Spectrophotometric determination of cyanide ions through ligand exchange reaction in solution

Summary A simple spectrophotometric method for the determination of trace amounts of cyanide ions in aqueous medium, using a heterocyclic azo dye complexed with mercury(II) for the first time, is described. The visual comparative method has been used in which a stronger complexing anion displaces a coloured reagent from the metal-ligand complex. Ammonium (2-amino-3-hydroxy-pyridyl-4 azo)benzene-4-arsonate (AHP-4A) complexed with mercury(II) has been used for the determination of 0.13–1.46g/ml of cyanide ions with fair accuracy. The anion has also been determined, when cyanide ion reacts with mercury(II)-(AHP-4A) complex, probably forming a bridged complex. The increase in absorbance is proportional to the cyanide ion concentration in the range of 0.04–0.37g/ml, but this method is not very precise. The effect of foreign ions has also been studied. The sensitivities of other mercury(II) complexes in the determination of cyanide ions have been compared.

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Zusammenfassung Eine spektrophotometrische Methode zur Bestimmung von Spuren Cyanid in wäßrigem Milieu mit Hilfe eines mit Hg(II) komplexierten heterocyklischen Azofarbstoffes wurde beschrieben. Hierbei verdrängt ein stärker komplexierendes Anion das Farbreagens aus dem Metallkomplex. Ammonium(2-amino-3-hydroxypyridyl-4-azo)benzol-4-arsenat (AHP-4A) in komplexer Verbindung mit Hg(II) wurde für die genaue Bestimmung von 0,13–1,46g CN^–/ml verwendet. Das Anion wurde auch nach der Reaktion von Cyanid mit Hg(II)-(AHP-4A)-Komplex (wahrscheinlich zu einer Brückenverbindung) bestimmt. Der Anstieg der Extinktion ist der Cyanidkonzentration im Gebiet 0,04–0,37g/ml proportional, aber dieses Verfahren ist nicht sehr genau. Der Einfluß von Fremdionen wurde untersucht. Die Empfindlichkeit anderer Hg(II)-Komplexe wurde zum Vergleich herangezogen.

     

Spectrophotometric phosphate determination in urine by ligand exchange extraction

A new spectrophotometric method for the determination of phosphate in urine is proposed, based on the ligand exchange extraction produced by phosphate solution at pH 7.5 when it is shaken with a solution of Fe(III) indole-2-carboxylate iniso-amyl alcohol. The organic layer decoloration is measured at 400 nm and the phosphate indirectly determined. The sensitivity of the method is 1.07 × 10³ 1 mol^–1 cm^–1, the linear working range 1–15 × 10^–5 mol/l of phosphate and the relative standard deviation 5%. It does not require previous treatment of the sample and it is free from interferences by other normal or pathological constituents of the urine samples. The results agreed closely with those obtained by using a Sigma Diagnostics procedure for inorganic phosphorus, based on the Fiske-SubbaRow method. The method does not require special instrumentation and is not expensive.     

Kinetics and mechanism of the reaction between thiosulfate and chlorite ions at 90°C

The kinetics of the oxidation of S₂O₃^2? by ClO₂^? have been studied in aqueous alkaline solution at 90⁰C using classical titrimetric methods to follow the course of the reaction. The reaction takes place according to the stoichiometry S₂O₃^2? + 2ClO₂^? + 2OH^? = 2SO₄^2? + 2Cl^? + H₂O even in large S₂O₃^2? excess. There is some indication of a complex reaction pattern, but 70% of the ClO₂^? disappearance can be best described by the autocatalytic rate equation -d[ClO₂^?]/dt = k[S₂O₃^2?] [ClO₂^?] [H⁺] with k = (1.3 ± 0.2) ×10⁸ M^?2 sec^?1. The mechanism is explained by postulating nucleophilic attack of S₂O₃^2? on HClO₂ to form a chlorine-containing intermediate.     

Spectrophotometric determination of aluminum and copper ions using spadns

Aluminum and copper ions are selectively estimated spectrophotometrically. These ions form colored complexes with spadns which have a maximum absorbance at 580 nm. The complexes formed with both cations are stable and pH dependant; aluminum is favorably complexed at pH 5, while copper is complexed at pH 7.The percentage recoveries were found to be 99.69 ± 0.75 and 99.32 ± 0.6 with a minimum detection limit of 0.08 and 0.23 g ml^–1 for aluminum and copper ions respectively. There is insignificant interference from the 10-fold concentrations of other metal ions under the proposed reaction conditions.     

