Indirect spectrophotometric determination of trace cyanide with cationic porphyrins

Three highly sensitive methods for the determination of cyanide have been developed, based on the fact that the complexation of silver ions with three cationic porphyrins, 5,10,15,20-tetrakis-(1-methyl-2-pyridinio)porphine [T(2-MPy)P], 5,10,15,20-tetrakis(1-methyl-3-pyridinio)porphine [T(3-MPy)P] and 5,10,15,20-tetrakis(1-methyl-4-pyridinio)porphine [T(4-MPy)P], in alkaline media is inhibited by cyanide and the decrease in absorbance of the silver(II) complex is proportional to the cyanide concentration. Sensitivities of the procedures developed are 0.133, 0.126 and 0.234 ng/cm(2), respectively for an absorbance of 0.001. Cadmium(II), copper(II), mercury(II), zinc(II), iodide and sulfide interfere with the cyanide determination. One of the proposed methods was applied to the determination of cyanide in waste-water samples, with satisfactory results.     

Determination of cyanide by a highly sensitive indirect spectrophotometric method

Complexation of Pd(2+) with cyanide inhibits the extraction of the palladium complex of 5-phenylazo-8-aminoquinoline. This effect is used for the indirect spectrophotometric determination of cyanide at the mug level. Cyanide in industrial waste water and in sea-water is determined after distillation as HCN from the sample and collection in sodium hydroxide solution.     

Novel reactions for simple and sensitive spectrophotometric determination of nitrite

Nine spectrophotometric methods based on new reactions for the determination of tracer amounts of nitrite in environmental samples were developed. Replacement of toxic reagents was explored to attain the standards of clean chemistry. These methods utilize two classes of compounds namely; phenoxazines and sulphonamides, the well established drugs in the presence of limited amounts of hydrochloric acid. The methods were based on the oxidation of sulfanilamide (SAA), sulfadoxine (SDX) or sulfamethoxazole (SMX) by nitrite in hydrochloric acid medium and coupling with phenoxazine (PNZ), 2-chlorophenoxazine (CPN) or 2-trifluoromethylphenoxazine (TPN) which yielded red colored derivatives having an absorbance maximum in the range 530-540 nm and were stable for about 4 h. Beer's law was obeyed for nitrite in the concentration range 0.13-1.60 μg mL⁻¹. The reaction conditions and other important analytical parameters were optimized to enhance the sensitivity of the methods. Interference if any, by non-target ions was also investigated. The methods were applied determining nitrite in environmental samples. The performance of these methods were evaluated in terms of Student's t-test and variance ratio F-test to find out the significance of proposed methods over the reference spectrophotometric method.     

动力学抑制光度法测定氨三乙酸

氨三乙酸在分析化学中常作为配位滴定剂和掩蔽剂,在催化动力学分析中常作为活化剂。常量的氨三乙酸的测定已有工业化方法,微量氨三乙酸的测定方法极少。酸性和沸水浴条件下,微量的氨三乙酸对高碘酸钾氧化偶氮胭脂红B褪色的反应具有显著的抑制作用,据此建立     

铟的灵敏光度测定法

我国对微量铟的显色反应研究得较少.最常用的是碱性染料萃取光度法,但操作冗繁而且苯的毒性较大.因此寻找灵敏度高而又能在水相测定铟的新方法是很有必要的. 用苯荧光酮(2,3,7-三羟基-9-苯基-6-荧光酮,PF)作显色剂的胶束增溶分光光度法已应用于锗、钼、锡、镓等的测定,但用类似的方法测铟则尚未见报道.我们的实验证明,在pH为7.7～8.9的醋酸-氢氧化铵缓冲介质中,铟与PF及氯化十六烷基吡啶(OPC)生成玫瑰红色的三元配合物,其配合比为In(III):PF:CPC=1:2:2,表观稳定常数为8.6×10~(10),摩尔吸收系数达1.28×10~5.提出用乙酸乙酯萃取分离杂质.利用本显色反应测定微量铟,方法灵敏且稳定,准确度和精密度均较好.     

一种简单灵敏的光度法测定环境水样中痕量对苯二酚

在SCN -存在下,控制溶液pH5.0,对苯二酚使Cu(Ⅱ)还原生成的Cu(Ⅰ)与SCN -反应生成CuSCN沉淀,通过测定溶液中剩余Cu(Ⅱ)的量,可以测定对苯二酚的含量.吸光度与对苯二酚含量之间存在良好线性关系.线性方程:A =4.567 +0.9726ρ(μg/mL),线性范围为0.16～4.0μg/mL,相关系...     

A sensitive spectrophotometric method for the determination of desloratadine in tablets

A simple, rapid, and sensitive visible spectrophotometric method was developed, for the first time, for analysis of desloratadine (DE) in tablets. The method is based on the deep-blue colored TCNQ*- radical anion formed by interaction of the drug (n-donor) with 7,7,8,8-tetracyanoquinodimethane (TCNQ, pi-acceptor) in acetonitrile at ambient temperature. Optimum conditions for the reaction were investigated, absorbances were read at 843 nm, and the linearity range for concentrations of DE was found to be 1.5-13 microg/mL. The reaction product remains stable up to 8 h when kept at room temperature in the dark. The developed method was validated and successfully applied to the determination of DE in tablets. The tablets were also analyzed with a column liquid chromatography method reported in literature. The results from both methods were statistically compared by t- and F-tests. No significant difference was found for the means and standard deviations at 95% confidence level. Accuracy was examined through recovery studies. Being very simple and reliable, the method can be recommended for routine quality control analysis of DE in tablets.     

