Sample oxidation procedures for the determination of chromium and nickel in biological material

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Abstract
Sample preparation methods for atomic absorption spectrophotometric analysis of chromium and nickel in biological materials were examined. Radiotracer recovery, precision of analysis and analysis of NBS reference samples were the criteria used. Chromium and nickel in biological materials can be successfully prepared for atomic absorption spectrophotometry by dry ashing with nitric acid treatment of the partially oxidized sample. It was necessary to use at least 5% nitric acid to extract the chromium and nickel from the ash. Wet digestion with nitric acid alone was satisfactory for nickel but not for chromium. Wet digestion gave greater variance and required considerably more time. We found no evidence of loss of chromium by either volatilization or insolubility. Since this method is satisfactory for nickel determination it may be implied that it is also satisfactory for other nonvolatile first transition series elements.