A sensitive spectrophotometric method is proposed for the determination of trace amounts of hydrazine by a one-step condensation reaction with vanillin. The dye thus formed gives a yeflow colour in acidic medium, has a maximum absorbance at 400 nm and obeys Beer's law in the range 0.65-5 pg of hydrazine in 10 mi of the final solution. The optimum reaction conditions, such as time, temperature, pH, reagent concentration and effect of interferents, were determined for full colour development. The method has been applied successfully to the determination of hydrazine in polluted river water and in a biological fluid.

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A spectrophotometric method based on the indophenol reaction is described for the determination of phenol in water and biological fluids. Phenol reacts with ammonia and N-chlorosuccinimide in alkaline media with sodium nitroprusside as a catalyst to give a greenish blue indophenol dye. The dye has a maximum absorption at 670 nm. Beer's law is obeyed in the range 0.3-2.4 p.p.m. The molar absorptivity and the Sandell sensitivity are 3.30 x lo4 I mol-1 cm-1 and 0.0028 yg cm-2, respectively. The reaction conditions and other analytical parameters have been optimised. The method has been successfully applied to the determination of phenol in waste water and biological fluids.

A sensitive method is described for the spectrophotometric determination of acetone in water. Acetone reacts with vanillin in alkaline medium forming a yellow-orange dye with an absorption maximum at 430 nm. Beer's law is obeyed in the range from 0.5 to 5 p.p.m. of acetone in water. Molar absorptivity and Sandell's sensitivity were found to be 11.0 x 10(3) +/- 100 l mol-1 cm-1 and 0.005 micrograms cm-2, respectively. The important parameters for complete colour development were optimised and the method was used for the determination of acetone in biological samples. The method was also applied successfully to the determination of acetone in air after absorption in sodium hydrogen sulphite solution.