Study on Determination of Trace Nickel in Water Samples after Separation/enrichment using Microcrystalline Phenolphthalein Loaded with Chelate

The paper presents a novel method for the separation/enrichment of trace Ni²⁺ using microcrystalline phenolphthalein loaded with chelate prior to the determination by spectrophotometry. The effects of different parameters, such as the dosages of phenolphthalein and sodium diethyldithiocarbamate (DDTC), various salts and acidity on the enrichment yield of Ni²⁺ have been investigated to select the experimental conditions. The possible enrichment mechanism of Ni²⁺ was discussed. The results showed that under the optimum conditions, Ni²⁺ could be quantificationally adsorbed on the surface of microcrystalline phenolphthalein in the form of the chelate precipitate of Ni(DDTC)₂, while K⁺, Na⁺, Ca²⁺, Mg²⁺, Zn²⁺, Fe²⁺, Al²⁺, Pb²⁺ and Cd²⁺ could not be adsorbed at all. Therefore, Ni²⁺ was completely separated from the above metal ions in the solution. A new method for the separation/enrichment and determination of trace nickel using microcrystalline phenolphthalein loaded with chelate was established. The proposed method has been successfully applied to the determination of Ni²⁺ in various water samples, and the results agreed well with those obtained by FAAS method.     

Research on photosensitivity of benzoquinones and benzoquinoneimines in the sunlight/Fe<Superscript>2+</Superscript>/S<Subscript>2</Subscript>O<Subscript>8</Subscript><Superscript>2−</Superscript> system

This paper investigated the photodegradation characteristics of benzoquinones and benzoquinoneimines. The photosensitivity of benzoquinones and benzoquinoneimines were analyzed by measuring the yield of SO ₄ ^?· in a light/Fe²⁺/S₂O₈ ^2? system and the degradation mechanism of benzoquinones, then discussed benzoquinoneimines in light/Fe²⁺/S₂O₈ ^2? and light/S₂O₈ ^2? system. The results revealed that a more aggressive oxidation of benzoquinones and benzoquinoneimines by the sunlight/Fe²⁺/S₂O₈ ^2? method showed a more rapid and more complete removal of chromaticity than that of the UV/Fe²⁺/S₂O₈ ^2? method. It was showed that they were photosensitizers, and they could generate ¹O₂ and O ₂ ^?· which could promote the formation of SO ₄ ^?· and ^·OH in the sunlight system. Nevertheless, for benzoquinones, the sunlight/S₂O₈ ^2? method was superior to the UV/S₂O₈ ^2? method. For benzoquinoneimines, the sunlight/S₂O₈ ^2? method was inferior to the UV/S₂O₈ ^2? method. In addition, the yield of SO ₄ ^?· in the sunlight/Fe²⁺/S₂O₈ ^2? system was more than that of the UV/Fe²⁺/S₂O₈ ^2? system. Therefore, the photosensitivity of benzoquinones is superior to benzoquinoneimines in water treatment.     

Determination of Cu2+ in Drinking Water Based on Electrochemiluminescence of Ru(phen)32+ and Cyclam

A convenient and simple electrochemiluminescence (ECL) method was employed to detect trace amounts of Cu²⁺ in drinking water. This method is based on the inhibitory effect of Cu²⁺ on the ECL of Ru(phen)₃²⁺ and 1,4,8,11‐tetraazacyclotetradecane (cyclam) system. ECL intensity of Ru(phen)₃²⁺ was considerably enhanced by the addition of cyclam because of the ECL reaction between them. The ECL intensity of Ru(phen)₃²⁺/cyclam system rapidy decreased with the addition Cu²⁺ because of the formation of chelate complex [Cu(cyclam)]²⁺. Good linear response (R ²=0.9948) was obtained at Cu²⁺ concentration of 1.0×10⁻⁹−1.0×10⁻⁵ mol ⋅ L⁻¹ at glassy carbon electrode in 0.1 mol ⋅ L⁻¹ phosphate buffer (pH 9.0). Observed detection limit of 4.8×10⁻¹⁰ mol ⋅ L⁻¹ satisfied the maximum contaminant level goal (MCLG) for Cu²⁺ set by the US Environmental Protection Agency (US EPA). Applicability of the proposed method was verified by the good reproducibility and stability of the method when applied to determine Cu²⁺ in tap water and simulated wastewater. Thus, a novel ECL detection method was developed for Cu²⁺ detection.     

