Thermal Lensing Colorimetry of Nitrite Ion with Single-Laser System

Abstract

Thermal lensing colorimetry has been applied to the determination of nitrite ion. Color development was based on the diazo-coupling reaction among NO2−, N-(naphthyl)-ethylenediamine dihydrochloride, and sulfanylamide. The source was the chopped output of an Ar+ laser operated at 514.5 nm. The beam intensity was measured with a silicon photocell of 1 mm2 surface area and the resultant electrical signal was processed with a microcomputer system. The minimal detectable amount of nitrite ion using a cell of 1 cm path length is 0.2 n M. This is more than 200 times smaller than the detection limit of ordinary spectrophotometry using a commercial spectrophotometer.