Mass spectrometric determination of the special parameters of the potassium-calcium isotopic system

The K-40 similar to Ca-40 isotopic system is important to be used in the geochronology and trace geochemistry. The Ca-40/Ca-42 isotopic ratios and the Ca contents in the CaO reagent and Tahite standard have been determined by using the isotopic dilution mehtod and the Finnigan MAT-262 mass spectrometer. The Ca-40/Ca-42 ratios is 151.43 +/- 0.03 (n = 7) ( standard value: 151.47 +/- 0.03 (n = 5)), while the Ca-40 content in Tahiti is 2.036 +/- 0.003 mumol/g (n = 5) and its relative error between the measured and certified values is +/- 0.13%. The isotopic abundance of K-39, K-40 and K-41 in the national K standard is 0.93260 +/- 0.00012, 0.0001120 +/- 0.0000129 and 0.067286 +/- 0.000125, respectively. The K-39/K-41 ratio of the stable isotopes is 13.860 +/- 0.027 (n = 5), which is consistent to the value of 13.857 +/- 0.006 in the NIST-SRM985 international standard. the precise determination of the special parameters in the K-Ca system is the foundation of timing and tracing study in the future time.