Coordination and ligand exchange dynamics of solvated metal ions

Recent developments in computer speed and capacity have opened the access to highly accurate molecular dynamics simulations based on quantum mechanically calculated forces for the chemically relevant region around ions in solution (QM/MM formalism). This accuracy, although still extremely consuming (30-300 days of CP time per simulation), is needed for reliable structural details and ligand exchange rates. A large number of main group and transition metal ions have been investigated by this approach, giving very detailed insight into the properties of these ions in solution and allowing to classify the ions by various characteristics. Most first-row transition metal ions have a very stable first hexa-coordinated solvation shell, whose vibrational distortions, however, strongly influence the dynamics of the second shell. The dynamical Jahn-Teller effect - shown to be a femto- and picosecond phenomenon - can strongly influence ligand coordination and exchange dynamics. A large number of ions with very labile solvation shell such as most main group ions, but also transition metal ions, e.g. Ag(I) and Hg(II), can change their coordination within the picosecond scale, leading to an almost simultaneous presence of several species hardly accessible by present experimental techniques. Among these ions, the structure breakers are of particular interest, and it could be shown that there are two types of them, one with a large and very labile first coordination shell such as Cs(I), the other characterised by a small first but an unusually large second solvation shell such as Au(I). Investigations of metal ions coordinated to ammonia ligands have shown that coordination to hetero-atoms can accelerate the ligand exchange reaction rates by several orders of magnitude, e.g. for Cu(II) and Ni(II). Simulations of ions in aqueous ammonia gave a very detailed picture of the complexity of species almost simultaneously present and illustrate the enormous difficulties encountered when trying to fit X-ray or neutron diffraction data for such systems. In general, ligand exchange rates situated in the picosecond range are far below the NMR scale, and as femtosecond laser pulse spectroscopy could not be applied so far to ionic solutions, accurate simulations have become a very important tool to access structure and dynamics of solvated ions. A number of VIDEO clips supplied on the Web as supporting material illustrates the processes occurring in solutions of the metal ions.     

Spectrophotometric determination of some phenolic sympathomimetic drugs through reaction with 2,6-dihaloquinone chlorimides

A spectrophotometric procedure is described for the determination of three phenolic sympathomimetic drugs: etilefrine hydrochloride, prenalterol hydrochloride and ritodrine hydrochloride. The method involves the use of 2,6-dichloro- and 2,6-dibromoquinone chlorimides as chromogenic reagents. The phenolic drugs produce a blue color, peaking from 610 to 630 nm. The colors produced obey Beer's law and are suitable for the quantitative determination of the named compounds. The molar ratios of the reactions were established and a proposal for the reaction pathway is given. The procedures described were applied successfully to the determination of the compounds in their dosage forms. The results showed that the proposed procedures compared favourably with the reference methods and satisfactory sensitivity, accuracy and precision (SD < 0.1 g ml^–1) were noted. Detection limits are typically 0.2–0.4 g ml^–1. Other advantages of the procedures are their simplicity and speed.     

Spectrophotometric determination of thiocyanate ions in stratal waters

The formation of [FeSCN]²⁺ complex in hydrochloric and sulfuric acid medium was studied by spectrophotometry using iron(III) sulfate and ammonium iron(III) sulfate solutions as reactants. A method for the determination of 10–200 μg SCN^? in 25 mL water solutions containing ammonium iron(III) sulfate in sulfuric acid medium was developed; its determination limit is 2.6 μg (P = 0.99, n = 9). The method was applied for the analysis of model water samples with macro- and micro-component compositions similar to that of water from the Arigol licensed area. Operational control of the accuracy rate was performed by the standard addition method. The developed method can be applied to analyze water samples containing 1–90 mg/L thiocyanate ions.     

氧化苯胺蓝褪色光度法测微量锰

研究了在H2SO4介质中,锰(VII)能氧化苯胺蓝使其褪色,且褪色的程度随锰量变化呈线性关系,据此建立了测定锰的光度分析方法。实验测定波长为602nm,表观摩尔吸光系数为 2.72?104 L?mol-1?cm-1,锰的量在0 ~100?g/25mL范围内服从朗伯-比尔定律,茶叶中常见金属元素不干扰测定,方法在用于测定茶叶中微量锰时,其相对标准偏差在1.7%～2.9%之间,回收率为100.8%～103.2%     

Spectrophotometric determination of titanium after separation by anion exchange

A method is outlined for separation of titanium by anion exchange and subsequent spectrophotometric determination. Titanium fluoride is adsorbed quantitatively on a column of strongly basic anion exchanger and thus separated from ions which would normally interfere. The spectrophotometric measurement is achieved by formation of the intensely yellow and stable titanium ascorbate complex which has a maximum absorbance at 355 mμ.     

