Simultaneous dtermination of gold (III) and platinum (IV) by graphite furnace atomic absorption spectrometry after ion-pair extraction with Zephiramine

Abstract

A solvent extraction of gold and platinum was investigated by Zephiramine (tetradecyldimethylbenzylammonium)-iodoaurate(III) or iodoplatinate(IV)-chloroform systems, which was for a pretreatment in the simultaneous atomic absorption spectrometric determination of gold and platinum. A 2-channel atomic absorption spectrometer equipped with a graphite furnace atomizer unit was utilized. When the volume ratio of the aqueous/organic phase was 15 ml/2 ml, gold(III) and platinum(IV) were coextracted quantitatively into chloroform over the tested range of 4 M HCl to pH 11, provided that the concentrations of Zephiramine and potassium iodide in the aqueous phase were kept at more than 5 × 10−4 M and 6 × 10−2 M, respectively. Atomic absorption was measured as follows: the organic extract (20 µl) was injected into a graphite furnace and then dried (200°C-30 s), ashed (1000°C-60s) and atomized (2950°C-10 s) with an argon flow rate of 3.5 l/min. The linearities of the absorbance vs. the concentration in the aqueous phase were confirmed up to 67 ng/ml for gold (242.8 nm) and 1.3 µg/ml for platinum (265.95 nm). The sensitivities for 1% absorption were estimated to be 0.21 ng Au/ml and 7.9 ng Pt/ml. The standard deviations in 10 measurements were 2.3% for 16.7 ng Au/ml and 2.4% for 0.67 µgPt/ml. Numerous cations and anions gave no interfering effect even when present in 1000-fold amounts (by weight) over gold (III) and platinum (IV). The interference of copper(II) with gold(III) determination could be masked by adding 1,10-phenanthroline into the aqueous phase. As to platinum (IV), several ions such as chromium(VI), manganese (VII), iodate and periodate interfered with the determination. However, the addition of hydroxylammonium into the aqueous phase served to remove their interferences. This method was applied to the analysis of silver base alloys. © 1986, The Japan Society for Analytical Chemistry. All rights reserved.