Separation and enrichment of gold(III) from environmental samples prior to its flame atomic absorption spectrometric determination

Real time optical detection of gold in living cells through genetically-encoded probe

To study the efflux of gold (Au) in living cells, a genetically encoded fluorescence resonance energy transfer (FRET)-based sensor has been developed. The gold-sensing domain GolB from Salmonella typhimurium has been fused to the N- and C-termini of the FRET pair enhanced cyan fluorescent protein (ECFP) and Venus respectively. In living cells, this probe is highly selective and sensitive to gold and it can withstand changes in variable pH ranges. GolSeN-25, the most efficient sensor variant, binds gold with an affinity (K_d) of 0.3 × 10⁻⁶ M, covering gold concentrations of nM to μM, and can be used for non-invasive real-time in vivo gold measurement in living cells. A simple and sensitive FRET probe was designed for the detection of gold with high selectivity and can be applied to the analysis of real samples.

To study the efflux of gold (Au) in living cells, a genetically encoded fluorescence resonance energy transfer (FRET)-based sensor has been developed.

Kinetics, Thermodynamics and Equilibrium Studies for Gold Recovery from Diluted Waste Solution

2,2′-thiobisethanol dimethacrylate/ethylene glycol dimethacrylate copolymer (coP-TEDMA/EGDMA) was used as a sorbent for gold recovery from residual solutions resulting from the electroplating industry. Firstly, synthesized material was characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and confocal laser scanning microscopy. The sorption process mechanism was evidenced on the basis of kinetic, thermodynamic and equilibrium studies. To highlight this, the influence of solution pH, temperature and gold initial concentration on maximum sorption capacity was studied. The obtained experimental data were modeled using Langmuir, Freundlich and Sips sorption isotherms, and it was observed that the Sips one was better for describing the studied sorption process. Kinetic data were fitted using pseudo-first-order and pseudo-second-order kinetic models. Of these models, the studied process was better described by the pseudo-second-order model. The thermodynamic parameters free Gibbs energy (ΔG0), enthalpy (ΔH0), and entropy (ΔS0) were evaluated on the basis of the van’t Hoff equation. On the basis of the thermodynamic study, it was concluded that gold recovery on coP-TEDMA/EGDMA is a spontaneous and endothermic process.

Full Factorial Design for Gold Recovery from Industrial Solutions

Gold is one of the precious metals with multiple uses, whose deposits are much smaller than the global production needs. Therefore, extracting maximum gold quantities from industrial diluted solutions is a must. Am-L-GA is a new material, obtained by an Amberlite XAD7-type commercial resin, functionalized through saturation with L-glutamic acid, whose adsorption capacity has been proved to be higher than those of other materials utilized for gold adsorption. In this context, this article presents the results of a factorial design experiment for optimizing the gold recovery from residual solutions resulting from the electronics industry using Am-L-GA. Firstly, the material was characterized using atomic force microscopy (AFM), to emphasize the material’s characteristics, essential for the adsorption quality. Then, the study showed that among the parameters taken into account in the analysis (pH, temperature, initial gold concentration, and contact time), the initial gold concentration in the solution plays a determinant role in the removal process and the contact time has a slightly positive effect, whereas the pH and temperature do not influence the adsorption capacity. The maximum adsorption capacity of 29.27 mg/L was obtained by optimizing the adsorption process, with the control factors having the following values: contact time ~106 min, initial Au(III) concentration of ~164 mg/L, pH = 4, and temperature of 25 °C. It is highlighted that the factorial design method is an excellent instrument to determine the effects of different factors influencing the adsorption process. The method can be applied for any adsorption process if it is necessary to reduce the number of experiments, to diminish the resources or time consumption, or for expanding the investigation domain above the experimental limits.

