Determination of micromolar concentrations of cyanide in solution with a piezoelectric detector

The silver plated electrodes of a piezoelectric quartz crystal are partly dissolved by cyanide in pH 9.6 solution during a 15-min immersion. The resulting frequency change of the crystal, measured in air, is proportional to cyanide concentration over the range 10^-7–10^-5 M.     

Determination of lead by adsorption of the extracted 8-quinolinolate on the electrodes of a piezoelectric quartz crystal

Lead 8-quinolinolate extracted into chloroform is adsorbed on the electrodes of a piezoelectric quartz crystal. The change in frequency of the crystal is used to measure the lead concentration over the range 3 × 10^-6–5 × 10^-5 M in aqueous solution. The interferences of Fe(III), Ni, Co(II), Zn, Cd and Ag(I) can be masked byl-ascorbic acid and cyanide.     

Electrolytic determination of nanomolar concentrations of silver in solution with a piezoelectric quartz crystal

Silver in solution is determined in situ by the frequency change of a piezoelectric quartz crystal on electrodeposition on the electrode of the crystal. The electrolyte solution flows through a cell containing the platinum-plated electrode (cathode) of the quartz crystal, a coiled platinum-wire anode and a silver—silver(I) chloride reference electrode, and is electrolyzed at —0.2 V vs. $\text{Ag}\text{AgCl}$. The frequency change is proportional to the silver concentration in the range 10^-5–5 × 10^-7 M after electrodeposition for 5 min, and in the range 10^-8–10^-9 M by recycling 20 ml of the solution over the electrodes for 3 h.     

Determination of silver in solution with a piezoelectric detector after electrodeposition

Silver in solution is determined in situ by frequency change of a piezoelectric quartz crystal due to electrodeposition on the electrode of the crystal immersed in the solution. A test solution containing EDTA for masking other metal ions flows through a thermostated cell which contains the crystal with platinum-plated electrodes. The frequency change is proportional to the silver concentration in the range 10^?6?3 × 10^?5 M after electrodeposition for 10 min, and 2 × 10^?7?1 × 10^?6 M for 1 h.     

A simple dual-channel sensor for detecting cyanide in water with high selectivity and sensitivity

Taking advantage of the special nucleophilicity of cyanide, a new simple colorimetric chemosensor has been synthesised. This allows a deprotonation reaction to monitoring the cyanide. With the addition of CN^? to the chemosensor aqueous solution, which could induce a change in the solution colour from yellowish to deep yellow, while no colour change could be observed in the presence of other hackneyed anions, by which CN^? can be distinguished from other anions immediate with the naked eye. At the same time, a fluorescence quenching was implemented upon adding cyanide into the chemosensor aqueous solution. The absorption spectra detection limits of the chemosensor for cyanide was 5.35 × 10^?8 M and the fluorescence spectra detection limit was 2.63 × 10^?8 M. The cyanide test strips based on the chemosensor could serve as a convenient cyanide test kits. Furthermore, the chemosensor was successfully applied to detect cyanide in sprouting potatoes.     

