Rapid and Accurate Determination of 226Ra from Drinking Water Using Macropa-Mediated Cloud Point Extraction Coupled with ICP-MS/MS.

A novel protocol has been developed for the preconcentration, separation, and accurate quantification of Radium-226 (226Ra) from drinking mineral water samples by cloud point extraction (CPE) coupled with inductively coupled plasma tandem mass spectrometry (ICP-MS/MS). To the best of our knowledge, this is the first report on using CPE to preconcentrate Ra. This method was extended to determine 226Ra concentration in mineral water samples collected from tap and bottled water. To preconcentrate 226Ra, CPE was performed using Macropa as a selective chelating agent and Triton X-114 as the nonionic surfactant. Factors influencing the extraction efficiency (namely pH, ligand concentration, surfactant concentration, and hydrophobizing and salting-out agents) were studied and optimized for quantitative extraction (>95%). Adding hydrophobizing agents, such as octylamine, cetylpyridinium chloride, and benzyltrimethylammonium chloride, significantly enhanced the capacity to extract Ra (>95%) via CPE. The optimized conditions were applied to preconcentrate 226Ra from 250 mL of water samples (tap and bottled), which were subsequently quantified by ICP-MS/MS. The limit of detection (LOD) of the method was 2 mBq L-1 (55 fg L-1), and the limit of quantification (LOQ) was 8 mBq L-1 (219 fg L-1), significantly lower than national and international drinking water guidelines.