A new catalytic spectrophotometric method for determing trace arsenium has been proposed.The method is based on the catalytic effect of As(V) in discoloring reaction between KIO 3 and Thymol Blue in HCl medium (pH=0.8) and the presence of activator citric acid.The method has good selectivity and the linear range is 0.00～10.00μg/L,detection limit is 6.3×10 -11 g/ml.The method has been used for the determination of trace arsenium in celery,human hair and waste water samples,and RSD is 2.1%～3.2% and recovery is 97%～102%.
A new inhibition kinetic spectrophotometric medod for the determination of trace nitrobenzene was proposed,based on the inhibit effecy of initrobenzene on decoloration reaction of methyl orange (MO) for the oxidation of potassium iodate in the solution with pH=2.20 of hydrochloric acid and the activator stannous chloride.The kinetic condition of this reaction was investigated.Addition of the cetyl trimethyl aminonium bromide (CTMAB) can increase the sensitivity of the determination.The detection limit is 1.82×10 -7 g·L -1 ,ε 515 =1.2×10 5L·mol -1 ·cm -1 and the calibration graph is linear from 0.02～30.0μg·ml -1 nitrobenzene.The interference of aniline was eliminated by the addition of distillation in acidic solution.It was applied to the detemination of trace nitrobenzene in waste water with RSD=1.6%～2.3%.
