Fast Detection of Lead Dioxide (PbO2) in Chlorinated Drinking Water by a Two-Stage Iodometric Method

Lead dioxide (PbO2) is an important corrosion product associated with lead contamination in drinking water. Quantification of PbO2 in water samples has been proven challenging due to the incomplete dissolution of PbO2 in sample preservation and digestion. In this study, we present a simple iodometric method for fast detection of PbO2 in chlorinated drinking water. PbO2 can oxidize iodide to form triiodide (I-3(-)), a yellow-colored anion that can be detected by the UV-vis spectrometry. Complete reduction of up to 20 mg/L PbO2 can be achieved within 10 min at pH 2.0 and KI = 4 g/L Free chlorine can oxidize iodide and cause interference. However, this interference can be accounted by a two-stage pH adjustment, allowing free chlorine to completely react with iodide at ambient pH followed by sample acidification to pH 2.0 to accelerate the iodide oxidation by PbO2. This method showed good recoveries of PbO2 (90-111%) in chlorinated water samples with a concentration ranging from 0.01 to 20 mg/L In chloraminated water, this method is limited due to incomplete quenching of monochloramine by iodide in neutral to slightly alkaline pH values. The interference of other particles that may be present in the distribution system was also investigated.