Treated Rice Bran for Scavenging Cr(III) and Hg(II) from Acidic Solution

The purpose of this study was to examine the efficiency with which rice bran (treated or untreated) removes heavy metals, especially Cr(III) and Hg(II), from acidic solution. Sorption assays were done in shaken flasks in the presence of rice bran. Different experimental conditions such as pH, volume of solution, bran weight, particle size, exchange time and stirring time were improved. The efficiency of bran was studied before and after treatments. For treatment, solutions of acid, alkali and salt were used. The results show that after treating with 4 M sodium chloride solution, its efficiency in removal of Cr(III) and Hg(II) was improved. Kinetic measurements of chromium and mercury removal by bran have revealed that sorption equilibrium was obtained after 10 min of contact. Sorption experiments done with various granulometric fractions of rice bran have shown that this sorbent has the same efficiencies in meshes higher than 20. Further research is necessary in order to determine a mechanism for cations removal by the bran. It is mentioned that the process of making polished rice from brown rice discharges rice bran; therefore, it is very inexpensive, with a cost of 1/50 ? 1/40 of that of synthetic sorbent, and thus its use would significantly lower the cost of wastewater treatment.     

DMA-80测汞仪的应用探讨

本文的主要实验目的是利用DMA-80测汞仪直接测定固体样品中的汞并证明其方法可靠。采用升温加热直接进行热分解、金汞齐反应,采用长、短双检测池,可直接测定固体、液体样品,汞含量在0.n×10-9～600.0×10-9范围内的样品都能被很准确地测定,每个样品测定时间约为5min。 测试结果证明其方法具可靠性。     

ICP-AES法测定烟花爆竹药物中的砷、汞、铅

为了禁止含砷、汞、铅物质应用到烟花爆竹药物中,建立ICP-AES方法,在烟花爆竹药物经乙醇、丙酮及硝酸处理后,选用As 189.042 nm、Hg 194.227 nm、Pb 220.353 nm分析线同时测定这3种元素的含量,结果:相对标准偏差为1.97%~2.71%,回收率为98.5%~101%.方法操作简单快速,检出限低、干扰小,结果准确可靠.     

一种裸眼识别Cu~(2+)和Hg~(2+)传感器的合成与性质研究

设计合成了一种香豆素修饰的罗丹明类衍生物L,用作程序型Cu2+与Hg2+检测传感器。采用核磁共振谱、高分辨质谱、红外光谱对其结构进行了表征。利用紫外光谱考察L对不同金属离子的识别作用,研究发现L可以高选择性和高灵敏度识别Cu2+。向L溶液中加入不同的金属离子时(Zn2+,Hg2+,Cu2+,Fe3+,Cd2+,Co2+,Ni 2+,Mg2+,Ca2+,Al 3+,La3+,K+,Na+,Mn2+,Pb2+和Ag+),只有Cu2+的加入会使溶液由无色变为粉色,并且在534nm出现一个新的吸收峰,说明传感器L可以裸眼识别Cu2+。通过紫外滴定得到L可以识别Cu2+的最低检测限为1.9×10-8 mol·L-1。制备了基于L的Cu2+检测试纸,该试纸可以方便快捷的检测水中的Cu2+。通过Job’s曲线和高分辨质谱确定了配合物L-Cu2+之间的结合比为1∶1。另外,若向L-Cu2+的DMSO溶液中加入1equiv.EDTA,溶液瞬间由粉色变为无色,说明EDTA可以取代L并与Cu2+结合,因此传感器L识别Cu2+是可逆的。另外,向L-Cu2+的配合物中加入Hg2+,溶液会由粉色变为无色(而加入其他阳离子没有明显变化),这可顺序实现对Hg2+的裸眼识别。通过紫外滴定计算出L-Cu2+识别Hg2+的最低检测限为2.9×10-7 mol·L-1。因此该程序型传感器L可以有序的裸眼识别Cu2+和Hg2+。     

Determination of Hg by on-line separation and pre-concentration with atmospheric-pressure solution-cathode glow discharge atomic emission spectrometry

A simple and sensitive method to determine Hg²⁺ was developed by combining solution-cathode glow discharge atomic emission spectrometry (SCGD-AES) with flow injection (FI) based on on-line solid-phase extraction (SPE). We synthesized l-cysteine-modified mesoporous silica and packed it in an SPE microcolumn, which was experimentally determined to possess a good mercury adsorption capacity. An enrichment factor of 42 was achieved under optimized Hg²⁺ elution conditions, namely, an FI flow rate of 2.0 mL min⁻¹ and an eluent comprised of 10% thiourea in 0.2 mol L⁻¹ HNO₃. The detection limit of FI–SCGD-AES was determined to be 0.75 μg L⁻¹, and the precision of the 11 replicate Hg²⁺ measurements was 0.86% at a concentration of 100 μg L⁻¹. The proposed method was validated by determining Hg²⁺ in certified reference materials such as human hair (GBW09101b) and stream sediment (GBW07310).     

Direct determination of total mercury in phosphate rock using alkaline fusion digestion

The aim of this work was to develop a new method to determine the mercury (Hg) concentrations in phosphate rock using a dedicated analytical instrument (the DMA80 Tricell by Milestone) that employs an integrated sequence of thermal decomposition followed by catalyst conversion, amalgamation and atomic absorption spectrophotometry. However, this instrument underestimates Hg concentrations when phosphorite and apatite rocks are investigated with a classic thermal decomposition treatment that complies with US EPA method 7473.     

