Column preconcentration of gold by adsorbing AuCl<Stack><Subscript>4</Subscript><Superscript>−</Superscript></Stack> onto methyltrioctyl ammonium chloride–naphthalene and subsequent atomic absorption spectrometric determination

A sensitive, selective and simple preconcentration method for ultra-trace gold determination has been developed that uses naphthalene–methyltrioctyl ammonium chloride (Aliquat 336s) as an adsorbent. Gold, in the form of AuCl₄^–, was retained by the adsorbent in the column at a flow rate of 1 ml min^–1. After filtration, the solid mass consisting of the gold complex and naphthalene was dissolved out of the column with 5 ml of N,N-dimethylformamide (DMF), and the metal was then determined by atomic absorption spectrometry. In the initial solution, the calibration graph of absorbance versus gold concentration was found to be linear in the range 0.5–150 ng ml^–1 Au(III) with r=0.997 (n =9), and the 3 s detection limit was 0.428 ng ml^–1. The relative standard deviation for eight replicate measurements of 20 g of gold was 2.14%. Preconcentration factors of 390 and 650 were achieved using 5 ml and 3 ml of DMF, respectively. The proposed method was successfully applied to the determination of gold in wastewater, processed pool water, slurry pool water, and raw well-water from the Moteh gold mine, and synthetic samples.     

Characteristics of subtractive anodic stripping voltammetry of Pb and Cd at silver and gold electrodes

Silver and gold electrodes are useful for the quantitative determination of lead and cadmium with subtractive anodic stripping voltammetry (SASV). The use of SASV is essential for achieving good separation between the two peaks, to eliminate the interference of nitrates when cadmium is present and to allow analysis at very low concentrations without the removal of oxygen. The deposition and dissolution of Pb²⁺ and Cd²⁺ proceed at underpotential (UPD) on both electrodes. The UPD properties of the deposits are the main factor determining the analytical characteristics of the ASV method and are strongly affected by the type and concentration of the electrolyte. The effects of anions (Cl⁻, Br⁻, SO₄²⁻, NO₃⁻) and acids (HNO₃, HClO₄, H₂SO₄, HCl) are shown. The two electrodes complement each other and, in addition, enable the qualitative identification of Pb²⁺ and Cd²⁺, since the peaks appear in opposite order on the two electrodes. Analysis of mixtures of the two analytes is restricted on gold but not on silver. At gold the two peaks overlap: (i) at concentrations of cadmium higher than 250 nM at deposition times greater than 30 s, (ii) in the presence of copper at concentrations higher than 1 μM, and (iii) in the presence of Triton X-100 at concentrations above 10 mg/l. The repeatability at 10 nM analyte is better than 2.5%. The detection limits for Pb²⁺ and Cd²⁺ at 120 s deposition time and 3500 rpm rotation rate are: dl_Pb/Ag=0.04 nM; dl_Cd/Ag=0.7 nM; dl_Pb/Au=0.1 nM; dl_Cd/Au=0.3 nM. The analysis of lead and cadmium in natural waters has been performed.     

Influence of pretreatment conditions on low-temperature CO oxidation over Au/MOx/Al2O3 catalysts

Composite oxide MO_x/Al₂O₃ supported gold catalysts for low-temperature CO oxidation were prepared and investigated. The presence of transition metal oxide was proved to be beneficial to the improvement of catalytic performance of Au/Al₂O₃ catalysts for low-temperature CO oxidation. Furthermore, the influence of various pretreatment conditions on Au/MO_x/Al₂O₃ catalysts was studied carefully. The image of TEM showed that gold catalyst with small gold particles only in the form of a fine dispersion exhibited highly catalytic activity. The XPS, Fourier transform infrared (FTIR) spectroscopy characterization results of Au/FeO_x/Al₂O₃ catalyst showed that gold catalysts having partially oxidized gold species have the best catalytic performance. One possible pathway for CO oxidation on Au/FeO_x/Al₂O₃ catalyst is that the CO adsorbed on gold particles reacts with adsorbed oxygen, which is possible to occur on oxygen vacancies on the support or at the metal–support interface.     

Electrochemical Immunoassay for Carbohydrate Antigen‐125 Based on Polythionine and Gold Hollow Microspheres Modified Glassy Carbon Electrodes

A new electrochemical immunosensor for the detection of carbohydrate antigen‐125 (CA125), a carcinoma antigen, was developed by immobilization CA125 antibody (anti‐CA125) on gold hollow microspheres and porous polythionine (PTH) modified glassy carbon electrodes (GCE). The gold hollow microspheres provided a biocompatible microenvironment for proteins, and greatly amplified the coverage of anti‐CA125 molecules on the electrode surface. The performance and factors influencing the immunosensor were investigated in detail. The detection is based on the current change before and after the antigen‐antibody interaction. Under optimal conditions, the amperometric changes were proportional to CA125 concentration ranging from 4.5 to 36.5 U/mL with a detection limit of 1.3 U/mL (at 3σ). The CA125 immunosensor exhibited good precision, high sensitivity, acceptable stability, accuracy and reproducibility. The as‐prepared immunosensors were used to analyze CA125 in human serum specimens. Analytical results suggest that the developed immunoassay has a promising alternative approach for detecting CA125 in the clinical diagnosis.     