Nanoporous colorant sensors and captors for simultaneous recognition and recovery of gold from E-wastes

Platinum group metals have gained significant interest due to their unique characteristics, which make them the main constituents in advanced applications. In this work, we introduce new pH-dependent optical mesocaptors for the colorimetric monitoring and separation of Au(III) from E-waste leach liquors without a preconcentration process. The mesoporous silica nanospheres are fabricated via simple, reproducible, and low-cost procedures. The optical mesocaptor is designed via indirect immobilization of thiazole yellow G (TYG) and amacid yellow M (AYM) chromogenic probes onto mesoporous nanostructured scaffolds. The silanol groups in the mesopores of silica surface robustly anchored dilauryl dimethyl ammonium bromide (DDAB) linker to induce the interactions with the TYG and AYM chelates, thereby leading to the fashioning of a stable optical mesocaptors without releasing of the chelates throughout adsorption and sensing assays. The finding provides evidence of the capability of the synthesized decorated new nanostructured sensor shows excellent sensitivity toward Au(III) with a limit of detection (LOD) as low as 1.16 µg L^-1. Furthermore, the new sensors were able to selectively detect Au(III) in solution with multi ions components.

Gold (III) adsorption from dilute waste solutions onto Amberlite XAD7 resin modified with L-glutamic acid

The main purpose of this paper was to obtain a material with efficient adsorbing properties and selectivity, to recover the gold (III) from residual diluted solutions resulted from the electroplating process. In this regard, a material was obtained by physico-chemical functionalization of a chemically inert support with functional groups of nitrogen and carboxyl. As a source of functional groups glutamic acid was used, and Amberlite XAD7 type acrylic resin was used as solid support. In order to establish the mechanism of the adsorption process, kinetic, thermodynamic and equilibrium studies were performed. The maximum adsorption capacity of the material has been established, and a gold (III) recovery process has been proposed using thermal decomposition of the exhausted adsorbed material. Main objective of this study was to evaluate an environmental friendly adsorbent material to recover gold from secondary industrial sources.

An ion-imprinted thiocyanato-functionalized mesoporous silica for preconcentration of gold(III) prior to its quantitation by slurry sampling graphite furnace AAS

A gold(III)-imprinted thiocyanato-functionalized silica network of type SBA-15 was prepared by co-condensation of tetraethoxysilane (TEOS) with thiocyanatopropyltriethoxysilane (TCTES) in the presence of Pluronic123 and Au(III) ions. Compared to the non-imprinted material, the imprint has a higher selectivity and adsorption capacity for Au(III). The maximum static adsorption capacity for Au(III) is 475 mg·g⁻¹ for the ion-imprinted, and 62 mg·g⁻¹ for the non-imprinted sorbent. The imprint was applied to the sorption of Au(III) from digested geological samples prior to its determination by graphite furnace atomic absorption spectrometry. Adsorption is fast and does not substantially prolong the analytical procedure. Under optimum conditions, the detection limit for Au(III) is 2 ng·g⁻¹. The method was validated by analyzing certified reference materials, and results were in good agreement with certified values. The procedure was successfully applied to the separation and determination of gold in complex geological samples.

Graphical abstract

Selective Preconcentration of Gold from Ore Samples

A simple and selective method has been developed for preconcentration of gold in ore samples. The method is based on use of N, N-diethyl-N'-benzoylthiourea (DEBT) as selective chelating agent and Amberlite XAD-16 as solid sorbent. Sorption behavior of gold with DEBT impregnated resin under optimized conditions has been studied in batch process. The gold ion capacity of the impregnated resin is calculated as 33.48 mg g⁻¹ resin (0.17 mmol g⁻¹ resin). The selective preconcentration of metal was examined using gold chelates prepared in column process under optimized conditions: pH, flow rate, volume of sample solution, nature of eluent, flow rate, and volume of eluent. Under optimum conditions, gold ions at the concentration of 0.015 μg mL⁻¹ with a preconcentration factor of 6.7 have been determined by flame atomic absorption spectrometry (FAAS). The accuracy of the proposed method was validated by the analysis of a Cu-ore (semi-certified) supplied by CMC (Cyprus Mining Company, North Cyprus) and a certified reference material, Gold Ore (MA-1b Canmet-MMSL). Satisfactory results were obtained with a RSD of 7.6%. The highly selective proposed method does not require any interference elimination process.

