Determination of ionic nickel and cobalt in simulated PWR coolant by differential-pulse polarography

Abstract

Differential-pulse polarography has been investigated for the simultaneous determination of soluble nickel and cobalt in simulated PWR coolant. This method used dimethylglyoxime enhancement of the peak current and as such has advantages over electrothermal atomic absorption in that there is no dispersion of the sample into the atmosphere, which is an important consideration when the samples are radioactive.

It was shown that the presence of boric acid in a sample, whose pH was buffered to pH 8.8 with ammonium tartrate, did not have any significant effect. The limit of detection for both metals was of the order of 0.3–0.4 µg l^–1. The relative standard deviation was found to be less than about 5% at 5 and 10 µg l^–1. A linear calibration graph was found for both metals over the range 0–20 µg l^–1. Other metal ions likely to be present as corrosion products in PWR coolant, such as chromium, manganese and iron, had no significant interference effects.

These performance statistics indicate that this technique would be suitable for the determination of nickel in PWR coolant where the expected concentrations lie in the approximate range 1–10 µg l^–1. The technique is not ideal, however, for the determination of cobalt as the expected concentrations are less than 1 µg l^–1.