Effect of the matrix of the standard on results of atomic absorption spectrophotometry of zinc in serum.

Zinc in pooled human serum, diluted 10-fold with demineralized water, was determined by flame atomic absorption spectrophotometry. Recoveries of zinc added to the serum were calculated by use of standards prepared in water, physiological saline, synthetic serum, or dilute HNO3 (10 ml/liter). The flow rates were essentially the same (9.1 to 9.3 ml/min) for water, diluted synthetic serum or actual human serum, and diluted nitric acid. The mean apparent percentage recoveries (plus or minus SD) were the best (102.6 plus or minus 2.5) when the standards were prepared in nitric acid; the values obtained when standards in water were used were too high (111.5 plus or minus 3.9); those with standards prepared in physiological saline (92.0 plus or minus 3.2) or synthetic serum (92.3 plus or minus 2.5) were too low.