二钼酸铵晶体饱和水溶液Raman光谱的变异现象及其机理

记录了常温下二钼酸铵晶体饱和水溶液的Raman光谱，并分别与二钼酸铵晶体、仲钼酸铵晶体、仲钼酸铵晶体饱和水溶液、水溶液状态下单钼酸根离子的Raman光谱进行了比较研究。结果表明：二钼酸铵晶体饱和水溶液Raman光谱相对二钼酸铵晶体Raman光谱，明显地发生了变异现象。二钼酸铵晶体饱和水溶液Raman光谱其主要特征峰最高振动频率937.6 cm^-1与仲钼酸铵晶体饱和水溶液Raman光谱主要特征峰最高振动频率937.6 cm^-1完全吻合，而其次高振动频率893.9 cm^-1，恰好介于水溶液中单钼酸根离子Raman光谱主要特征峰最高振动频率895.1 cm^-1与仲钼酸铵晶体饱和水溶液Raman光谱主要特征次高峰振动频率891.0 cm^-1之间，而且三者彼此接近。二钼酸铵晶体饱和水溶液Raman光谱主、次特征峰强度之比值为2.1，与仲钼酸铵晶体饱和水溶液Raman光谱主、次特征峰强度之比值4.4相比，一半不足。提出了一种利用Raman光谱主要特征峰振动频率及其主、次特征峰强度之比值对二钼酸铵晶体饱和水溶液组分同时进行定性和半定量分析的新方法。发现了常温下二钼酸铵晶体饱和水溶液中二钼酸根离子Mo₂O₇^2-已经不复存在，完全转变成了优势组分仲钼酸根离子Mo₇O₂₄^6-和次要组分单钼酸根离子MoO₄^2-；证明了常温下含钼水溶液酸化过程中溶液Raman光谱离散性变化现象的存在。运用结构化学和物理化学原理同时讨论了二钼酸铵晶体饱和水溶液Raman光谱发生变异现象的机理。     

Pneumatopotentiometric determination of nanogram amounts of cyanide

Hydrogen cyanide is liberated from aqueous samples by reaction with sulphuric acid and transferred by a stream of nitrogen to a silver porous membrane electrode. Some HCN passes through the membrane into an alkaline dicyanoargentate solution; the cyanide ion produced causes a decrease in the equilibrium Ag⁺ concentration and the change of potential is related to the amount of cyanide in the sample. The detection limit is 3.0 ng ml^?1 cyanide in the injected solution; the relative standard deviation is 0.82% for 17 ng of cyanide. Sulphide interferes (as H₂S) but can be removed on a lead acetate column.     

A gold nanoparticle-based colorimetric sensing ensemble for the colorimetric detection of cyanide ions in aqueous solution

A colorimetric sensing ensemble was prepared by mixing readily prepared adenosine triphosphate (ATP)-stabilized AuNPs with Cu²⁺-phenanthroline complexes. The sensing mechanism of the ensemble was examined by UV-vis spectrometry and transmission electron microscopy. The studies showed that the Cu²⁺-phenanthroline complex was converted to free phenanthroline when exposed to cyanide anions and the free phenanthroline caused the ATP-stabilized AuNPs to aggregate, which in turn, resulted in a visible color change in the AuNP solution. The ensemble could detect cyanide ions in aqueous solution at physiological pH, either spectrophotometrically or visually, with high selectivity toward cyanide anions over a range of mono- and di-anions commonly found in biological and environmental systems. This sensing ensemble also allows a quantitative assay of the analyte in a neutral aqueous solution, down to a concentration of 10⁻⁵ M.     

Selective colorimetric assay of cyanide ions using a thioamide-based probe containing phenol and pyridyl groups

The selective assay of cyanide ions with a thioamide compound (HNPTU) containing phenol and pyridine as a chemosensor is reported using absorbance changes in a buffered aqueous solution (50 mM HEPES, pH 7.4) containing ethanol. Upon treatment with cyanide ions, the colorless solution of HNPTU turned yellow. No significant changes were observed with other comparable anions, such as F⁻, Cl⁻, Br⁻, I⁻, and CH₃COO⁻. The color change of HNPTU upon treatment with CN⁻ was maintained even in the presence of the comparable monovalent anions. The complex stability constant (K_a = 2.6 × 10³) for the stoichiometric 1:1 complexation of HNPTU with cyanide ions was obtained based on absorbance titrations. The interaction of HNPTU with cyanide ions was proposed to be deprotonation, as shown by NMR and Cu(II) treatment experiments.     

The adaptation of coated piezoelectric devices for use in the detection of gases in aqueous solutions

A method for the determination of ammonia and hydrogen sulfide in aqueous solution is presented. This method involves the use of a gas-permeable membrane which isolates the piezoelectric crystal device from the solution yet allows the desired gases to pass. Concentrations up to 0.45 M for NH₃, and 9 · 10^-4 M for H₂S give linear calibration curves of concentration vs. frequency change.     

