The reaction between paraquat, ascorbic acid, and Cresyl Violet in alkaline medium and in the presence of sodium dodecyl sulfate has been applied for the first time to the development of a kinetic-fluorometric method for the determination of paraquat. The reaction rate of this system is measured by using the stopped-flow mixing technique, which makes the method applicable to automatic routine analysis. Analytical data are obtained in approximately 30 s. The calibration graph is linear over the range 6-500 ng mL(-)(1), and the detection limit is 1.8 ng mL(-)(1). The relative standard deviation is <3%. The use of dynamic measurements at long wavelength favors the high selectivity of the method. Diquat behaves in this system similarly to paraquat, but its interferent effect is easily avoided by using cysteine. The proposed method has been applied to the determination of paraquat in tap water, milk, and white wine samples with recoveries of 89-104%.

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A simple and fast kinetic method for the determination of pindone in baits was developed. It is based on the inhibitory effect of this indanedione rodenticide on the luminescence of the europium(III)-thenoyltrifluoracetone system in the presence of cetyltrimethylammonium bromide. The relatively long lifetime of this system allows the time-resolved mode to be used, which eliminates any fluorescence signal. To avoid the potential static background signal of the sample, the difference between the initial rate obtained in the absence and presence of pindone is used as the analytical parameter, which is obtained within only 0.2 s with the aid of a stopped-flow mixing technique. The calibration graph is linear in the range 0.1-10.0 )•

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