双硫腙褪色光度法测定痕量铈

研究了Ce(Ⅳ)在H2SO4介质中和溴化十六烷基吡啶存在下催化H2O2氧化双硫腙的褪色反应及其动力学条件,测定了反应级数和表观活化能,建立了测定痕量铈的新方法。双硫腙的最大吸收波长为450nm,该方法的检出限为1 9×10-9g/mLCe(Ⅳ),线性范围为0～150ng/mLCe(Ⅳ),方法可用于人发中痕量铈的测定。     

Spectrophotometric determination of anilines based on charge-transfer reaction

The molecular interactions between aniline, p-toluidines, benzidine and p-phenylenediamine as electron donors and 7,7,8,8-tetracyanoquinodimethane (TCNQ) as acceptor have been investigated by spectrophotometric method. Different variables affecting the reaction were studies and optimized. At the optimum reaction conditions Beer's law was obeyed in a concentration limit of 0.6-3.0, 0.3-3.0, 0.3-3.0 and 0.3-2.7 microg ml(-1) for aniline, p-toluidines, benzidine and p-phenylenediamine. The developed methods were applied successfully for the determination of the studied compounds in waste water and relative standard deviation of the methods were 0.8-3.0%. Percentage recoveries ranged from 97.22% to 102.78%.     

Desorption due to charge exchange in low-energy collisions of organofluorine ions at solid surfaces

Collisions of organofluorine ions at a metal surface result in efficient emission of adsorbate species as gas-phase ions. The experiments are done at 120° scattering angle in a hybrid (BQ) mass spectrometer; the primary ions, mass-selected by a magnetic sector (B), are allowed to collide with a target at a selected kinetic energy in the tens of eV range and the emitted ions are mass-analyzed using a quadrupole mass filter (Q). It is proposed that the impinging ions undergo neutralization accompanied by desorption of hydrocarbon ions and that the amount of internal energy deposited in the desorbed ions is strongly dependent on the collision energy and affects their degree of fragmentation. Competing processes include reflection and fragmentation of the colliding particle, along with such ion/adsorbate reactions as hydrogen atom abstraction by the fluorinated ion. Small even-electron ions, such as [CHF₂]⁺ and [C₂H₂F]⁺ are more effective in promoting chemical sputtering of the surface adsorbate as compared to larger ions (e.g. [C₃F₅]⁺) and odd-electron ions (e.g. [C₂F₄]⁺˙ and [C₂HF₂]⁺˙). At low energies some odd-electron fluorinated ions undergo collision without any secondary ions being emitted from the surface. In these cases the parent ions are apparently neutralized, but without sufficient energy transfer to cause hydrocarbon ion desorption. Non-fluorinated organic ions yield fragment ions and ion/surface reaction products under the condition of these experiments, but do not cause significant desorption of hydrocarbon ions.     

Thiol-functionalized, 1.5-nm gold nanoparticles through ligand exchange reactions: scope and mechanism of ligand exchange

Ligand exchange reactions of 1.5-nm triphenylphosphine-stabilized nanoparticles with omega-functionalized thiols provides a versatile approach to functionalized, 1.5-nm gold nanoparticles from a single precursor. We describe the broad scope of this method and the first mechanistic investigation of thiol-for-phosphine ligand exchanges. The method is convenient and practical and tolerates a surprisingly wide variety of technologically important functional groups while producing very stable nanoparticles that essentially preserve the small core size and size dispersity of the precursor particle. The mechanistic studies reveal a novel three-stage mechanism that can be used to control the extent of ligand exchange. During the first stage of the exchange, AuCl(PPh3) is liberated, followed by replacement of the remaining phosphine ligands as PPh3 (assisted by gold complexes in solution). The final stage involves completion and reorganization of the thiol-based ligand shell.     

