We introduce a novel approach in simple and highly sensitive fluorometric determination of ammonium nitrogen. The proposed method is based on a fluorescence derivatization with benzyl chloride. The benzyl chloride was converted to a new fluorescent derivative by reaction with ammonium ion (NH4+) in the presence of sodium bicarbonate. The excitation and emission wavelengths were 258 and 284 nm, respectively. The effects of benzyl chloride concentration, sodium bicarbonate concentration, reaction temperature and time, and hydrochloric acid concentration were studied in detail. Under the optimal conditions of the experiment, the linear range for determination of ammonium nitrogen was 0.01-0.60 mg L-1, and the detection limit was 0.008 mg L-1. Relative standard deviation of eleven measurements for 0.40 mg L-1 NH4+-N was 2.6%. The method was successfully applied to the determination of ammonium nitrogen concentration in different water samples. The mechanism of the derivatization was further confirmed by Fourier transform infrared (FTIR) spectra.
Keywords:
ammonium nitrogen; fluorometric determination; derivatization; benzyl chloride