Effect of metal ions on a piezoelectric quartz crystal in aqueous solution and the adsorptive determination of iron(III) as phosphate

At 1.5 V applied between the electrodes on the piezoelectric crystal, many metals electrodeposit on an electrode so that the frequency changes. Iron(III) (1 × 10^?5-1 × 10^?4 M) can be determined by adsorption of iron(III) phosphate which also causes a frequency change. Electrodeposition can be prevented by covering one electrode with a thin glass plate.     

咪唑-氰基合铁(Ⅲ)氢键型超分子晶体的合成、相变及介电性质

通过溶剂蒸发法,咪唑、18-冠醚-6和铁氰酸在甲醇溶液内反应,获得了氰基合铁配合物氢键型笼状超分子晶体材料(C3H5N2)3[Fe(CN)6]·2(18-crown-6)·2H2O(1)。通过变温X射线单晶衍射、红外光谱、元素分析、热重分析(TG)、差示扫描量热法(DSC)和变温-介电常数测试等对该晶体进行了结构、热能及电性能分析。该晶体的空间群为P21/c,属于单斜晶系,结构显示氰基合铁阳离子、水分子和咪唑阳离子在空间内通过氢键的相互作用形成以铁原子为顶点的三维笼状结构。温度变化触发笼状结构突变,同时引起[Fe(CN)6]3-框架内超分子发生动态摆动,从而引起晶体结构发生相变,该结构相变温度区间伴随介电物理特性阶梯状变化,从220到280 K,介电常数由38变为43,且可逆。温度在270 K之后的介电突然跃升是水汽影响导致。     

Mercury(II) cyanide complexes of thioureas and the crystal structure of [(N-methylthiourea)2 Hg(CN)2]

Mercury(II) cyanide complexes of thioureas (Tu), N-methylthiourea (MeTu), and N,N′-dimethylthiourea (DmTu)) have been prepared and characterized by IR and NMR (¹H and ¹³C) spectroscopy, and the crystal structure of one of them was determined by X-ray crystallography. An upfield shift in ¹³C NMR and downfield shifts in ¹H NMR are consistent with the sulfur coordination to mercury(II). The appearance of a band around 2200 cm^?1 in IR and a resonance around 145 ppm in ¹³C NMR indicates the binding of cyanide to mercury(II). The NMR data show that the [(Thione)₂Hg(CN)₂] complexes are stable in solution and undergo no redistribution reactions. In the crystal structure of the title complex, mercury atom is coordinated to two thione sulfur atoms of MeTu and to two cyanide carbon atoms in a distorted tetrahedral mode with the bond angles in the range of 90.2(2)°–169.3(3)°.     

Determination of picomolar concentrations of bromide with a piezoelectric detector by catalysis of the permanganate/iodide reaction

The piezoelectric quartz crystal has been utilized to detect iodine produced by the bromide- catalyzed oxidation of iodine to iodate by permanganate in acidic solution. After extraction of iodine into toluene, the resulting frequency change caused by iodine adsorption on the crystal electrode is proportional to bromide concentration over the range 0.5–5 × 10^?12 M. Only silver (I), mercury(II) and large concentrations of chloride interfere significantly. The crystal detector is also used to indicate the end-point of a chloride titration with silver.     

Absorption properties of commercial lead chromates

For the cyanide determination in waste waters containing more than 2.5×10^?6 Mol of CN^?/l a conductometric method has been proposed. The sulphuric acid containing samples were distilled and the obtained HCN was passed into a 5×10^?4 Mol/l AgNO₃ solution, of which the conductivity was measured. The method offers the possibility of a precise observation of the completion of the HCN distillation and also the direct measurement of the cyanide concentration by the change of conductivity. The analysis time is about 40 min.     