Synthesis, characterization and application of cyclam-modified magnetic SBA-15 as a novel sorbent and its optimization by central composite design for adsorption and determination of trace amounts of lead ions

A new, efficient, selective and relatively low cost adsorbent was developed based on Fe₃O₄@cyclam-SBA-15 for adsorption and determination of lead ions.

A sensitive method for the determination of gold and palladium based on dispersive liquid–liquid microextraction combined with flame atomic absorption spectrometric determination using N-(6-morpholin-4-ylpyridin-3-yl)-N′-phenylthiourea

A new method for the determination of gold and palladium was developed by dispersive liquid–liquid microextraction separation-preconcentration and flame atomic absorption spectrometry detection.

Solid-phase extraction of iridium from soil and water samples by using activated carbon cloth prior to its spectrophotometric determination

A solid-phase extraction method for separation and preconcentration of Ir(IV) ion by using activated carbon cloth (ACC) has been presented. Ir(IV) as their 1-(2-pyridylazo) 2-naphtol (PAN) chelate was adsorbed on ACC at pH 2.0 and was eluted from ACC with acidic dimethylformamide (DMF). The Ir(IV) concentration was determined at 536 nm as Ir(IV)-PAN complex by using UV-vis spectrophotometer. The analytical parameters including pH, sample and eluent flow rates, amount of PAN, eluent type, concentration, and sample volume were optimized. The effects of foreign ions on the recoveries of iridium were also investigated. The preconcentration factor was calculated as 60. The limit of detection (LOD) and the limit of quantification (LOQ) of the method were found as 0.039 and 0.129 μg L(-1), respectively. The method was applied to soil and water samples for iridium determination.

Dispersive solid phase microextraction with magnetic graphene oxide as the sorbent for separation and preconcentration of ultra-trace amounts of gold ions

A selective, simple and rapid dispersive solid phase microextraction was developed using magnetic graphene oxide (MGO) as an efficient sorbent for the separation and preconcentration of gold ions. The MGO was synthesized by means of the simple one step chemical coprecipitation method, characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). Gold ions retained by the sorbent were eluted using 0.5mol L(-)(1) thiourea in 0.1mol L(-1) HCl solution and determined by the flow injection flame atomic absorption spectrometry (FI-FAAS). The factors affecting the separation and preconcentration of gold were investigated and optimized. Under the optimized conditions, the method exhibited a linear dynamic range of 0.02-100.0µg L(-)(1) with a detection limit of 4ng L(-1) and an enrichment factor of 500. The relative standard deviations of 3.2% and 4.7% (n=6) were obtained at 20µg L(-1) level of gold ions for the intra and the inter day analysis, respectively. The method was successfully applied to the determination of gold ions in water and waste water samples as well as a certified reference material (CCU-1b, copper flotation concentrate).

Supramolecular solvent-based dispersive liquid–liquid microextraction of copper from water and hair samples

A supramolecular solvent based dispersive liquid–liquid microextraction (SM-DLLME) procedure has been established for the separation and preconcentration of Cu(ii) before its determination by microsampling flame atomic absorption spectrometry.

Fluorescence sensing systems for gold and silver species

Here, we provide an overview of the reported fluorescent detection systems for gold and silver species, and discuss their sensing properties with promising features.

Triethylenetetramine modified multiwalled carbon nanotubes for the efficient preconcentration of Pb(ii), Cu(ii), Ni(ii) and Cd(ii) before FAAS detection

Triethylenetetramine modified multiwalled carbon nanotubes (TETA-MWCNTs) were prepared and used as an efficient adsorbent for the solid phase extraction of heavy metal ions.

Magnetic solid phase extraction of lead(ii) and cadmium(ii) on a magnetic phosphorus-containing polymer (M-PhCP) for their microsampling flame atomic absorption spectrometric determinations

A new magnetic phosphorus-containing polymeric sorbent was successfully used in solid phase extraction for the simple, fast and efficient preconcentration of trace Pb and Cd from environmental water samples.