Evaluation of Gibbs free energy for the transfer of a highly hydrophilic ion from an acidic aqueous solution to an organic solution based on ion pair extraction

A method to determine the standard Gibbs free energy for the transfer, ΔG°_tr, of a highly hydrophilic metal ion from an aqueous solution, W, in the presence of high concentration of H⁺ to an organic solution, O, was proposed based on the theoretical consideration of the distribution process of ions between W and O. The usefulness of the proposed method was verified experimentally by comparing ΔG°_tr of Mg²⁺ determined by the method with that obtained by voltammetry for the ion transfer at the W|O interface. The O examined were nitrobenzene (NB) and 1,2-dichloroethane (DCE). By applying the proposed method, ΔG°_tr of NpO₂⁺, UO₂²⁺, NpO₂²⁺ and PuO₂²⁺ from an acidic W to NB were determined.     

Halbquantitative analyse durch messung der entfärbungs-zeit von tüpfelflecken

A rapid semiquantitative method is described based on measurement of the time required for decolorization of spotreactions on filter paper strips by suitable reagents, This very simple method yields results which are accurate to ± 10%. The method has been verified for several ions (Ag⁺, Pb²⁺, JO₃^-,Cu²⁺, CrO₄^2-). The utility of this method for the characterization and differentiation of filter papers is indicated.     

Electrochemical Quantification of Lead Adsorption on TiO2 Nanoparticles

This work describes a rapid easy-to-use electrochemical method for quantifying lead (Pb²⁺) adsorption on metal oxide nanoparticles (NPs), demonstrated here for titanium dioxide (TiO₂). The method was able to quantify Pb²⁺ adsorption for concentrations as low as 0.95 μM, and up to 200 μM in NP dispersions, and to differentiate ion uptake in the presence and absence of a natural organic material, humic acid (HA). The method was selective for Pb²⁺ against Cu²⁺, As³⁺, Zn²⁺, Cd²⁺ and Cr³⁺ ions when measured in the specific potential range from −0.4 to −0.6 V and was successfully demonstrated in water and home-collected dust.     

Preconcentration and Determination of Trace Amounts of Heavy Metals in Water Samples Using Membrane Disk and Flame Atomic Absorption Spectrometry

A fast and simple method for preconcentration of Ni^2＋, Cd^2＋, Pb^2＋, Zn^2＋, Cu^2＋ and Co^2＋ from natural water samples was developed. The metal ions were complexed with sodium diethyldithiocarbamate （Na-DDTC）, then adsorbed onto octadecyl silica membrane disk, recovered and determined by FAAS. Extraction efficiency, influence of sample volume and eluent flow rates, effects of pH, amount of Na-DDTC, nature and amount of eluent for elution of metal ions from membrane disk, break through volume and limit of detection have been evaluated. The effect of foreign ions on the percent recovery of heavy metal ions has also been studied. The limit of detection of the proposed method for Ni^2＋, Cd^2＋, Pb^2＋, Zn^2＋, Cu^2＋ and Co^2＋was found to be 2.03, 0.47, 3.13, 0.44, 1.24 and 2.05 ng·mL^-1, respectively. The proposed （DDTC） method has been successfully applied to the recovery and determination of heavy metal ions in different water samples.     

Spectrophotometric microdetermination of iron(III) by tris-pyrrolidone(5)-hydroxamato(2)-chelate

The optimum conditions for the spectrophotometric determination of iron(III) with neutrial tris-PIH-chelate are: pH = 5, λ = 430 nm, PIH concentration 2 × 10⁻² M, and iron (III) concentration (0.6–3.3) × 10⁻⁴ M. Under these conditions the suggested method conforms to Beer's law and the molar absorptivity is 2800. The relative accuracy is ±0.48% based upon evaluation from the calibration curve and ±1.02% based upon algebraic equations. The precision is ±0.53% as deviation from the mean, and 0.69% as SD.The suggested method suffers from no interference from Fe²⁺, Al³⁺, Cr³⁺, Pb²⁺, Hg²⁺, Cd²⁺, Ni²⁺, Co²⁺, Zn²⁺, Mn²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Mg²⁺, Ag⁺, F⁻, and tartrate, but interference is caused by U⁶⁺, V⁵⁺, Mo²⁺, Cu²⁺, (in larger concentrations) or by oxalate and citrate. The method may be used either as a sensitive spectrophotometric or visual method.     

Highly selective colorimetric naked-eye Cu2+ detection using new bispyrazolone silver nanoparticle-based chemosensor

In this work, we have successfully developed novel silver nanoconjugates of pyrazolone analogue and screened its chemosensing potential in aqueous medium. Bispyrazolone silver nanoparticles (Bispyra-AgNPs) were synthesised and characterised through FTIR, UV-visible spectroscopy and atomic force microscopy. The sensing ability was explored towards Ca²⁺, Cd²⁺, Co²⁺, Cu²⁺, Fe²⁺, Li⁺, Pb²⁺, La³⁺, Hg²⁺, Mg²⁺, Ni²⁺ and Ba²⁺ metal ions, respectively. Bispyra-AgNPs showed a highly quenching potential in selective recognition of Cu²⁺and colour of the solution immediately turned from yellow to purple, after the addition of Cu²⁺ in to the solution. The developed method also displayed a remarkable selectivity for Cu²⁺ over others interfering metal ions. The binding ratio and stoichiometry of host-guest complex was found to be 1:1 and determined by Job’s method. The propose method is facile and sensitive to detect Cu²⁺ with detection limit of 10 µM.     

