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.