Determination of rare-earth elements in Arima spring water by ICP-MS with ion-exchange separation

ICP-MS was applied to the determination of rare-earth elements(REE) in Arima spring water. For the preconcentration of REE from matrix elements, an ion-exchange method using a chelating resin having an iminodiacetic acid functional group was applied. The analytical procedure was as follows: the dissolved iron in the sample, which forms hydroxide precipitates by pH adjustment and intefer the analysis of REE, was oxidized by HNO3 and then removed by an anion-exchange resin as a chloride complex under 4 M HCL acidity. The solution was adjusted to have a pH value of 5.5 with an acetate buffer and an ammonia solution, and was then stirred for 2 h after the addition of a chelating resin. The resin was collected by a glass filter and washed with a magnesium chloride solution, an ammonium acetate buffer solution and water to remove any alkali earth elements (Ca, Mg, Ba). REE adsorbed on the resin was eluted with 5 ml of 2 M HNO3. The Cd as an internal standard element was added to the eluent and diluted to 20 ml for determination by ICP-MS. The recovery of each REE was more than 90%. The total REE concentration and Eu anomalies of Na-Cl-Fe high-temperature spring water differed from Na-Cl-HCO3 low-temperature spring water in Arima.