Simultaneous analysis of multi-elements in environmental waters with inductively coupled plasma mass spectrometry

ICP-MS is expected to be an effective tool to determine a causative element of health related crisis. In this paper, we have described the results of our preliminary studies in order to obtain a technical skill of simultaneous analysis of multi-elements using ICP-MS. We had chosen 36 elements as the objects of measurement and have discussed the fundamental subjects for the analyses using ICP-MS. We performed measurements of the 36 elements in environmental waters such as waters for drinking, river waters, and hot spring waters. Calibration curves for the majority of the elements came out to be linear over 4 orders of range, but those for Ag and Hg tended to lack linearity. These two elements (Ag and Hg) had been shown had decrease their activities in standard solutions with the elapse of time after preparation. Our experiments revealed that the quantification limits for the majority of the elements were satisfactory enough with lower than 0.2 ppb, although, those for B, Na, Si, K, Ca, Fe, and for Se were higher than 1 ppb, and 0.5 ppb, respectively. For the quantification of Hg, ICP-MS turned out to be inferior to reduced vapor-atomic absorption spectrometry (RV-AAS) because the lower quantification limit was 0.1 ppb with ICP-MS and 0.02 ppb with RV-AAS. It should be noted that Na, Mg, K, Ca, have substantial memory effects in addition to B, Hg which are well known to have the memory effect. We used a direct injection method to inject a sample into ICP-MS, because the flow injection method in order to diminish the memory effects according to the recommendation of the manufacture's was effective only for Hg analysis but not effective for B, Na, Mg, K, and Ca analyses. Using the conditions we had established in our preliminary study, we performed simultaneous analysis of the elements in commercially available mixed standard solutions. Our measurements revealed that the quantities measured were almost in good agreements with their standard values except Ca, Ag, Hg, Ag and Hg were owing to their characteristic in standard solutions, and Ca analysis were interfered with molecular ions of coexisting elements in the same solution. We also performed the analysis of the elements in environmental waters with standard additions. All the elements except Na, Mg, Si, K, Ca, Ag, Hg, and Be, Se were quantified with satisfactory recoveries from samples with Na concentrations, as one of the main components in waters, less than about 10 ppm. When the samples contained Na about more than 100 ppm, the recoveries of Ag, Hg, Se and all the elements with mass number (m/z) less than 70 were not good enough for reliable analyses. Accordingly, dilution of such samples were assumed to be effective for the reliable analyses. Through our experimental simultaneous multi-elements analyses of reservoir waters and tap waters using ICP-MS, we could obtain the information regarding to the changes in quantities and the pattern of elements in environmental waters and tap waters before and after the water purification. In conclusion, our study revealed that ICP-MS was an effective tool for simultaneous analysis of multi-elements in environmental waters. We have succeeded to establish the technical details for the analysis of multi-elements in environmental waters using only filtration and dilution of the samples.