RAPID PARTIAL DIGESTION OF BIOLOGICAL TISSUES WITH NITRIC-ACID FOR THE DETERMINATION OF TRACE-ELEMENTS BY ATOMIC SPECTROMETRY

Determination of Cu, Fe, Mn and Zn in fresh bovine liver and BCR bovin e liver and pig kidney reference materials, after digestion at 105-deg rees-C with nitric acid for various times, showed that the trace eleme nts were completely released after heating for only 20 min. Centrifuga tion of the sameples after digestion improved the separation from undi gested fat. This partial-digestion method, based on heating about 0.2 g of sample with 2 ml of nitric acid for 20 min, was tested on a range of biological reference materials and on fresh bovine liver for the f our elements. Comparison was made with results obtained after digestio n by a recommended hydrogen peroxide-sulfuric acid digestion procedure . Results obtained by inductively coupled plasma atomic emission spect rometry or by flame and graphite-furnace atomic absorption spectrometr y showed good agreement between the two digestion procedures, and resu lts for the reference materials agreed well with the certified values. Between-batch precision was better than 4% for Cu, Fe and Zn at level s of 30 to 190,210 to 320 and 100 to 140 mug g-1, respectively. For Mn , the precision varied between 7 and 14% for measured concentrations o f 8 to 12 mug g-1. The partial-digestion procedure offers simplicity, speed, low cost and the ability to handle a large number of samples at the same time.