Optimized conditions and analytical performance for the determination of Cu in serum and urine samples using a single GFAAS procedure

The determination of copper in biological samples is of major importance in clinical chemistry and very often, especially when Wilson's disease is sus pected, the simultaneous analysis of both serum and urine is necessary. The refore, a single analytical procedure with proven reliability in the simult aneous determination of copper in both matrices becomes of great practical interest for clinical laboratories. This work describes the optimization and evaluation of a Zeeman-effect back ground correction GFAAS method. It differs only in the prior dilution of th e serum samples (1+24) and allows the determination of copper in both serum and urine samples with proven accuracy, precision, and robustness. The method provides a limit of detection of 0.98 mug/L, a limit of quantifi cation of 3.3 mug/L, and a characteristic mass of about 23 pg. Repeatabilit y (%RSD) was 1.3% for a standard solution (20 mug/L), 2.4% for urine (26 mu g/L), and 1.4% for serum (29 mug/L) samples. Between-run and between-day re producibility was typically better than 5%. Accuracy has been assessed usin g the standard additions method/calibration curves slope ratio, which was 1 .057 for serum and 1.023 for urine, and by the analysis of commercial contr ol samples. Additional evaluation of the results obtained in the determinat ion of copper in serum was made by comparison with Flame AAS analysis.