Indirect Spectrophotometric Determination of Microamount of Chlorine in Air

Chlorine in air was absorbed with NaOH solution to form NaClO, which was reacted with HCl to release free chlorine. Iodide was quantitatively oxidized to I2 by Cl2 and reacted with starch to give a blue colored product, with absorption maximum at the wavelength of 570 nm. Linear relationship between values of ΔA and mass concentration of chlorine was kept in the range within 1.0 mg·L-1, with detection limit (3s/k) of 5×10-5mg·L-1. The proposed method was applied to the analysis of samples of simulated gas and air nearby the factory. Values of recovery found by standard addition method were in the ranges of 101%-103% with RSD′s less than 2%.