Studying the capabilities of graphite furnace atomic absorption spectrometry for the discrimination of ionic copper from copper and/or copper oxide nanoparticles

This work explores the applicability of Graphite Furnace Atomic Absorption Spectrometry (GFAAS) for the discrimination of ionic copper (Cu 2+ ) from copper and/or copper(II) oxide nanoparticles (Cu NPs and/or CuO NPs). To perform the measurements of the NPs by GFAAS, the preparation of stable suspensions from commercial solid standards of NPs with different average sizes was first evaluated. Among the evaluated dispersion media, sodium dodecyl sulfate (SDS) provided the most stable suspensions for both Cu and CuO NPs. The atomization delay (t ad ), defined as the time to reach maximum absorbance, was used as the parameter to discriminate between Cu species. Under the evaluated conditions, Cu 2+ exhibited higher t ad values than the nanoparticulate forms. The t ad values remained constant for Cu concentrations ranging from 5 to 40 μg L -1 for all species, demonstrating the independence of the discrimination parameter from analyte content. In addition, similar concentration calibration slopes were obtained for all species, indicating the feasibility of performing the quantification using only Cu 2+ standards. The effects of pyrolysis and atomization temperatures, as well as the atomization heating ramp, on the resolution between the t ad values of the Cu species were evaluated. The best time resolution for the discrimination was obtained using a pyrolysis temperature of 350 °C, a very slow atomization heating rate of 100 °C s -1 and an atomization temperature of 2300 °C. Finally, the analysis of Cu 2+ and Cu NP mixtures revealed non-additive signal profiles, suggesting possible ion - NP interactions that modify the species distribution during atomization.