Catalytic determination of iodide by continuous addition of catalyst to a reference solution with photometric probe monitoring

Probe photometry is proposed as a simple monitoring technique for catalytic determinations by continuous addition of catalyst to a reference solution. The approach has been tested on the catalytic determination of iodide which in the concentration range of 10-100 ng/ml, can be determined with a relative error usually lower than 4-5% and relative standard deviations of 4.6 and 4.0% for 9.98 and 79.92 ng/ml, respectively. Two alternative techniques of measuring the analytical signal (the intersection time) are suggested to improve the reproducibility: the "initial signal preadjustment" and the "two-intersection point" techniques. The method has been applied to determination of iodide in table salt samples.