Routine analysis of ultra pure water by ICP-MS in the low- and sub-ng/L level

The chemical analysis with inductively coupled plasma-mass spectrometry (IC P-MS) can help to examine the purity of ultra pure water (UPW) down to 10 p art per trillion (ng/L) and lower. For a proper determination of a high num ber of samples per week the analysis must be divided into two parts: the ro utine analysis and the reference water analysis. The routine analysis is do ne by direct measurement of the ultra pure water samples. Applying a standa rd addition method under particular clean conditions, the reference water a nalysis leads to the definition of the accurate zero. A quick evaluation sc heme is also presented for the reference water analysis. The method is test ed for its fitness for application by examining LOD (for relevant element < 2 ng/L), reproducibility and linearity of calibration. The ICP-MS was opti mized according to the methodology of G. Taguchi to improve reproducibility and LOD.