Polarographic determination of cyanide as contaminant in pralidoxime mesylate formulations

A method for the polarographic determination of cyanide as contaminant in pralidoxime mesylate (PM) formulations was developed. The volatile cyanide formed in the formulations was stabilized as tetracyanonickelate (TCN) anion complex after reaction with ammoniacal Ni(II) solution. The stable TCN anion complex (K(stb)=10(31)) was determined by anodic stripping voltammetry at the hanging mercury drop electrode (HMDE). The polarographic signal was proportional to the cyanide concentration and the high concentration of PM did not interfere. The linear range of calibration was from 1.2 to 16 mug cyanide with r=0.998. The RSD was 1.3% (n=5) for 2.4 mug cyanide and a detection limit of 0.8 mug cyanide was calculated. The proposed method is adequate as a quality control of PM formulations.     

Determination of cyanide in microsamples by means of capillary flow injection analysis with amperometric detection

A new approach for determining cyanide in microsamples is described. The method is based on capillary flow injection analysis (CFIA) with amperometric detection. The sensing electrode is a silver-plated microdisk electrode, where cyanide can react under formation of a dicyanoargentate complex. A remarkably low mass detection limit of 231 fmol cyanide is obtained for an injection volume of 60 nl. The sample throughput of the CFIA-arrangement is comparable with a conventional sized FIA-system. A practical application is given by analyzing the cyanide (amygdalin) concentration in apple kernels.     

Amperometric method for on-line cyanide detection

An amperometric method for the detection of cyanide has been developed based on the anodic dissolution of gold in solutions containing cyanide. The method is characterized by a cyclic regeneration of the electrode surface. During the regeneration, the surface layers on the electrode are dissolved. By selection of suitable measuring potentials for the cyanide, linearity can be shown to exist between current and cyanide concentration over the concentration ranges from 0 to 10 mg/l and 10 to 100 mg/l. The lowest detection level is about 0.05 mg CN^–/l. Determinations in the concentration range investigated are possible at a measuring potential of E=270 mV. The method is suitable for detecting the end point during the decontamination of cyanide-containing sewage. The influence on the results of pH, temperature, flow rate, heavy metal content, type of decontamination agent and the presence of brighteners is discussed.     

Pheumatoamperometric determination of cyanide,sulfide and their mixtures

A rapid pneumatoamperometric method for quantifying cyanide in the presence or absence of sulfide is described. The gaseous mixture of hydrogen cyanide and hydrogen sulfide is separated by inserting a short chromatographic column packed with silica gel between the reaction vessel used to generate the volatile acids and the porous gold electrode that the detects them. The detection limit is ca. 5 ng cyanide in 2 ml of solution regardless of sulfide content. The detection limit for sulfide is ca. 1.0 ng in 2 ml of solution when cyanide is present and ca. 0.7 ng in absence of cyanide. Both sulfite and nitrite interfere.     

Determination of cyanide using a microbial sensor

A microbial cyanide sensor was prepared, consisting of immobilizedSaccharomyces cerevisiae and an oxygen electrode. When the electrode was inserted into a solution containing glucose, the respiration activity of the microorganisms increased. The change in the respiration activity is monitored with the oxygen electrode. When cyanide is added to the sample solution, the electron transport chain reaction of the respiration system in the mitochondria is inhibited, resulting in a decrease in respiration. The inhibition is caused by cyanide binding with respiration enzymes such as the cytochrome oxidase complex in the mitochondrial inner membrane. Therefore, the cyanide concentration can be measured from the change in the respiration rate. When the sensor was applied to a batch system at pH 8.0 and 30°C, the cyanide calibration curve showed linearity in the concentration range between 0.3 μM and 150 μM CN-.     

