Polyvinyl alcohol as a useful indicator on iodometry. (II): Temperature dependence of iodine recovery and the correction method of iodine concentration in the lower detection limit region.

In an iodometric titration method for iodine (or chlorine) analysis, the percent recovery of iodine (or chlorine) decreases in the low concentration region and at the relatively higher temperature range. We have shown that the percent recovery vs. concentration curve can be expressed by a simple empirical formula. The empirical formula contains parameters that depend on temperature and those parameters were obtained as a function of temperature. The empirical formula can be used as a correction function for experimental iodine (or chlorine) concentrations. By applying the correction function with the parameters to the experimentally obtained concentrations, we can estimate the reliable concentration in the low concentration region. Estimated concentrations were within 10% (as RSD) of the exact values after the correction in the range of 0.4 mg I2 L(-1) ([triple bond] ca. 0.1 mg as Cl2 L9-1)) - 4.4 mg I2 L(-1) ([triple bond] ca. 1.2 mg as Cl2 L(-1)) in the temperature range of 0 to 30 degrees C.