Sensitive determination of nitrite by means of a Landolt-type reaction in fluorescent aggregates of a binaphthyl-based amphiphile

Abstract

The iodine quenching effect on the fluorescence of a binaphthyl-based amphiphile, C₈BNC₆N, was used for monitoring the Landolt-type reaction between nitrite, iodide, and thiosulfate. Due to the possibility of iodine detection in the 10⁻⁸–10⁻⁷ M range, and to the effective concentration of anionic reagents on the surface of cationic aggregates, the indicator reaction can be monitored using reagents at concentration levels as low as 10⁻⁷ M. To optimize the analytical system, the effect of pH and reagent concentrations on the rate of indicator reaction were studied. The influence of the matrix of water samples and effect of side-reactions increasing the value of a blank test were examined. A procedure for nitrite determination in water was developed, using the diazo reaction for selective nitrite removal to provide a reference solution, which avoided possible effects of the matrix components. The usefulness of this method was tested by determining trace amounts of nitrite in water samples. The procedure allows determination of nitrite down to 5 ng/ml (detection limit about 2ng/ml) with r.s.d. of 10% in the 20–250 ng/ml range.