Supramolecular solvent microextraction of gold prior to its determination by microsample injection system coupled with flame atomic absorption spectrometry

A supramolecular solvent based liquid–liquid microextraction (SsLLME) system for gold was developed prior to its determination by a microsample injection system coupled with flame atomic absorption spectrometric (MS-FAAS).

Tris(2-Aminoethyl)Amine-Functionalized Fe3O4Magnetic Nanoparticles as a Selective Sorbent for Separation of Silver and Gold Ions in Different pHs

The usage of tris(2-aminoethyl)amine-functionalized Fe3O4nanoparticles as a novel magnetic sorbent for rapid extraction, preconcentration, and determination of trace amounts of silver and gold ions was investigated. The optimum conditions for sample pH, eluent parameters (type, concentration and volume) were obtained. The effect of various cationic interferences on the adsorption of silver and gold was evaluated. The analytical efficiency values of both silver and gold ions were higher than 98.0% in the optimum conditions. The limits of detection (LOD) were less than 0.8 and 0.5 ng mL−1for silver and gold, respectively. The linear ranges for silver and gold were 1.5–1000 ng mL−1and 1.0–1000 ng mL−1respectively. The maximum capacity of the modified magnetic nanoparticles was more than 97.3 mg g−1and 167 mg g−1for silver, and gold ions, respectively. The presented method was used to determine silver and gold ions in real samples. Finally, the method accuracy was confirmed by standard reference materials.

Ligandless, ion pair-based and ultrasound assisted emulsification solidified floating organic drop microextraction for simultaneous preconcentration of ultra-trace amounts of gold and thallium and determination by GFAAS

In the present work, a new, simple and efficient method for simultaneous preconcentration of ultra-trace amounts of gold and thallium is developed using an ion pair based-ultrasound assisted emulsification-solidified floating organic drop microextraction procedure before graphite furnace atomic absorption spectrometry determination. This methodology was used to preconcentrate the ion pairs formed between AuCl(4)(-) and TlCl(4)(-) and [C(23)H(42)]N(+) in a microliter-range volume of 1-undecanol. Several factors affecting the microextraction efficiency, such as HCl volume, type and volume of extraction solvent, sonication time, sample volume, temperature, ionic strength and [C(23)H(42)]NCl volume were investigated and optimized. Under the optimized conditions, the enrichment factor of 441 and 443 and calibration graphs of 2.2-89 and 22.2-667 ng L(-1) for gold and thallium were obtained, respectively. The intra- and inter-day precision of ± 4.4 and ± 4.9% for Au and ± 4.8 and ± 5.4% for Tl were obtained. The detection limit was 0.66 ng L(-1) for Au and 4.67 ng L(-1) for Tl. The results show that the liquid-liquid pretreatment using ion pair forming, is sensitive, rapid, simple and safe method for the simultaneous preconcentration of gold and thallium. The method was successfully applied for determination of gold and thallium in natural water and hair samples.

Solid phase extraction of gold(III) on attapulgite modified with triocarbohydrazide prior to its determination in environmental samples by ICP-OES

The first study on the high efficiency of triocarbohydrazide modified attapulgite as solid-phase extractant for preconcentration of trace Au(III) prior to the measurement by inductively coupled plasma optical emission spectrometry (ICP-OES) has been reported. Experimental conditions for effective adsorption of trace levels of Au(III) were optimized with respect to different experimental parameters using batch and column procedures in detail. At pH 3, Au(III) could be quantitatively adsorbed on the new sorbent, and the adsorbed Au(III) could be completely eluted from the sorbent surface by 2.0mL 1.0molL(-1) of HCl+2% CS(NH(2))(2) solution. An enrichment factor of 150 was accomplished. Moreover, common interfering ions did not interfere in both separation and determination. The maximum adsorption capacity of the sorbent for Au(III) was found to be 66.7mgg(-1). The detection limit (3σ) of this method was 0.32μgL(-1) and the relative standard deviation (RSD) was 3.3% (n=8). The method, with high selectivity, sensitivity and reproducibility, was validated using certified reference materials, and had been applied for the determination of trace Au(III) with satisfactory results.