Determination of gallium in aluminium oxide by atomic absorption spectrometry with electrothermal atomisation: effect of gallium bond and aluminium oxide modification on the analytical signal under slurry atomisation conditions

Abstract

A method is reported for the determination of gallium in α-alumina powder (corundum) by electrothermal atomisation of the sample introduced in the form of a suspension (slurry) into a graphite atomiser, either on the wall or a platform [10 µl of 0.25% m/v suspension in ethanol-water (9 + 1)]. The measurements were carried out at 294.4 nm with deuterium background correction. For calibration, standard oxides were prepared either with gallium occluded within the alumina matrix or adsorbed on alumina present in the α-or γ-modification. It was found that alumina decreases markedly the volatility of gallium and increases the sensitivity of the determination in comparison with aqueous nitrate solutions containing no aluminium (ca. 8-fold when atomised from the wall for gallium occluded within α-alumina). The mini-platform effect of alumina on the atomiser wall is considered to be the main reason for the increase in peak size. When atomising from the platform, the peak of gallium occluded within α-alumina exhibits a time delay of about 500 ms compared with γ-alumina. Based on the ascertained dependences of the atomisation signal on several variables (including the mode of combining gallium with alumina, i.e., occlusion or adsorption), suitable procedures for correct calibration are suggested.