Copper determination in biological materials by ETAAS using W–Rh permanent modifier

A tungsten–rhodium treatment on the integrated platform of a transversely heated graphite atomiser was used as a permanent chemical modifier for the determination of copper in biological materials by using digested samples as well as slurry sampling in electrothermal atomic absorption spectrometry. The W–Rh permanent modifier was as efficient as Pd+Mg(NO3)2 conventional modifier for obtaining good Cu thermal stabilisation in the digested and slurry samples. The permanent W–Rh modifier remained stable by approximately 300 and 250 firings when 20 μl of digested sample and 20 μl of slurry were delivered into the atomiser, respectively. In addition, the permanent modifier increased the tube lifetime up to 1370 and 744 analytical measurements in the digested and slurry samples, respectively. Also, when the W–Rh permanent modifier was employed, there was less variation of the slope of the analytical curves during the total atomiser lifetime, resulting in a decreased need of re-calibration during routine analysis, increasing the sample throughput, and consequently diminishing the variable analytical costs. Detection limits obtained with W–Rh permanent modifier were 0.64 and 0.33 μg g−1 Cu for digested (dilution factor 100 ml g−1) and 1.0% m/v slurries of biological materials, respectively. Results for the determination of copper in the samples were in agreement with those obtained with decomposed sample solutions by using Pd+Mg(NO3), since no statistical differences were found after applying the paired t-test at the 95% level.