SPECTROFLUORIMETRIC DETERMINATION OF DIQUAT BY MANUAL AND FLOW-INJECTION METHODS

A reliable, highly sensitive and selective method is described for the determination of the herbicide diquat in different materials. It involves the formation of a stable radical obtained by reduction of diquat with sodium dithionite. The radical is a very fluorescent species (phi-F = 0.37), and there is a linear relationship between diquat concentration and fluorescence intensity over the range 3-900-mu-g 1(-1). The limit of detection is 0.4-mu-g 1(-1). The method can be successfully adapted as a flow system using a two-channel manifold, the peak height being proportional to the diquat concentration over the range 18-4000-mu-g 1(-1). Manual and flow-injection methods were successfully applied to the determination of diquat in commercial herbicides, waters, potatoes, flowers and soils. Both procedures were also been applied to the determination of diquat in serum and urine without prior preparation of the samples and with good results.