title: A candidate reference method for serum calcium measurement by inductively coupled plasma mass spectrometry.
abstract: BACKGROUND
  Calcium is an important serum ion which is frequently assayed in clinical laboratories. Since quality assurance requires reference methods, the establishment of a candidate reference method for serum calcium measurement is important.
  
  
  METHODS
  An inductively coupled plasma mass spectrometry (ICP-MS) method was developed. Serum samples were spiked gravimetrically with aluminum internal standard, digested with 69% ultrapure nitric acid and diluted to test concentration. Then the (44)Ca/(27)Al ratios were measured by ICP-MS in hydrogen mode. The method was calibrated using 5% nitric acid matrix calibrators and the calibration function was established with bracketing method.
  
  
  RESULTS
  The correlation coefficients between the measured (44)Ca/(27)Al ratios and the analyte concentrations ratios were all >0.9999. The coefficients of variation of the measurements were 0.27% and 0.16% for two spiked serum. The analytical recovery was 100.24%. The accuracy of the measurement was also verified through measurement of certified reference materials. Comparison with recognized reference method and international inter-laboratory comparisons gave satisfied results.
  
  
  CONCLUSIONS
  New ICP-MS method is specific, precise, simple, and low in cost, and may be used as a candidate reference method in the standardization of serum calcium measurement.
authors.affiliation: Beijing Hospital, National Center for Clinical Laboratories and Beijing Engineering Research Center of Laboratory Medicine, Beijing, P.R. China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Yan
authors.affiliation: Beijing Hospital, National Center for Clinical Laboratories and Beijing Engineering Research Center of Laboratory Medicine, Beijing, P.R. China.
authors.forename: Menglei
authors.initials: M
authors.lastname: Ge
authors.affiliation: Beijing Hospital, National Center for Clinical Laboratories and Beijing Engineering Research Center of Laboratory Medicine, Beijing, P.R. China.
authors.forename: Rong
authors.initials: R
authors.lastname: Ma
authors.affiliation: Beijing Hospital, National Center for Clinical Laboratories and Beijing Engineering Research Center of Laboratory Medicine, Beijing, P.R. China.
authors.forename: Haijian
authors.initials: H
authors.lastname: Zhao
authors.affiliation: Beijing Hospital, National Center for Clinical Laboratories and Beijing Engineering Research Center of Laboratory Medicine, Beijing, P.R. China.
authors.forename: Donghuan
authors.initials: D
authors.lastname: Wang
authors.affiliation: Beijing Hospital, National Center for Clinical Laboratories and Beijing Engineering Research Center of Laboratory Medicine, Beijing, P.R. China.
authors.forename: Cuihua
authors.initials: C
authors.lastname: Hu
authors.affiliation: Beijing Hospital, National Center for Clinical Laboratories and Beijing Engineering Research Center of Laboratory Medicine, Beijing, P.R. China.
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.affiliation: Beijing Hospital, National Center for Clinical Laboratories and Beijing Engineering Research Center of Laboratory Medicine, Beijing, P.R. China.
authors.forename: Wenxiang
authors.initials: W
authors.lastname: Chen
authors.affiliation: Beijing Hospital, National Center for Clinical Laboratories and Beijing Engineering Research Center of Laboratory Medicine, Beijing, P.R. China. Electronic address: cbzhang@nccl.org.cn.
authors.forename: Chuanbao
authors.initials: C
authors.lastname: Zhang
mesh_terms: D002118:Calcium / Q000097:blood*; D006801:Humans; D013058:Mass Spectrometry / Q000592:standards*; D012015:Reference Standards
chemical_list: D002118:Calcium
keywords: Aluminum; Calcium; Inductively coupled plasma mass spectrometry (ICP-MS); Reference method; Serum