Design and Performance of a New Thin‐Layer Radial‐Flow Holder for a Quartz Crystal Resonator of an Electrochemical Quartz Crystal Microbalance

A new compact holder for either 5‐ or 10‐MHz AT‐cut quartz crystal resonator of an electrochemical quartz crystal microbalance was designed, fabricated and characterized. The holder is a hydrodynamically controlled thin‐layer radial‐flow microelectrochemical cell. Its unique feature consists of (i) a micrometer‐screw adjustable distance between the movable coaxial assembly of the Ag/Ag⁺ pseudoreference electrode and the inlet capillary nozzle with respect to the metal‐film working electrode of the quartz crystal resonator, and (ii) a U‐clamp mountable resonator, easily accessible for change without using any tools. The inlet solution stream is centered axially against the working electrode. The holder performance was tested under different flow conditions. These include hydrodynamic voltammetry measurements on the Fe(CN) /Fe(CN) couple, i.e., a redox system with no mass transfer across the solution–electrode interface, as well as simultaneous chronoamperometry and chronoelectrogravimetry measurements under flow injection analysis (FIA) conditions on the Ag/Ag⁺ couple, i.e., a system with electrodeposition of a rigid metallic film. Moreover, simultaneous changes of resonant frequency and dynamic resistance were measured under FIA conditions for a glycerol solution, i.e., an electroinactive viscous medium. For the 30<F_m<180 μL min^?1 volume flow rate of solution and 50<d<250 μm nozzle‐to‐resonator distance, the holder operates in a thin‐layer radial‐flow regime at a fully developed laminar flow. For F_m=30 μL min^?1 and d=100 μm, both mass and charge conversion accompanying silver electrodeposition is appreciably high and close to 35%. Simultaneous measurements of the resonant frequency change and current‐potential or current‐time transients allowed investigations of electrochemical processes involving mass changes of rigid deposits while those of the frequency change and dynamic resistance change involve changes of viscoelastic properties of medium.     

Spectral properties and analytical application of the ternary complex of lanthanum(III) with 1,10-phenanthroline and eosin

The pink lanthanum—(1,10-phenanthroline)₂—(eosin)₂ complex is used to determine 0.5–10 × 10^-5 M lanthanum, either in aqueous solution or chloroform. In the presence of EDTA, only aluminium and cyanide interfere.     

Selective determination of silver in solution by adsorption on a piezoelectric quartz crystal

Electrodeposition of metal ions on the crystal is eliminated by using a specially constructed transistorized oscillator. When tartrate, citrate, EDTA or their mixtures are present, silver adsorption occurs. The frequency change is proportional to the silver concentration in the range 2 × 10^?7?1 × 10^?5 M after adsorption for 10 min from a 1 mM EDTA/3 mM tartrate solution. No significant interferences are caused by other metal ions. On the basis of cyclic voltammetric studies, it is suggested that silver is adsorbed as a silver (I) complex.     

A New Spectrophotometry Determination of Cyanide by Solvent Extraction as Tris-(1,10-Phenanthroline)-Iron (II)-Thiocymate

Abstract

By shaking aqueous cyanide solution with nitrobenzene contained sulfur, thiocyanate is formed and is extracted into the nitrobenzene as an ion pair of thiocyanate anion and tris-(1,10-phenanthroline)-iron(II) chelate cation. By measuring the color intensity of the organic phase at 516 nm, cyanide is determined spectrophotometrically. A linear calibration curve is obtained up to 4 × 10^?5M of cyanide in the aqueous phase.     

A simple Schiff base as ‘naked eye’ and fluorescent ‘on–off’ sensor for detecting cyanide in mixed aqueous solution

A simple Schiff base sensor (L₁) derived from N-(1-naphthyl) ethylenediamine dihydrochloride was designed and synthesised by simple chemistry procedures. The sensor exhibited a visible colour change observed by both colorimetric and fluorimetric responses for cyanide ion in aqueous solution. The detection of cyanide was performed via the nucleophilic attack of cyanide anion on the imine group of the sensor with a 1?:?1 binding stoichiometry. Moreover, test strips based on the sensor were fabricated, which served as convenient and efficient CN^? test kits and the sensor L₁ is a good way to detect hydrogen cyanide in aqueous extracts of sprouting potatoes.