US Patent 7226790 Method for measurement using sodium azide

A method of measuring an analyte in a sample with excellent sensitivity using a redox reaction is provided. In this method, a reducing substance or an oxidizing substance derived from the analyte is measured in the presence of a tetrazolium compound and sodium azide using the redox reaction, and an amount of the analyte is determined from the amount of the reducing substance or oxidizing substance thus measured. The tetrazolium compound and the sodium azide are present at a ratio in a range from 20:3 to 20:12. Preferably, a solution containing the tetrazolium compound and the sodium azide is aged and then added to the sample.