An ICP-OES method for the precise and accurate quantification of rare earth elements in natural water: a comparative study from mine waste sites in New Mexico, USA

. In this work, we develop an analysis method using an Agilent 5900 ICP-OES instrument and report an assessment on the accuracy and precision for the quantification of REE in the natural waters collected from mine adits and an acid seep of mine sites in the Steeple Rock and Hillsboro mining districts, New Mexico, USA. The total REE concentrations in the water samples were measured using the methods we developed for both ICP-OES and ICP-MS. The power of the new ICP-OES method lies in routine analysis of µg/L level concentrations normally analyzed using ICP-MS, including a U.S. Geological Survey standard reference sample, laboratory blank samples spiked with a National Institute of Standards and Technology traceable standard, and surface water samples from mine waste sites. This ICP-OES method achieves low quantification limits ranging from 0.2 to 5 µg/L and excellent analytical accuracy and precision for REE analysis. The precision of light (La-Gd) and heavy (Tb- Lu) REE analysis using this method are better than 5% at average concentrations above 5 ± 4 µg/L and 3 ± 2 µg/L, respectively, and 3% at average concentrations above 10 ± 9 µg/L and 5 ± 4 µg/L, respectively. This method also shows excellent sensitivity and reproducibility for our laboratory and field samples.