Abstract:

Objective To develop the national standard materials of lithium,sodium,potassium,magnesium,calcium and chlorine in compound frozen human serum and evaluate their performance,and to promote the standardization of lithium,sodium,potassium,magnesium,calcium and chlorine assays. Methods Serum samples without hemolysis,lipemia and choleplania were collected. After multiple filtration sterilization,serum pools were packed in ampoules in 3 levels' candidates and stored in -70 ℃. Potassium ion is used as a characteristic parameter for homogeneity evaluation by single factor analysis of variance. Potassium,sodium and chlorine ions were used as the characteristic parameters for stability evaluation by linear regression analysis. The value was assigned by reference methods or validated methods,and the uncertainty was calculated. The commutability of fresh serum samples between reference methods/validated methods and 4 conventional analysis systems was evaluated. Results The F values of homogeneity for potassium ion in 3 levels' candidates were 1.630 1,1.498 6 and 1.020 8,respectively. All of them were <F_0.05. The stabilities of potassium, sodium and chlorine ions can be last at least 30 d at -20 ℃,2-8 ℃ and 20-25 ℃. The assigned values for lithium,sodium,potassium,magnesium,calcium and chlorine ions were：lithium 0.649±0.022,1.195±0.032 and （1.334±0.008） mmol/L;sodium 120.057±2.206,142.030±1.521 and （158.228±1.293） mmol/L;potassium 5.042±0.143,5.739±0.106 and （6.158±0.094） mmol/L;magnesium 0.732±0.021,0.857±0.026 and （1.144±0.026） mmol/L;calcium 2.014±0.078,2.348±0.056 and （3.070±0.024） mmol/L;chlorine 90.814±2.005,108.875±0.908 and （128.156±1.453） mmol/L（k=2）. The linearities for sodium,potassium,magnesium,calcium and chlorine ions were all within 95% confidence intervals,and the commutability was good. Conclusions The homogeneity and stability of candidates all meet the requirement,and their values are assigned accurately and reliably. The commutabilities of sodium,potassium,magnesium,calcium and chlorine ions in candidates are good. They can be used as national standard materials.

Key words: Lithium, Sodium, Potassium, Magnesium, Calcium, Chlorine, Frozen human serum, National standard material