A simple and sensitive method for the determination of nitrite and nitrate in water using solid phase spectrophotometry is
described. The method utilizes the quantitative and rapid sorption of the dye formed from nitrite, using the Griess reaction, into
a thin layer of polyurethane foam (PUF) where a preconcentration factor of >140 has been achieved. Nitrate is pre-reduced
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 nitrate, respectively. Optimization
of the parameters affecting the quantitative formation and sorption of the dye into PUF has been considered. Analysis of
natural water samples has been performed. © 2000 Elsevier Science B.V. All rights reserved.