Conclusions
Polar paraquat anddiquat can’t be separatedonaC8HPLC column
without adding ionpairmodifier to themobilephase. USEPAMethod
549.2 sometimes does not provideoptimum resolutionbut does allow
detection to0.14ngon column. Toovercome these limitations, wehave
developedamobilephasemodifier for rapid (11minutes), complete
(R>4.0) resolutionof paraquat anddiquat, withdetection to0.12ngon
columnwitha linearity rangeof 6.4ppb to100,000ppb for sample
analysiswithina single system.
Inaddition, the samplepreparationmethodpresentedhere, using solid
phaseextraction, resulted ina twohundred foldanalyte concentration,
withaccurate (greater than97%), reproducible (%RSD<6) recoveries
fromone liter water samples. TheSPE tube is aweak cationexchanger
optimized for this extractionmethod. This new simpleHPLCmobile
phaseandSPE samplepreparationeliminate complicatedanalytical
systems and improveoverall methoddetection limits.
