MICROWAVE METHOD FOR PREPARING ERYTHROCYTES FOR MEASUREMENT OF ZINC CONCENTRATION AND ZINC STABLE-ISOTOPE ENRICHMENT

A microwave digestion method to prepare human erythrocytes for measure ment of Zn concentration by atomic absorption spectrophotometry and st able isotope enrichment by mass spectrometry is described. Also descri bed is a process for purifying digested erythrocyte samples enriched w ith Zn stable isotope for analysis by fast atom bombardment mass spect rometry, Microwave digestion was investigated as a way to increase sam ple throughput by replacing a more time-consuming conventional oven as hing/hot plate wet digestion method. Pooled red blood cells and NIST b ovine liver standard reference material were digested by the two diffe rent methods and zinc recoveries compared by atomic absorption spectro photometry, Microwave and conventional methods yielded 11.7 +/- 0.1 an d 11.7 +/- 0.2 mu g/g (wet wt), respectively, for the pooled erythrocy tes, and Zn recovery from NIST bovine liver standard (certified 123 +/ - 8 mu g/g) was 128.2 +/- 1.2 and 127.4 +/- 1.3 mu g/g, p greater than or equal to 0.282, respectively. Microwave digestion improved the pro cessing of erythrocytes for atomic absorption spectrophotometry and ma ss spectrometry by reducing digestion time from 1 week to 2 h. In addi tion, a procedure for purifying digested erythrocyte samples by ether extraction and ion-exchange chromatography in preparation for mass spe ctrometry analysis of Zn stable isotope enrichment is outlined.