The determination of potassium in human serum by isotope dilution inductively coupled with plasma mass spectrometry

Objective To establish a method for the determination of serum potassium using isotope dilution inductively coupled plasma mass spectrometry. Methods Frozen human serum pools of different potassium concentrations were prepared from healthy donors of Chao-yang Hospital laboratory in 2010 Serum samples were diluted with 1% HNO3 supplemented with 41K spike and isotope ratio was measured after selection and optimization of ICP-MS analysis conditions.Serum 39K concentrations were calculated by interpolation method.3 different serum samples were used to evaluate the precision of the method.Standard Reference Material 909bⅠ and Ⅱ of National Institute of Standards and Technology were used to evaluate the accuracy.The recovery was evaluated through 2 serum samples added standard material for potassium,uncertainty was calculated. Results The analytical precision of serum potassium measurement was 0.14% to 0.11%.The results of SRM909bⅠandⅡgave the coefficients of variation (CVs) of 0.39% to 0.32%.Data was consistent with the certified value and the CV was +0.12% and +0.49% respectively.The recovery was 99.68% to 100.12% for 2 different serum samples. Conclusions ID-ICP-MS method was successfully established to measure the serum potassium concerntration precisely and accurately,it is an ideal method for the accurate determination of inorganic elements. (Chin J Lab Med,2013,36:828-831) Key words: Potassium; Isotope labeling; Mass spectrometry