Differing Coordination Modes of (O‐Alkyl)‐p‐Ethoxyphenyldithiophosphonato Ligands in Copper(I), Silver(I) and Gold(I) Triphenylphosphine Complexes

The three (O‐methyl)‐p‐ethoxyphenyldithiophosphonato triphenylphosphine complexes of copper, silver and gold, [(Ph₃P)_nM{S₂P(OMe)C₆H₄OEt‐p}] (M = Cu, n = 2; M = Ag, Au, n = 1) investigated structurally by X‐ray diffraction exhibit remarkable structural differences. The copper compound is a four‐coordinate chelate monomer with Cu–S 2.4417(6) and 2.5048(6) Å; P–Cu–S 104.24(2)–114.01(2)°; Cu–S–P 82.49(3)° and 80.85(2)°. The silver compound is a cyclic dimer with bridging dithiophosphonato ligands and three‐coordinate silver atoms [Ag–S 2.5371(5) and 2.6867(5) Å; P–Ag–S 122.88(2)° and 122.17(2)°; Ag–S–P 89.32(2)° and 103.56(2)°]. The gold compound is monomeric with linear dicoordinate gold [Au–S 2.3218(6) Å; P–Au–S 177.72(2)°, Au–S–P 100.97(3)°].     

纳米金标记电化学检测DNA特异性结合蛋白

将单分子发夹寡核苷酸固相延伸形成双链寡核苷酸, 以纳米金颗粒标记NF-κB并银染放大, 采用阳极溶出电位法对NF-κB进行检测. 结果表明, 本法检测序列特异性蛋白质具有高度特异性、高灵敏度和快速等特点, 为转录因子调控机制、开放阅读框识别和功能基因检测等的研究提供了有利工具.     

泡沫塑料动态快速分离富集金方法的研究

本文系统研究了泡沫塑料动态快速分离富集金的方法。对泡沫塑料柱的处理方法,再生及主要共存离子干扰的消除等均做了较详细的研究。提出了一种简便,不控速的金分离富集的方法。该法用于分析0.051～3.59g/t四种不同含量的金标样,结果与推荐值吻合,5次分析结果,相对标准偏差<5％,同时,可用泡沫塑料柱当天连续使用分析拿标样,回收率为93％—109％。     

马家塔矿煤层中有害痕量元素的质量分数特性

应用仪器中子活化（INAA）、电感耦合等离子体原子发射光谱（ICP AES）和原子吸收光谱（AAS）对神华集团马家塔露天矿2-2#煤层中Hg、As、Se、Pb、Be、Cr、Cd、Ni、Th、U、Mn、Mo、Co、Sb和Br共15种有害痕量元素的质量分数进行测定。结果表明，绝大部分痕量元素的质量分数都明显低于中国煤中元素质量分数的平均值，只有Hg和Mn的质量分数偏高，其中Hg的质量分数异常高；通过分析痕量元素在煤层垂向剖面上的质量分数变化特性，揭示出痕量元素在煤层中分布的非均一性,分析了影响痕量元素分布与富集的因素；通过痕量元素之间以及与黄铁矿硫、Fe、Al、Ca、P的聚类分析，研究了痕量元素之间以及与煤中不同矿物组分之间的亲和特性。     

DNA在纳米金标上的组装、杂交、检测与银增强

利用电化学方法进行DNA的杂交检测.将目标ss-DNA固定在玻碳电极表面, 使其与纳米金标记的互补DNA发生杂化反应, 通过银增强试剂（该种试剂可以使银在纳米金表面沉积, 达到信号增强的效果）在纳米金上沉积银, 形成银包金的核壳结构.在酸性介质中沉积的银被氧化释放, 以离子状态存在于溶液中.用阳极溶出伏安法(ASV)检测银离子从而达到间接检测目标DNA的目的.测定结果表明，ss-DNA的浓度在100～1 000 pmol•L－1 范围内有非常好的线性关系, 检测限为10 pmol•L－1.     

Revisiting catechol derivatives as robust chromogenic hydrogen donors working in alkaline media for peroxidase mimetics

Colloidal noble metal-based nanoparticles are able to catalyze oxidation of chromogenic substrates by H₂O_2, similarly to peroxidases, even in basic media. However, lack of robust chromogens, which work in high pH impedes their real applications. Herein we demonstrate the applicability of selected catechol derivatives: bromopyrogallol red (BPR) and pyrogallol (PG) as chromogenic substrates for peroxidase-like activity assays, which are capable of working over wide range of pH, covering also basic values. Hyperbranched polyglycidol-stabilized gold nanoparticles (HBPG@AuNPs) were used as model enzyme mimetics. Efficiency of several methods of improving stability of substrates in alkaline media by means of selective suppression of their autoxidation by molecular oxygen was evaluated. In a framework of presented studies the impact of borate anion, applied as complexing agent for PG and BPR, on their stability and reactivity towards oxidation mediated by catalytic AuNPs was investigated. The key role of high concentration of hydrogen peroxide in elimination of non-catalytic oxidation of PG and improvement of optical properties of BPR in alkaline media containing borate was underlined. Described methods of peroxidase-like activity characterization with the use of BPR and PG can become universal tools for characterization of nanozymes, which gain various applications, among others, they are used as catalytic labels in bioassays and biosensors.