Spectrophotometric determination of phenol and resorcinol by reaction with p-aminophenol

Based on the reaction with p-aminophenol, a series of procedures have been developed for the spectrophotometric determination of phenol and resorcinol. Three basic approaches have been studied: (i) a batch procedure, using the dissolved oxygen as oxidant, (ii) a stopped-flow procedure by use of KIO(4) as oxidant and (iii) a flow injection (FI) procedure developed in the presence of KIO(4). Phenol can be accurately determined at 626 nm, in the stopped-flow mode, after a reaction time of 45 min in 0.005M NaOH, 0.004M KIO(4) and 500 mug/ml of PAP. The development of a manifold, which incorporates a sample parking, is a convenient approach which makes it possible to measure, in the stopped-flow mode, four solutions in one hour. The limit of detection of this method corresponds to 64 ng/ml of phenol Resorcinol can be determined by FI at 540 nm in 0.006M NaOH, 0.0002M KIO(4) and 50 mug/ml PAP with a limit of detection of 6.6 ng/ml and a sample throughput of 300 injections per hour. A combination between the FI procedure for the determination of resorcinol and the stopped-flow procedure for phenol determination provides accurate results in the analysis of spiked samples containing both phenol and resorcinol.     

Spectrophotometric determination of aluminium and gallium with pyrogallol red and cetyltrimethylammonium ions

Spectrophotometric methods are described for the determination of microgram amounts of aluminium and gallium based on the formation of a ternary complex between the metal, pyrogallol red, and cetyltrimethylammonium bromide. The complexes have absorbance maxima at 610 and 615 nm, respectively, with molar absorptivities of 4.8 × 10⁴(Al)and 1.0 × 10⁵ liter mol^?1 cm^?1 (Ga). Numerous metals interfere. Gallium can be separated by extraction of gallium from 7 M hydrochloric acid with di-isopropyl ether. However, aluminium can be separated by extraction of interfering ions with cupferron.     

Strong complex formation of carbohydrates with metal ions at alkaline pH studied by ligand exchange chromatography

Summary At alkaline pH, carbohydrates are highly retained on a sulphonated polystyrene resin loaded with rare earth or uranyl metal ions. The complex formation is governed by the ionization of the carbohydrate moiety. pH and the type of metal ion were found to have a decisive influence on the complex formation. Binding of the metal ion to the cation exchanger and to different carbohydrates is described. The competitive complexation between solute and hydroxide to the metal ions is described as a ligand exchange reaction and a retention model is proposed. The ligand exchange column was used as precolumn in a coupled column separation system and the high selectivity is demonstrated by the separation of paracetamol glucuronide from a urine sample after filtration and direct injection.     

Spectrophotometric determination of papaverine hydrochloride by reaction with phloxin

A new withasteroid — vamonolide — has been isolated from the epigeal part ofPhysalis angulata L. (Solanaceae). On the basis of spectral characteristics, its structure has been established as 5,14-dihydroxyl-l-oxo-6,7-epoxy-20R,22R-with-2-enolide.Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 856–858, November–December, 1987.     

利用荷移反应分光光度法测定注射液中的盐酸利多卡因

采用分光光度法研究了电子受体2,3-二氯-5,6-二氰基-1,4-对苯醌(DDBQ)与电子供体利多卡因(LD)的荷移反应,发现DDBQ与LD在乙腈中生成稳定的离子缔合物,并通过Job's plot确定DDBQ和LD的摩尔比为1:1.LD与DDBQ在587nm处形成强特征吸收峰.据此建立了一种测定注射液中LD含量的荷移分...     

特非那定的荷移分光光度法测定

研究了特非那定与甲基红的电荷转移反应,建立了快速测定特非那定的可见分光光度法.结果表明,电荷转移络合物的络合比为1∶1,最大吸收波长是430nm,表观摩尔吸光系数为1.15×104 L·mol-1·cm-1.特非那定质量浓度在0.4~48mg/L范围内服从比耳定律,相关系数为0.998 9.当特非那定浓度为20mg/L时,6次测定结果的相对标准偏差为1.40%.本方法用于测定药物中特非那定的含量,加标回收率为97.8%和101.2%.     

Spectrophotometric determination of papaverine hydrochloride by reaction with phloxin

The optimum conditions for the formation of a complex of papaverine hydrochloride with phloxin have been determined: pH 2.5–3.2. A procedure has been developed for the spectrophotometric determination of papaverine hydrochloride. The sensitivity of the determination is 0.4 µg/ml.Vitebsk Medical Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 836–838, November–December, 1988.