Direct determination of selenium at the pg/g levels in polar snow and ice samples

Abstract

Selenium (Se) is an essential element for health of human and animal, but Se in excess is toxic. Studies of the occurrence of Se in successively dated polar snow and ice are of great interest, because the data can allow us to decipher the large-scale changes in the atmospheric Se cycle. However, the measurement of Se in polar snow and ice remains still a great challenge, because of the extremely low concentrations down to the low picogram per gram (10-12g/g) level. In addition, various interferences make the analysis more difficult. We present here the first results of the direct determination of Se in Greenland snow samples using ICP-SF-MS with Apex-ACM sample introduction system. The use of Apex-ACM sample introduction system was observed to effectively reduce spectral interferences in the Se measurement. The detection limit of Se was 6.9 pg/g, which is 10 times lower than that of commercial ICP-MS. The Se concentration of NIST SRM 1643e diluted to the concentration level in Greenland snow samples was repeatedly measured in order to evaluate the precision and accuracy of the Se data. The measured Se concentration (11.17±1.01 ng/g) showed very good agreement with the certified value (11.68±0.13 ng/g).