This International Standard specifies an analytical method for the electrochemical assay of pure plutonium nitrate solutions of nuclear grade, with a total uncertainty of 0,1 % to 0,2 % at the confidence level of 0,95 for a single determination. The method is suitable for aqueous solutions containing more than 0,5 g/L plutonium and test samples containing between 4 mg and 15 mg of plutonium. Application of this technique to solutions containing less than 0,5 g/L, and test samples containing less than 4 mg of plutonium, must be demonstrated by the user as having adequate reliability for their specific application. Preliminary purification by anion exchange is required to remove interfering substances when present in significant amounts. Purification is also appropriate in situations where the purity of the sample is unknown or when it may unpredictably fluctuate in the manufacturing process. Refer to Clause 9 for a discussion of interferences and iron corrections. Clause 10 discusses the changes in application of the method and methodology that can be applied and important considerations when selecting measurement parameters, while still remaining within the intended scope of this International Standard.