Microfunnel magnetic stirring-assisted liquid–liquid microextraction method for determination of trace amounts of gold after optimization employing response surface methodology

Development of a dispersive liquid-liquid microextraction technique for ultra-sensitive detection of gold in environmental samples using atomic absorption spectrometry

The work examines the determination of gold from environmental samples by dispersive liquid-liquid microextraction (DLLME) method. The method was developed for the separation and determination of Au (III) ions after chelating with bis (salicylaldehyde) ethylenediimine (H2SA2en) Schiff-base as derivatizing reagent. Flame atomic absorption spectrometry (FAAS) and inductively coupled plasma-optical emission spectrometry (ICP-OES) techniques were used for quantitation of Au (III). These techniques are sensitive and rapid for the determination of gold concentrations in ore, water and sediment samples. The influence of factors such as pH, reagent concentration, solvents (extracting) (disperser) and solvent volumes on extraction efficiency of Au (III) ions were studied and optimized by univariate and multivariate techniques. The linearity of the method was in the range of 2 to 12 µg/L with R2 = 0.997. The limit of detection was 1 µg/L, and the limit of quantification was 3 µg/L. The preconcentration factor and enrichment factor values were 44 and 47. The repeatability (the intra-day) and reproducibility (the inter-day) precisions (n = 3) were found to be 0.417-3.56%. The proposed method was successfully applied for the determination of gold in sediment samples of the Indus River, Kori Barrage, goldsmith water, acidic solution of goldsmith and ornament samples collected from Goldsmith Labs and shops. The results found from FAAS were compared with those obtained from ICP-OES technique, and a good correlation with comparable selectivity and sensitivity was specified.

Development of a selective and sensitive colour reagent for gold and silver ions and its application to desktop scanner analysis

Desktop scanners can be favorable alternatives to sophisticated spectrophotometers for the assessment of analytes in complex real samples. Distinctively, our method has been thoroughly investigated, optimized, validated and successfully applied to the assessment of silver and gold in complex real samples, applying syringal rhodanine (SR) as a novel specifically tailored chromogenic reagent and using a desktop scanner as a versatile sensor. Maximum colour absorbance was obtained in the presence of cetylpyridinium chloride (CPC) and cetyltrimethylammonium chloride (CTAC) for silver and gold chelates, respectively. For each metal ion, two ternary complexes were formed depending on the SR concentration with stoichiometries of 1 : 1 : 1 and 1 : 2 : 3 (Ag-SR-CPC) and 1 : 2 : 3 and 1 : 3 : 4 (Au-SR-CTAC), respectively. The methods adhered to Beer's law for 0.15-2.5 and 0.15-2.25 μg mL-1 with detection limits of 0.0089 and 0.0163 μg mL-1 for silver and gold, respectively. The molar absorptivities were 3.63 × 104 and 6.15 × 104 L mol-1 cm-1 at 550 nm and 554 nm, with Sandell's sensitivity indexes of 0.0029 and 0.0032 μg cm-2, respectively. The method was successfully applied to the assessment of silver and gold in a wide range of complex environmental samples.