Chemiluminescence sensor with uranine immobilized on an anion-exchange resin for monitoring free chlorine in tap water

A chemiluminescence sensor using a xanthene dye immobilized on an ion-exchange resin as an indicator phase is described for the continuous monitoring of free chlorine (HOCl) in tap water. Of the dyes and ion-exchange resins tested, the immobilization giving the best dynamic response characteristics was achieved with a combination of uranine and a weakly basic anion-exchange resin (Amberlite IRA-93). The sensor, a Pyrex tube (20 mm × 3 mm i.d.) packed with the resin and placed close to a photomultiplier tube, provided a constant signal within ca. 1 min of a concentration change of free chlorine, a linear calibration graph between 1 × 10^?3 and 2 × 10^?6 M (the detection limit at a signal-to-noise ratio of 3) and an r.s.d. of 1.6% for 1 × 10^?5 M free chlorine. The sensor was unique in being insensitive to chloramines and permitted free chlorine to be determined in tap water with no interference from chloramines and other compounds.