Gas-diffusion separation and flow injection potentiometry

Summary The similarities and differences of the operation principle of gas-sensing electrodes and potentiometric detection coupled to gas-diffusion separation in flow injection analysis are discussed with special emphasis on selectivity and sensitivity aspects. Several examples of application are presented highlighting the improvements in detectability obtained by gas-diffusion flow injection potentiometry. High sensitivity determination of ammonium is achieved through accumulation of ammonia released from the sample stream in the small recipient volume of the gas-diffusion unit. A method for almost specific determination of cyanide is presented making use of gas-diffusion separation of hydrogen cyanide and potentiometric detection with a selective AgI membrane electrode. The interference of sulfide is totally prevented by its oxidation in the donor line. If applied to potentiometric measurement following gas diffusion separation an intrinsically non-selective metallic silver wire electrode turns out to enable the selective detection of sulfide with high sensitivity and fast response. A new approach for diffusive sampling and on-line detection of gas-phase contaminants is exemplified by the determination of NO_x.     

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.     

Voltametrische Titration von Cyanid mit Quecksilber(II)-chlorid und ihre Anwendung zur Cyanidbestimmung in Wasser und Abwasser

Zusammenfassung Es wird ein Verfahren zur Titration von Cyanid mit Quecksilber(II)-chlorid beschrieben. Die Endpunktsbestimmung erfolgt voltametrisch unter Verwendung einer rotierenden Palladiumindicator- und einer Kalomelbezugselektrode. Die Methode ist im Bereich zwischen 40 ppb und 200 ppm anwendbar und wird vorzugsweise zur Cyanidbestimmung in Kamingasen, Wasser und Abwasser eingesetzt.

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Voltametric titration of cyanide with mercuric chloride and application to the determination of cyanide in water and waste water

A method is described for the volumetric determination of cyanide with mercuric chloride solution. The end-point detection is carried out voltametrically using a polarized rotating palladium electrode and a calomel reference electrode. The method covers a concentration range of between 40 ppb and 200 ppm cyanide and is in particular suitable for cyanide determinations in stack gases, water and waste water.

     

On-line determination of cyanide in the presence of sulfide by flow injection with pervaporation

A pervaporation-flow injection (PFI) method is described for the analysis of cyanide in the presence of sulfide. The interfering sulfide ion in the injected sample is precipitated on-line using an acidified lead nitrate reagent solution before the donor stream enters the pervaporation cell. Using amperometric detection at a silver electrode set at −50 mV (vs Ag/AgCl), linear calibration was obtained in the range 0.02–100.0 mg l⁻¹ with a detection limit of 1.0 μg l⁻¹. Sample throughput was of the order of 12–15 h⁻¹. When the method was applied to the analysis of synthetic samples, there was no significant interference from sulfide at concentrations up to 50 mg l⁻¹. Thiocyanate did not interfere at levels up to 1000 mg l⁻¹. When applied to industrial samples containing sulfide and thiocyanate ions where the cyanide ions are predominantly complexed with various metal ions the PFI method was found to give results close to those obtained by standard distillation methods for weak acid dissociable (WAD) cyanide.     

Liquid-membrane dicyanoargentate-sensitive electrodes based on quaternary ammonium salts

Several quaternary ammonium salts have been synthesized and comparisons made of their efficiency as exchange substrates in dicyanoargentate-sensitive electrodes. The electrode prepared from hexadecyltrioctylammonium dicyanoargentate shows the best performance characteristics and has been studied in more detail. Its Nernstian response range is 10(-1)-10(-4)M, the optimum pH range is 10.6-12.6, and the detection limit is 3 x 10(-5)M. It is suggested that the detection limit of the electrode is controlled by interference from cyanide ions, and the difference between detection limits obtained with the various electrodes is discussed in the light of this. Selectivity coefficients for various interfering ions have been determined and related to the extractability of the ions. The electrode has been applied to determination of silver in cyanide-containing plating solutions.     

Ion chromatographic determination of sulfide and cyanide in real matrices by using pulsed amperometric detection on a silver electrode

