Phase transfer catalyst assisted directly suspended droplet microextraction of platinum from geological and spent automobile converter samples prior to HR-CS AAS determination

Abstract

A rapid phase transfer catalyst assisted directly suspended droplet micro-extraction (PTC-DSDME) procedure was developed for the separation and pre-concentration of hydrophilic ionic platinum from the digested geological and spent automobile converters prior to its determination by high resolution continuum source atomic absorption spectrometry (HR-CS AAS). The method is based on the formation of extractable hydrophobic species of anionic platinum with quaternary ammonium solubilising sites of a phase transfer catalyst in a bulk aqueous phase, in the presence of an acid mixture. The formed hydrophobic species are separated from the bulk aqueous phase and pre-concentrated into a micro-volume of suspended 1-undecanol droplet, avoiding the addition of an external chelating agent. Several factors influencing the extraction efficiency, such as the nature and volume of organic solvent, stirring rate, different PTCs and extraction time were evaluated and optimized. The proposed method was applied to synthetic samples, spent catalytic converters and geological samples. The spiked recoveries were in the range of 99–102%. Under the optimized conditions, a detection limit of 0.28 ng mL⁻¹ and a good relative standard deviation of ±1.5% at 5.0 ng mL⁻¹ were obtained (n = 6). The accuracy of the procedure was evaluated by analyzing Canadian certified reference materials such as PTC-1a copper–nickel sulphide concentrate and PTM-1a copper–nickel sulphide matte samples. The results showed that PTC-DSDME combined with HR-CS AAS is a rapid, sensitive, and low-cost procedure requiring minimum organic solvent and an efficient analytical method for the separation and determination of trace amounts of platinum from various matrices.