Atomic absorption determination of nicotine in tobacco

A new method for the determination of nicotine alkaloid has been developed. This method is based on the quantitative precipitation of the alkaloid with metals such as Cu²⁺, Pb²⁺, Zn²⁺ and Hg²⁺. Then either the equivalent or residual metal is determined.The proposed method was successfully applied to the determination of nicotine in various types of tobaccos.     

负载型纳米二氧化钛对重金属离子吸附性能的研究

采用溶胶-凝胶法制备二氧化钛溶胶, 将其浸渍在硅胶上, 合成了负载型纳米二氧化钛材料, 以X射线衍射(XRD)、扫描电镜(SEM)等手段对其进行了表征. 以ICP-AES为检测手段, 系统地研究了负载型纳米TiO₂材料对重金属离子Cd^2＋, Cr^3＋, Cu^2＋和Mn^2＋的吸附性能. 结果表明, 在pH 8～9范围内, 所研究的重金属离子均可被定量富集, 吸附的金属离子可用0.5 mol/L的HNO₃完全解脱. 负载型纳米二氧化钛对Cd^2＋, Cr^3＋, Cu^2＋和Mn^2＋的静态吸附容量分别为8.3, 13.1, 12.6和5.1 mg/g, 与未负载的纳米二氧化钛相近. 将其应用于环境标准样品中Cd^2＋, Cr^3＋, Cu^2＋和Mn^2＋的分离富集与测定, 结果满意.     

Simultaneous determination of zinc and copper(II) with 1-(2-pyridylazo)2-naphthol in micellar media by spectrophotometric H-point standard addition method

The H-point standard addition method (HPSAM) was applied to handling spectrophotometric data for simultaneous determination of Zn²⁺ and Cu²⁺ or selective determination of Zn²⁺ in the presence of Cu²⁺. The ligand 1-(2-pyridylazo)2-naphthol (PAN) and its metal complexes (Zn-PAN and Cu(II)-PAN) were made water-soluble by the neutral surfactant Triton X-100, and therefore, no extraction with organic solvents was required. The method is based on the difference in absorbance of formed complexes between Zn²⁺ and PAN, at two different wavelengths at pH = 9.2. The formation of both the complexes was complete within five minutes. Zn²⁺ can be determined in the range of 0.2–25 μg/mL with satisfactory accuracy and precision in the presence of excess of Cu²⁺ and most other metal ions. Interference effects of common anions and cations were studied. Under working conditions, the proposed method was successfully applied to the simultaneous determination of Zn²⁺ and Cu²⁺ in several real and synthetic mixtures with different concentration ratio of Zn²⁺ and Cu²⁺. The text was submitted by the authors in English.     

Studies on the hydrolytic polymerization of chromium (III) ion: IX. Revision of graphical method for the reaction in the presence of maleic acid by computer

The hydrolytic polymerization of Cr²⁺ in the presence of maleic acid was studied by equilibrium pH method at 60°C and constant ionic strength. Both maleic acid and Cr³⁺ are of three different concentrations: 0.006, 0.008, 0.01 mol·L^?1. The state of Cr³⁺ in aqueous solution were determined by graphical method and pqr analysis. The following species were found (CrA)^+, Cr-(OH)A and Cr₂(OH)₂A₂. The results by graphical method were revised by computer calculation with data of about fifty experimental points. Hydrolysis constants of all species were obtained with good fitting. It is obvious that the results obtained by program LEMIT are more accurate than those by graphical method. Mechanism of Cr³⁺ polymerization in the presence of maleic acid is also discussed.     

Determination of calcium and magnesium in magnesite by a complexometric method employing co-precipitation of calcium with strontium sulphate

In the classical gravimetric method calcium is precipitated as phosphate along with the magnesium and recovered by adding sulphuric acid and alcohol, then Ca²⁺ and Mg²⁺ are determined separately by the usual method [1]. In the proposed method calcium is co-precipitated with strontium sulphate and in the filtrate magnesium ions are determined by EDTA. Then calcium is calculated by difference after estimating combined Ca²⁺ and Mg²⁺ ions [2].     

Simultaneous Determination of Iron and Copper in Ethanol Fuel Using Nafion/Carbon Nanotubes Electrode

This work presents the analytical method development for iron and copper determination in ethanol fuel. This method was developed using stripping voltammetry with a glassy carbon electrode modified with Nafion/Carbon‐nanotubes. With linear sweep stripping voltammetry was achieved a limit of detection of 7.1×10^?7 mol L^?1 for Fe³⁺ and 5.1×10^?8 mol L^?1 for Cu²⁺. The amperometric sensitivities were 2.0×10⁶ µA mol^?1 L for Fe³⁺ and 2.8×10⁷ µA mol^?1 L for Cu²⁺. The recovery study showed that the method has good accuracy and repeatability, with recovery of 108 and 103 % for Fe³⁺ and Cu²⁺ respectively.     

