title: An improved candidate reference method for serum potassium measurement by inductively coupled plasma-mass spectrometry.
abstract: BACKGROUND
  In 2002, the National Institute of Standards and Technology (NIST) established a reference method for serum potassium based on inductively coupled plasma-mass spectrometry (ICP-MS). The aim of this study was to develop an inexpensive and improved candidate reference method for accurate and precise determination of serum potassium.
  
  
  METHODS
  Serum samples were diluted with 1% HNO3 supplemented with (59)Cobalt as isotope internal standard, and potassium was measured by ICP-MS. The new method was evaluated with NIST standard reference materials (SRMs), according to the Clinical and Laboratory Standard Institute's evaluation protocols.
  
  
  RESULTS
  At 4.300 and 4.678 mmol/l levels, the present method demonstrated analytical imprecision of 0.09% and 0.14%, and recoveries of 99.67% to 99.88%, respectively. The bias between the target values of SRMs were -0.02% to +0.28%, respectively. This method was linear between 0.0000 and 6.87 mmol/l (R(2)=1.000). The method had an uncertainty (U95%) of 0.76%.
  
  
  CONCLUSIONS
  The proposed ICP-MS method to measure serum potassium is precise and accurate, with high sensitivity and specificity. It may be considered as a candidate reference method for the determination of serum potassium.
authors.affiliation: Department of Laboratory Medicine, Beijing Chao-Yang Hospital, Capital Medical University, Beijing 100020, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Zhang
authors.forename: Huaian
authors.initials: H
authors.lastname: Ma
authors.forename: Huiling
authors.initials: H
authors.lastname: Li
authors.forename: Jing
authors.initials: J
authors.lastname: Xu
authors.forename: Jianping
authors.initials: J
authors.lastname: Zhang
authors.forename: Yang
authors.initials: Y
authors.lastname: Zhang
authors.forename: Qingtao
authors.initials: Q
authors.lastname: Wang
mesh_terms: D001774:Blood Chemical Analysis / Q000379:methods*; D006801:Humans; D013058:Mass Spectrometry / Q000592:standards; D011188:Potassium / Q000097:blood*; D012015:Reference Standards; D012680:Sensitivity and Specificity
chemical_list: D011188:Potassium