The determination of free sulfide and cyanide by pulsed amperometric detection (PAD) at a silver-working electrode was improved through a deep de-oxygenation (at least 10 min) of both standard and real solutions containing the two analytes and adopting a two-potential waveform able to eliminate Ag working electrode fouling. The waveform stepped around the oxidation of Ag in the presence of 0.1-0.4 M hydroxyl ion, from -0.1 to 0.1 V versus saturated calomel electrode (SCE). The eluent composition (0.4 M NaOH plus 7.5 mM oxalate solution) allowed a very good column efficiency and selectivity. The presence of a polysulfide species was hypothesized in sulfide solutions that had not been de-oxygenated and aged. The polysulfide eluted just before sulfide and was confirmed by a chemical test with SO3(2-) producing the elimination of the polysulfide peak. Detection limits, according to the Hubaux-Vos method, were 1.0 and 2.0 microg/l for S2- and CN , respectively. We demonstrated good performance of the optimized method by repeatedly injecting standard solutions and by analyzing different real matrices. The method exhibited very good accuracy and repeatability (10 microg/l and a 500 microl injection loop, had a repeatability better than 3% for sulfide and 100 microg/l had a repeatability better than 1% for cyanide). The two-potential waveform ensured long-term stability of the electrode surface that required no manual polishing procedure for at least 1 month (20 analysis per day).     

乙腈溶液中银电极的表面增强拉曼光谱研究

利用共焦显微拉曼系统研究了非水体系0.1mol·L^-1LiClO4/CH3CN溶液中,乙腈分子在粗糙银和金电极表面的吸附和解离行为。结果表明非水体系中乙腈可在银、金表面发生还原反应,产物CN^-离子与电极表面作用形成的表面配合物可以较宽的电位区间吸附于电极表面。溶液中的微量水、激光照射以及电极电位均对该反应有较大的影响。通过拉曼谱图的比较,得出乙腈分子解离出的CN^-在金电极表面比在银电极表面有更强的吸附作用。     

Continuous Determination of Free Cyanide by Means of Membrane Diffusion of Gaseous HCN and An Electrode Indicator Technique

Abstract

A continuous measurement system for free cyanide has been developed based on the principle of diffusion across a gas-permeable membrane to affect the separation of hydrogen cyanide from the acidified sample solution. The cyanide absorbed in the alkaline indicator solution is subsequently analyzed by an indirect technique using a silver ion-selective electrode. In the concentration range of 30 to 400 μg CN^?/L, the accuracy and precision of this method is approximately two percent. The detection limit of this system is approximately 0.5 μg CN^?/L.     

An Efficient Probe for Rapid Detection of Cyanide in Water at Parts per Billion Levels and Naked‐Eye Detection of Endogenous Cyanide

A new molecular probe based on an oxidized bis‐indolyl skeleton has been developed for rapid and sensitive visual detection of cyanide ions in water and also for the detection of endogenously bound cyanide. The probe allows the “naked‐eye” detection of cyanide ions in water with a visual color change from red to yellow (Δλ_max=80 nm) with the immediate addition of the probe. It shows high selectivity towards the cyanide ion without any interference from other anions. The detection of cyanide by the probe is ratiometric, thus making the detection quantitative. A Michael‐type addition reaction of the probe with the cyanide ion takes place during this chemodosimetric process. In water, the detection limit was found to be at the parts per million level, which improved drastically when a neutral micellar medium was employed, and it showed a parts‐per‐billion‐level detection, which is even 25‐fold lower than the permitted limits of cyanide in water. The probe could also efficiently detect the endogenously bound cyanide in cassava (a staple food) with a clear visual color change without requiring any sample pretreatment and/or any special reaction conditions such as pH or temperature. Thus the probe could serve as a practical naked‐eye probe for “in‐field” experiments without requiring any sophisticated instruments.     

Oxidation of the cyanide ion at a platinum electrode studied by polarization modulation infrared reflection absorption spectroscopy

The anodic oxidation of the cyanide ion at a platinum electrode in aqueous solution was observed by polarization modulation infrared reflection absorption spectroscopy(PM IRRAS). The cyanide ion was adsorbed on the electrode surface in the potential region more negative than 0.4 V (versus Ag/AgCl). In the more positive region (> 0.4 V ), the adsorbed cyanide ion was oxidized to form the cyanate ion. Cyanogen was not detected during the oxidation reactions; this suggests direct electrochemical formation of the cyanate ion.     

