This document describes an analytical method for the electrochemical assay of pure plutonium nitrate solutions of nuclear grade@ with a total uncertainty not exceeding ??0@2 % at the confidence level of 0@95 for a single determination (coverage factor@ K = 2). 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 requires experimental demonstration by the user that applicable data quality objectives will be met. For some applications@ purification of test samples by anion exchange is required before measurement to remove interfering substances when present in significant amounts. Refer to Clause 10 for a discussion of interferences and corrective actions. Purification is also appropriate in situations where the purity of the test sample is unknown or when it may fluctuate unpredictably in a manufacturing process. Clause 11 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 document.