Determination of traces of nitrite and nitrate in water by solid phase spectrophotometry

A simple and sensitive method for the determination of nitrite and nitrate in water using solid phase spectrophotometry is described. The method utili zes the quantitative and rapid sorption of the dye formed from nitrite, usi ng the Griess reaction, into a thin layer of polyurethane foam (PUF) where a preconcentration factor of > 140 has been achieved. Nitrate is pre-reduce d using a cadmium reductor before applying the Griess reaction. The direct spectrophotometric measurement of the dye enriched in the solid foam phase has allowed the detection of as little as 5 and 40 ng ml(-1) nitrite and ni trate, respectively. Optimization of the parameters affecting the quantitat ive formation and sorption of the dye into PUF has been considered. Analysi s of natural water samples has been performed. (C) 2000 Elsevier Science B. V. All rights reserved.