Determination of serum urea by isotope dilution gas chromatography mass spectrometry:a candidate reference method / 中华检验医学杂志

ABSTRACT

Objective To develop a candidate reference method for the measurement of urea in human serum based on isotope dilution/gas chromatography/mass spectrometry.Methods [13C,15N2]Urea used as internal standard Was added to the serum sample and equilibrated with endogenous nonlabeled urea.The serum samples were treated with anhydrous ethanol to emove proteins by precipitation.The serum urea and labeled urea were converted into a trimethylsilyl derivative of 2-hydroxypyrimidine and analyzed by gas chromatography/mass spectrometry system with selected ion monitoring.The concentration of serum ureaWas calculated by the theory of bracketing method.Results The average value of within-run oefficient of vailation(CV),between-run CV and total CV of the procedure were 0.38%(ranged from 0.12%to 0.47%),O.62%(ranged form 0.49% to 0.87%)and 0.73%(ranged from 0.51% to 0.93%).Respectively.The analytical recoveries ranged from 99.37% to 100.95%.The resuhs of analyzing the certified refefence material SRM909b(Level Ⅰand Ⅱ)showed a bias less than 0.2%.Conclusion The procedure for measuring urea in serum is a highly accurate and precise method and can be used as a candidate reference method for serum urea assays.