Catalase biosensor for the determination of hydrogen peroxide,fluoride and cyanide

The enzyme catalase, which catalyses the decomposition of hydrogen peroxide to oxygen and water, was immobilized in a membrane by entrapping it in polyacryl amide and contacted to a Clark-type oxygen electrode. With the resulting catalase biosensor it was possible to detect the substrate hydrogen peroxide and the inhibitors fluoride and cyanide in phosphate buffer.The sensor was integrated into a flow system. In the concentration range from 5–200 mg/l a linear dependence of the peak height on the hydrogen peroxide concentration was obtained. The average decrease in activity during 30 days of storage at 6 °C was 17%. Fluoride and cyanide could be determined by measuring the inhibition of the enzymatic reaction in the same flow system. The analysis was executed in three steps; namely determination of the original activity by pumping substrate solution, inhibition of the enzyme by pumping inhibitor solution, and determination of the activity after the inhibition.The decrease in activity correlated with the inhibitor concentration of the sample, but a linear dependence was not found. The inhibition of fluoride and cyanide was both reversible, the enzyme membrane could be reactivated completely by pumping substrate solution. The detection limit was 1 mg/l for fluoride and 1.5 mg/l for cyanide.     

碱性介质中甘氨酸在Pt电极上解离吸附和氧化反应的原位红外反射光谱研究

运用原位红外反射光谱研究了碱性介质中甘氨酸在Pt电极上的解离吸附和氧化反应行为,并利用纳米Pt膜电极的异常红外效应鉴定反应过程中生成的表面吸附物种.结果表明:甘氨酸在Pt电极上极易发生解离,生成强吸附于电极表面上的氰基负离子,该吸附物种在低于0V电位下能稳定存在,并抑制甘氨酸的进一步反应.当电位高于0.2V时,氰基负离子被氧化为氰酸根离子进入溶液,使甘氨酸发生氧化反应,生成氰酸盐和碳酸盐等产物.     

Improved gas chromatography with electron-capture detection using a reaction pre-column for the determination of blood cyanide: a higher content in the left ventricle of fire victims

We developed a head-space method for the determination of blood cyanide by gas chromatography with electron-capture detection. In this technique, a reaction pre-column, packed with chloramine-T, was used for the conversion of hydrogen cyanide into cyanogen chloride. Since the reaction pre-column eliminated the necessity for trapping hydrogen cyanide from the biological samples, blood cyanide was quickly analysed by acidification only. The reaction pre-column was durable for at least several months. The calibration curve gave good linearity when dichloromethane was used as the internal standard, and the lower detection limit taken from this plot was ca. 0.05 micrograms/ml. The relative standard deviation of spiked blood samples was in the range 0.6-3.9%. We determined blood cyanide levels at autopsy in victims who had died from fire using this method. A significantly higher cyanide content was detected in the left ventricular blood than in the right. There was a positive correlation between blood cyanide and carboxylhaemoglobin contents. This simple and sensitive technique could be very useful for the determination of cyanide in various samples.     

A selective modified carbon paste electrode for determination of cyanide using tetra-3,4-pyridinoporphyrazinatocobalt(II)

A chemically modified carbon paste electrode with 3,4-tetra pyridinoporphirazinatocobalt(II) (Co(3,4 tppa) was applied to the determination of free cyanide ion. The electrode has a linear range between 1.5 × 10⁻⁵ M and 1.0 × 10⁻² M with a Nernstian slope of 60 ± 1.5 mV/decade and its detection limit is 9 × 10⁻⁶ M. The response time of electrode is 5 min. The proposed electrode was applied successfully for the determination of cyanide in commercially available spring water. Some anions, such as SCN⁻, I⁻, Cl⁻, Br⁻ and oxalate that are usually serious interfering species for most of cyanide selective electrodes, did not have any interfering effect for this proposed electrode.     

Determination of low levels of cyanide with a silver/silver sulphide wire electrode

A silver/silver sulphide electrode is prepred quickly by holding a cleaned silver wire in vapours from molten sulphur. In 1000–10 mg l^?1 cyanide solutions, the electrode exhibits a linear E/log C_CN function which becomes slightly sinusoidal for 10–0.1 mg l^–1 cyanide. The average slope is slightl super-Nerstian (10 mV/decade concentration). The applicability of the electrode is demonstrated for the determinations of microgram quantities of water-soluble cyanide from the Prussian blue pigments which are constituents of externally applied cosmetics. The home-made electrode provides results agreing with those obtained with commercially available electrodes.