Study on Separation/Enrichment and Determination of Mercury(II) using Microcrystalline Thymolphthalein Loaded with Ternary Association Complex

The paper presents a novel method for the separation/enrichment of Hg²⁺ using microcrystalline thymolphthalein loaded with ternary association complex prior to the determination by spectrophotometry. The effects of different parameters, such as the dosages of KI and dodecyl trimethyl ammonium bromide (DTAB) and thymolphthalein, various salts and acidity etc. on the enrichment yield of Hg²⁺ have been investigated to select the experimental conditions. The results showed that in the presence of 1.0 g NaCl, when the dosage of 0.1 M KI solution was 1.50 mL and 5.0 × 10⁻³ M dodecyl trimethyl ammonium bromide (DTAB) solution was 1.50 mL respectively, the water‐insoluble ternary association complex of (DTAB)₂(HgI₄) which produced by Hg²⁺ and I⁻, DTAB cation (DTAB⁺) was quantificationally absorbed on the surface of microcrystalline thymolphthalein Therefore, Hg²⁺ was separated completely from Zn²⁺, Mn²⁺, Ni²⁺, Co²⁺, Fe³⁺, Al³⁺, Pb²⁺, Bi³⁺ and Cr³⁺ etc. by contolling acidity. The possible enrichment mechanism of Hg²⁺ was deduced. The proposed method has been successfully applied to the determination of Hg²⁺ in the sample of industrial waster water, and the results agreed well with the dithizone method. The recoveries were 94.5%∼106.5%, and the RSD was 2.0%∼2.8%.     

Lower oxidation states of lanthanides and actinides. Prospects of their use in analytical practice

Physico-chemical characteristics of Ln²⁺ and An²⁺ such as standard oxidation potentials E_M ³⁺M²⁺, hydration energies, ionic radii were obtained by the cocrystallization method. A number of energy parameters for Ln²⁺ and U³⁺ were obtained by optical spectroscopy on the basis of fd-spectra in such solvents as H₂O, C₂H₅OH, HMPA, THP and others. A new rapid method has been developed to extract higher actinides and separate them from similar elements by cocrystallization with NaCl from aqueous ethanolic solutions.     

Au/Ag2S dimeric nanostructures for highly specific plasmonic sensing of mercury(Ⅱ)

Although many plasmonic nanosenosrs have been established for the detection of mercury(Ⅱ)(Hg²⁺),few of them is feasible for analyzing natural samples with very complex matrices because of insufficient method selectivity.To address this challenge,we propose an epitaxial and lattice-mismatch approach to the synthesis of a unique Au/Ag₂S dimeric nanostructure,which consists of an Au segment with excellent plasmonic characteristics,and a highly stable Ag₂S portion wi...     

Buffer gas effect on monitoring I2 by a laser induced fluorescence method

Based on the measured N₂ pressure dependence of high resolution fluorescence excitation spectra for ¹²⁷I₂ near the He-Ne laser frequency, effects of the N₂ pressure on the I₂ detection limit and isotopic selectivity of an on-line I₂ monitor using a laser induced fluorescence method are discussed. A possible influence from NO₂, which is contained in reprocessing off-gas streams, on monitoring I₂ is also examined. The ¹²⁷I₂ in N₂ at atmospheric pressure is detected down to a concentration of 5 × 10¹² molecules cm⁻³ by a ³He-²⁰Ne laser induced fluorescence method.     

Qualitative and quantitative 1H NMR spectroscopy for determination of divalent metal cation concentration in model salt solutions,food supplements,and pharmaceutical products by using EDTA as chelating agent

This paper introduces an ¹H NMR method to identify individual divalent metal cations Be²⁺, Mg²⁺, Ca²⁺, Sr²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Sn²⁺, and Pb²⁺ in aqueous salt solutions through their unique signal shift and coupling after complexation with the salt of ethylenediaminetetraacetic acid (EDTA). Furthermore, quantitative determination applied for the divalent metal cations Ca²⁺, Mg²⁺, Hg²⁺, Sn²⁺, Pb²⁺, and Zn²⁺ (limit of quantification: 5–22 μg/ml) can be achieved using an excess of EDTA with aqueous model salt solutions. An internal standard is not required because a known excess of EDTA is added and the remaining free EDTA can be used to recalculate the quantity of chelated metal cations. The utility of the method is demonstrated for the analysis of divalent cations in some food supplements and in pharmaceutical products.