Determination of active chlorine in air by bonded phase sorbent collection and spectrophotometric analysis

Abstract

The development and application of a collection method for total combined gas-phase active chlorine (i.e., Cl₂, HOCl and chloramines) based on a sulfonamide-functionalized silica gel sorbent are presented. Preparation methods for the sorbent are described, as are procedures for chemical and physical characterization, such as chlorine capacity and chlorine collection efficiency. For determination of the collected chlorine, a modified version of the N,N′-diethyl-p-phenylenediamine (DPD) colorimetric method was employed, which yielded a detection limit of 0.1 µg of chlorine. At flow rates ranging from 31 to 294 ml min^–1, the collection efficiency was >90% based on breakthrough analysis. Recovery of chlorine spikes from 0.05 g aliquots of the sorbent was not quantitative (≡60%) but was reproducible; the recovery is accounted for in samples by adding weighed amounts of sorbent to the standards. Analytical data for active chlorine concentrations (i.e., Cl₂ + HOCl) above a swimming pool are presented.