Flow-injection determination of elemental iodine by polyvinyl alcohol

Complex formation between elemental iodine and polyvinyl alcohol was studied under flow conditions. The formation of substances with a weak hyperchromic effect in the UV and visible regions was detected. It was shown that this reaction could be used under flow conditions provided the gel-forming ability and viscosity of the polyvinyl alcohol solution were reduced by adding isopropanol and 6% dimethylsulfoxide. It was found that the reaction efficiency under flow conditions could be monitored using a new method for the determination of the dispersion coefficient of a sample based on comparison between standard and “flow” absorptivity coefficients. Because of the effect of nonequilibrium factors, it turns out that the best calibration function is a nonlinear one. The throughput capacity of the method is 140 samples per hour, and the limit of detection is 60 ng/mL. The high selectivity for chlorides allows one to determine iodine and its species in seawater and to monitor its concentration in white salt.