Sensitive pseudobienzyme electrocatalytic DNA biosensor for mercury(II) ion by using the autonomously assembled hemin/G-quadruplex DNAzyme nanowires for signal amplification

Herein, a novel sensitive pseudobienzyme electrocatalytic DNA biosensor was proposed for mercury ion (Hg²⁺) detection by using autonomously assembled hemin/G-quadruplex DNAzyme nanowires for signal amplification. Thiol functionalized capture DNA was firstly immobilized on a nano-Au modified glass carbon electrode (GCE). In presence of Hg²⁺, the specific coordination between Hg²⁺ and T could result in the assembly of primer DNA on the electrode, which successfully triggered the HCR to form the hemin/G-quadruplex DNAzyme nanowires with substantial redox probe thionine (Thi). In the electrolyte of PBS containing NADH, the hemin/G-quadruplex nanowires firstly acted as an NADH oxidase to assist the concomitant formation of H₂O₂ in the presence of dissolved O₂. Then, with the redox probe Thi as electron mediator, the hemin/G-quadruplex nanowires acted as an HRP-mimicking DNAzyme that quickly bioelectrocatalyzed the reduction of produced H₂O₂, which finally led to a dramatically amplified electrochemical signal. This method has demonstrated a high sensitivity of Hg²⁺ detection with the dynamic concentration range spanning from 1.0 ng L⁻¹ to 10 mg L⁻¹ Hg²⁺ and a detection limit of 0.5 ng L⁻¹ (2.5 pM) at the 3S_blank level, and it also demonstrated excellent selectivity against other interferential metal ions.     

Direct determination of mercury in cosmetic samples by isotope dilution inductively coupled plasma mass spectrometry after dissolution with formic acid

A new method was proposed for the accurate determination of mercury in cosmetic samples based on isotopic dilution (ID)-photochemical vapor generation (PVG)-inductively coupled plasma mass spectrometry (ICP MS) measurement. Cosmetic samples were directly dissolved in formic acid solution and subsequently subjected to PVG for the reduction of mercury into vapor species following by ICP MS detection. Therefore, the risks of analyte contamination and loss were avoided. Highly enriched ²⁰¹Hg isotopic spike is added to cosmetics and the isotope ratios of ²⁰¹Hg/²⁰²Hg were measured for the quantitation of mercury. With ID calibration, the influences originating from sample matrixes for the determination of mercury in cosmetic samples have been efficiently eliminated. The effects of several experimental parameters, such as the concentration of the formic acid, and the flow rates of carrier gas and sample were investigated. The method provided good reproducibility and the detection limits were found to be 0.6 pg mL⁻¹. Finally, the developed method was successfully applied for the determination of mercury in six cosmetic samples and a spike test was performed to verify the accuracy of the method.     

A specific and ratiometric chemosensor for Hg based on triazole coupled ortho-methoxyphenylazocalix[4]arene

Calix[4]arene 3, which contains two distal triazole groups on the lower rim and two distal o-methoxyphenylazo groups on the upper rim, was synthesized and found to be a specific and ratiometric sensor for Hg²⁺ in a polar protic solvent. A series of o-methoxyphenylazo derivatives (3, 4, 5, 7, and 9) were synthesized, which proved that the lower-rim triazoles and the hydroxyl azophenol(s) were the major ligands for metal ion binding. Though analogues 4 and 10 showed some sensitivity for Hg²⁺, compound 3 was the only ratiometric chemosensor for Hg²⁺ among the series of azocalix[4]arenes synthesized in this work. The formation of 3·Hg²⁺ complex was supported by UV/vis and NMR titration studies and Mass spectrometry. Based on the symmetrical features of NMR spectra of 3·Hg²⁺, the complex is believed to be symmetrical with respect to the calix[4]arene cavity. Furthermore, the complex was determined to be 1:1 binding stoichiometry by Job’s plot, and the association constant was determined to be 4.02×10³ M⁻¹ using Benesi-Hildebrand plot.     

Synthesis and spectral characterization of mercury(II) complexes with the bidentate Schiff base ligand N,N′-bis(2,3-dimethoxybenzylidene)-1,2-diaminoethane: The crystal structures of [Hg((23-MeO-ba)2en)I2] and [Hg((23-MeO-ba)2en)Br2]

Three mercury(II) complexes, [Hg((23-MeO-ba)₂en)X₂] (X = I (1), Br (2) and Cl(3)), and the ligand (23-MeO-ba)₂en ((23-MeO-ba)₂en = N,N′-bis(2,3-dimethoxybenzylidene)-1,2-diaminoethane) have been synthesized and characterized by elemental analyses, FT-IR and ¹H NMR spectroscopy. The crystal and molecular structures of 1 and 2 were determined by X-ray crystallography from single-crystal data. The metal-to-ligand ratio was found to be 1:1. The mercury(II) center in 1 and 2 has a distorted tetrahedral geometry with HgN₂I₂ and HgN₂Br₂ chromophores, respectively. The Schiff base ligand (23-MeO-ba)₂en acts as a chelating ligand, coordinating via the two nitrogen atoms to the mercury(II) center, and it adopts an E,E conformation. The coordination sphere of the mercury(II) center in 1 and 2 is completed by the two I and Br atoms, respectively. In complex 1 an inter-molecular non-classical hydrogen bond of the type C-H?O was found, while in complex 2 inter- and intra-molecular non-classical hydrogen bonds of the type C-H?X (X = O and Br) were found. The ¹H NMR spectra of the complexes exhibit downfield as well as upfield shifts of the free ligand resonances, reflecting changes in the ligand’s geometry during its coordination.