Determination of trace levels of gold in water samples by flame atomic absorption spectrometry after preconcentration with dispersive liquid- liquid microextraction

Gold is one of the precious metals and extensively used in various areas. It is a nonessential element, and some reports about allergic eczematous dermatitis as well as some nephrotoxic effects have been published [1]. It may be also very toxic for human, animal organism, plants and accounts as a pollutant [2], because of its inhibiting effect upon the activity of many enzymes and its preventing effect upon DNA separation [3].Direct determination of trace amounts of gold in environmental, geological and metallurgical samples by flame atomic absorption spectrometry (FAAS) is difficult because of low sensitivity and matrix effects. Therefore, an initial sample pretreatment, such as preconcentration of the analyte and matrix separation, is often necessary for sensitive and interference-free gold determination [4].Several methods have been reported for the separation and preconcentration of gold. In this study, dispersive liquid-liquid microextraction (DLLME) was used as a novel microextraction technique for the separation and preconcentration of Au(I) ions which is based on a ternary component solvent system. 1-phenyl-1,2-propanedione-2-oximethiosemicarbazone (PPDOT) was used as the complexing reagent. The influence factors relevant to DLLME, such as pH, type and volume of buffer, type and volume ratio of extraction and disperser solvents were investigated and optimized. The detection limit was 0.65 ng.mL-1 with a preconcentration factor of 48, and the relative standard deviation (RSD) was 2.1 % (n=6, at 0.05 µg.mL-1). The method was successfully applied to the determination of trace amounts of gold in various water samples.