Method development for the determination of alkali metals in samples from pyrochemical reprocessing using ICP-OES and comparison with sector field ICP-MS

Abstract

An analytical procedure for the reliable determination of the alkaline elements Na, K, and Li in radioactive samples was developed and validated. To this end, a high efficiency, desolvating nebulizer (Apex E) was coupled to a commercial high resolution ICP-OES instrument operated at 1000W. Because of their radioactive nature, all investigated samples were handled in appropriate glove boxes operated in under-pressure, following strict safety and security procedures. After optimization of the ICP-OES operational parameters, detection limits (LODs) of 0.15μg/L, 0.8μg/L, and 1.3μg/L were obtained for Li (λ=670.784nm), Na (λ=589.592nm), and K (λ=766.490nm). Compared to conventional sample uptake rates of 1–2mL/min, the 350μL/min used in this study helped to lower the radiation dose to the ICP-OES operator and produced much less radioactive waste while at the same time improving LODs. Calibration curves were linear up to 4mg/L with a correlation coefficient of better than 0.999. Because of its robust and reproducible performance, no internal standard was required to correct for potential drifts in sensitivity of the ICP-OES. Three certified water reference materials (BCR®-617, LGC6177, SRM® 1643a) were employed to assess the accuracy of the developed ICP-OES procedure, the results of which underpin its reliability. In addition, Na and K concentrations calculated from emission intensities measured at two wavelengths confirmed that each dataset is consistent in itself. A comparison of sector field ICP-MS results of 23 samples originating from pyrochemical reprocessing with the data obtained applying the newly developed ICP-OES procedure revealed that the latter provides a reliable, straightforward and more robust analytical approach to determine Na, K, and Li in radioactive specimens.