Direct determination of zinc in whole blood, plasma and urine by atomic absorption spectroscopy

Abstract

Methods are described for the determination of zinc in plasma diluted twenty-fold with 0.1 N HCl, in whole blood diluted one hundred times and urine diluted tenfold, using a Perkin-Elmer 303 atomic absorption spectrophotometer. An analytical rate of 10 samples per hour can be achieved. Suppression of up to 15% of the apparent zinc content by inorganic components of the sample was overcome by the addition of the appropriate amounts of those ions to the standard zinc solutions used in the determination. The organic components of the samples had no significant effect on the apparent zinc content. Random contamination presents a problem which was best detected by replicate analysis. Studies of the plasma zinc level of 20 normal subjects (10 men, 10 women) showed a significant difference ( p < 0.001) between samples taken fasting at 9.00 h and five hours later (14.00 h) after the usual meals. The mean values were: 9.00 h, men: 98 μg/100 ml, women: 96 μg/100 ml; 14.00 h, men: 80 μg/100 ml, women: 83 μg/100 ml. The difference in whole blood values taken fasting at 9.00 h and five hours later was not significant ( p > 0.6) and the means of the two samples were: men 584 μg/100 ml (range 414–794 μg/100 ml), women 582 μg/100 ml (range 342–700 μg/100 ml). The 24-h urine excretions were men 585 μg (range 263–817 μg) and women 414 μg (range 276–702 μg). This difference was significant ( p < 0.05).