Automated separation and measurement of 226Ra and trace metals in freshwater, seawater and fracking water by online ion exchange chromatography coupled with ICP-MS

Abstract

An online solid-phase extraction method combined with ICP-MS was developed to separate and quantify low levels of 226Ra and other metals in drinking water, lake, river and sea water, and fracking fluids. A dual-column lab-on-valve and multi-syringe flow injection analysis (LOV-MSFIA) system was developed to provide precise measurement of 226Ra in samples with total dissolved solids (TDS) less than 2%. For samples with higher levels of TDS (up to 20%), a triple-column LOV-MSFIA system was developed, which used AG 50 W-X8 cation exchange, Sr spec andNobias Chelate resins. Compared to earlier automated systems for Ra analysis, the dual and triple column systems described here were optimized to accommodate smaller sample volumes, more precise flow control and lower limits of detection (LOD). The LOV-MSFIA system coupled with ICP-MS is a significant improvement over traditional methods for low level 226Ra measurements, which require extended sample holding and/or analysis time. External calibration and standard addition were used to quantify the concentration of Ra for the LOV-MSFIA system. After method optimization, LODs for 226Ra as low as 4.3 mBq L−1 (1.75 fg L−1) were obtained in different sample matrices. The concentrations of selected metals were also measured on the triple-column system, together with Ra, with a total online processing time of 28.5 min per sample. Thus, the online LOV-MSFIA system is shown to be a powerful tool for the rapid analysis of low levels of 226Ra, as well as other metals, in various types of aqueous samples.