Ultra-sensitive quantification of sub-nanomolar levels of iodine in blood serum samples by kinetic-spectrophotometric method.

A simple and sensitive kinetic-spectrophotometric method is developed for the determination of trace amounts of iodine in blood serum samples based on its catalytic effect on the oxidation of Nile Blue A by potassium bromate in sulfuric acid medium and at 25°C. The absorbance is measured at 595.5 nm with the fixed-time method. The optimization of the operating conditions regarding concentration of the reagents, temperature, and interferences are also investigated. The calibration curve is linear over the concentration range between 20.0 to 500.0 ng ml(-1) of iodine with good precision and accuracy. The detection limit of the method is down to 12.0 ng ml(-1). The relative standard deviation for a standard solution of 100.0 ng ml(-1) of iodine is 1.32% (n = 10). The proposed method provides a highly sensitive, selective, and relatively rapid assay for iodine at ultra trace level without any pre-concentration and separation step. The method was applied to the determination of iodine in blood serum samples. The analytical results of the real samples were in excellent agreement with standard method.