Solid sampling-graphite furnace atomic absorption spectrometry for the direct determination of Au in samples of various natures

Abstract

In this work, the possibilities of graphite furnace atomic absorption spectrometry for the direct determination of Au in solid samples (NIST SRM 2709 San Joaquin soil, CANMET PTC-1a Co–Ni sulfide concentrate and a vitamin complex) have been evaluated. The diverse volatilities of the matrixes resulted in different degrees of difficulty for Au determination. In this regard, the analysis of the less volatile samples (CANMET PTC-1a and NIST SRM 2709) was particularly challenging. For these materials, the addition of Na₂CO₃ solutions, in order to carry out a microfusion directly in the graphite furnace, was found to be essential to liberate structurally bound gold at a moderate temperature (2000–2100 °C). In all the cases investigated, accurate results were obtained by means of external calibration using aqueous standards. Every determination required ≈15–20 minutes. Precision ranged between 12 and 14% relative standard deviation. A detection limit of 15 ng g⁻¹ was calculated.