determination of Diquat and Paraquat in Water by Liquid Chromatography/Electrospray-Mass Spectrometry Using Volatile Ion-Pairing Reagents
Masahiko TAKINO,* Shigeki DAISHIMA,** and Kenji YAMAGUCHI**
*Kansai Branch Office, Yokogawa Analytical Systems Inc., 3-3-11 Kinryo Bld., Niitaka, Yodogawa, Osaka 532-0033, Japan
**Yokogawa Analytical Systems Inc., 2-11-13, Nakacho, Musashino, Tokyo 180-8453, Japan
A method for the determination of the herbicides paraquat and diquat in water was developed using liquid-chromatography/electrospray ionization-mass spectrometry (LC/ESI-MS). This method did not include any sample-concentration steps. Only 0.1 M nonafluoropentanoic acid (NFPA) was added to the filtered sample. An aliquot (200 muL) of this sample was analyzed by reversed-phase liquid chromatography with the postcolumn addition of 2-propanol followed by ESI-MS. Paraquat and diquat were detected using the [M2+ -H+] ion at m/z 185 and 183, respectively. Quantification was performed by an external standard method. The detection limits were 0.1 ng/mL (paraquat) and 0.2 ng/mL (diquat). The repeatability and reproducibility were 2.1% and 7.4% for paraquat and 2.7% and 8.1% for diquat.