Comparison of procedures for determination of copper and zinc in serum by atomic absorption spectroscopy.

Methods used to prepare serum samples for the determination of copper and zinc by atomic absorption spectroscopy have been compared using the results obtained from an external quality control scheme. The methods most commonly employed were dilution with water, dilution with dilute butan-1-ol or propan-1-ol, removal of protein by trichloroacetic acid (TCA) precipitation and electrothermal atomization (ETA). The effects of the inclusion of sodium and potassium ion upon results has been examined. Low results for serum copper are given by the technique of ETA. High zinc values are found following TCA precipitation. None of the methods showed superior between-batch precision. Ionization interference was variable and the addition of sodium and potassium to standard solutions is not always necessary.