A simple method of determination of nitrobenzene and nitrochlorobenzene in air and urine

An analytical method based on the direct coupling of the dye sodium salt of 1,2-naphthoquinone-4-sulphonic acid with the chemically converted nitrobenzene (NB) and p-nitrochlorobenzene (NCB) to aniline and p-chloroaniline in aqueous medium (pH 7.0-9.0) is presented. The coupled dye is extracted in carbon tetrachloride and spectrophotometrically determined at 450 nm wavelength. Carbon tetrachloride is found to be a selective solvent for extraction of aniline and its analogous coupled derivative of the dye, thus the interference of the other urinary nitro and amine compounds normally present is removed. Ethanol and isopropyl alcohol are efficient sampling media for trapping airborne NB and NCB vapors. The sensitivity and precision of the method are 10 micrograms and 3.5%, respectively, for NB and NCB in air samples. The sensitivity and precision of this method for urinary NB and NCB estimation is 0.8 mg/L and 0.6 mg/L; and 6.1% and 4.0%, respectively.