Viscosity adaption for an automated micromethod of flame atomic absorption spectrometry, and intracellular trace-element analysis after pressure decomposition: zinc determination in plasma and erythrocytes.

We measured zinc in the plasma of 50 normal persons, and in erythrocytes of six, by an automated micromethod of atomic absorption spectrometry. Using a rotation viscometer, we measured the viscosity and flow behavior of plasma, undiluted and equi-volume diluted (with water), from 12 patients, and, for comparison, of two- to 20-fold dilutions of an 870 mL/L glycerol solution. Erythrocytes were washed three times, lyophilized, and wet-ashed in a pressure decomposition device. The mean viscosity of equi-volume diluted plasma is about the same as that of the glycerol solution diluted 7.5-fold. The observed concentration of zinc in normal plasma was 13.8 (SD 1.9) mumol/L, with intra-assay CV (n = 30) of 2%, day-to-day CV (n = 22) 3.8%, and accuracy (measurement of an aqueous std.) 2.5%. The mean normal value for erythrocyte zinc was 34.7 micrograms/g, with intra-assay CV (n = 8) 5%, day-to-day CV (n = 6) 5.9%, and accuracy 4.6%. Our results compare well with those by neutron activation analysis, the differences in values being 3% for plasma, 1% for erythrocytes.