Ultratrace Elements in Terrestrial Water as Determined by High-Resolution ICP-MS

Abstract

The double-focusing inductively coupled plasma-mass spectrometry (ICP-MS) was proved to be an extraordinarily sensitive analytical technique. When this ICP-MS was combined with an ultrasonic nebulizer to increase the sample introduction efficiency, the detection power of the system was enhanced even further. The detection limits of most elements attained by this technique were less than 0.1 ppt and reached as low as 1 ppq (1/1000 ppt) for several elements. Analytical results of the standard reference materials, SRM 1643c (trace elements in water) provided by the National Institute of Standards and Technology, and SLRS-2 (riverine water) supplied by the National Research Council of Canada showed that the concentration values obtained by this method were in good agreement with the certified values for all the elements examined. Although the concentration levels of elements in freshwater were in most cases lower than 1 ppm with the exception of several major elements (Na, K, Ca, Mg, Si, S, and CI), it was possible to determine around 40 ultratrace elements (Li, Be, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Rb, Sr, Y, Cd, Cs, Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Th, Dy, Ho, Er, Tm, Yb, Lu, TI, Pb, Bi, Th, and U) with acceptable speed (less than 30 s per element) and precision (around 5% RSD) by direct sample introduction. No sample pretreatment, such as chemical separation and/or preconcentration, was necessary. It was also possible to directly determine as many as about 40 ultratrace elements in rainwater on as routine basis, although a much longer integration time (about 5 min/element) was applied because the concentration levels of elements in rainwater are far lower than those observed in river and lake water,