DETERMINATION OF PARAQUAT BY FLOW-INJECTION SPECTROPHOTOMETRY

The solution obtained by oxidizing some of the ascorbic acid to dehydr oascorbic acid by reaction with potassium iodate is used as a reagent for the reduction of paraquat to a blue radical cation in the flow-inj ection spectrophotometric determination of paraquat. A rectilinear cal ibration graph was obtained over the range 0.1-100 mu g ml(-1) paraqua t, and the limit of detection was 20 ng ml(-1) paraquat (signal-to-noi se ratio = 3). This reagent has been found superior to ascorbic acid a lone or sodium dithionite because of the lower limit of detection, wid e linear range of determination, rapid reaction and high stability.