A sensitive method for the ultraviolet spectrophotometric determination of chloride

A new method for the determination of chloride ion is based on the formation of phenylmercury(II) chloride, its extraction into chloroform and reaction with sodium diethyldithiocarbamate to form phenylmercury(II) diethyldithiocarbamate. This complex has spectral maxima at 257 and 297 nm. either of which can he used for quantitative purposes. The molar absorptivities are 21.3·10³ and 6.5·10³ respectively. referred to the chloride ion. The method is especially suitable for the determination of trace amounts of chloride in aqueous solution and has been applied to samples of drinking water. Amounts of chloride in the range 0.04 0.32 p.p.m. can be determined in 250-ml aqueous samples with an average relative mean error of 12%. The method can be used also for bromide and iodide, and for organomercury(11) compounds. Interferences are minimal and the method compares favourably with the standard mercury(II) thiocyanate procedure.     

Flow injection spectrophotometric determination of cyanide by the phenolphthalin method

The phenolphthalin method for the determination of cyanide has been modified and adapted to a continuous flow system based on the flow injection principle. Aqueous cyanide samples are injected into a carrier stream (0.001 M NaOH), which is then merged with the combined reagent stream of phenolphthalin and carbonate buffer (pH 10.3), and the mixture is passed through an on-line cupric sulfide packed column. The resulting phenolphthalein (the oxidized form of phenolphthalin) is measured in a flow-through spectrophotometer at 552 nm, to determine the cyanide content. The chemical factors and flow injection analysis (FIA) variables influencing the system are discussed. The calibration graph is linear from 0.6 to 4.3 ppm cyanide. At a sampling rate of about 70 samples h(-1) with 50 mul sample injections, precision was about 1% relative S.D.     

Indirect spectrophotometric determination of cyanide

A spectrophotometric method for cyanide based on its inhibition of the colour formation reaction between nickel(II) and 3-(4,5-dimethyl-2-thiazolylazo)-2,6-dihydroxybenzoic acid has been developed, and allows the determination of down to 0.1 g of cyanide. Most of the interferences can be avoided by displacement of the hydrogen cyanide using an arsine generator.     

New spectrophotometric method for the determination of trace amounts of palladium

Summary A simple, rapid, selective, and sensitive method for the spectrophotometric determination of palladium is developed based on the reaction of Pd(II) with 1-amino-4-hydroxyanthraquinone (AMHA). The reaction is carried out atpH 3.8 in 50% (v/v) ethanol-water medium. The molar absorptivity of the complexed ligand is 1.1 · 10⁴ l mol^–1 cm^–1 at 620 nm. Calibration plots are linear up to 17 µg Pd cm^–3. The optimum concentration range (Ringbom plot) is between 3–14.5 µg cm^–3. The spectral study of the reaction in solutions containing equimolar concentrations or an excess of one component, in thepH range 0.3–6.5, indicate the possible complex transitions that occur in solution. Complete graphical and logarithmic analysis of the absorbance-pH graphs was performed to demonstrate and characterize the complexation equilibria in solution. Under the optimum conditions, palladium can be determined as the noncharged complex Pd(AMHA)₂ in the presence of a large number of foreign ions. Interferences caused by zirconium(IV) could be masked with fluoride ions.

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Eine neue spektrophotometrische Methode für die Bestimmung von Palladium in Spuren

Zusammenfassung Eine einfache, schnelle und empfindliche Methode für die spektrophotometrische Bestimmung von Palladium wurde auf der Basis der Reaktion von Pd(II) mit 1-Amino-4-hydroxyanthrachinon (AMHA) entwickelt. Die Reaktion wird in 50% (v/v) Ethanol/Wasser beipH 3.8 ausgeführt. Die molare Absorption des komplexierten Liganden beträgt 1.1 · 10⁴ l mol^–1 cm^–1 bei 620 nm. Kalibrierungskurven verlaufen bis zu 17 µg Pd cm^–3 linear. Der optimale Konzentrationsbereich (Ringbom-Plot) liegt zwischen 3 und 14.5 µg cm^–3. Spektroskopische Untersuchungen der Reaktion in Lösungen, entweder mit equimolaren Konzentrationen oder mit einem Überschuß an einer Komponente impH-Bereich 0.3–6.5, lassen Rückschlüsse auf mögliche Komplex-Übergänge in Lösung zu. Es wurde eine vollständige graphische, logarithmische Analyse der Absorptions-pH-Graphen durchgeführt, um die Komplexgleichgewichte in Lösung aufzuklären und zu charakterisieren. Unter den Optimalbedingungen kann Palladium als nichtgeladener Komplex Pd(AMHA)₂ in Gegenwart einer großen Anzahl an Fremd-Ionen bestimmt werden. Schwierigkeiten mit Zirkonium(IV) konnte durch Maskierung mit Fluorid-Ionen umgangen werden.

     

Indirect determination of free cyanide in industrial waste effluent by atomic absorption spectrometry

An indirect method is described for the determination of free cyanide in industrial waste effluent samples by atomic absorption spectrometry (AAS). In an alkaline medium, cyanide forms a stable complex species [Cu(BPTC)(CN)] (BPTC = 2-benzoylpyridine thiosemicarbazone), which can be extracted into a mixture of isobutyl methyl ketone-isopentyl alcohol (7 + 1) with an efficiency of greater than 98.5%. The extract can be analysed directly for copper (and hence indirectly for cyanide) by flame AAS. The calibration graph is linear up to 5.7 micrograms of cyanide per millilitre of solvent mixture and the limit of detection is 4.8 ng ml-1. A large number of foreign ions were found not to interfere with the proposed method.     

Novel spectrophotometric method for the determination of molybdenum in a PVA medium.

A novel spectrophotometric method for the determination of trace molybdenum in the presence of a large amount of tungsten was developed. This proposed method was based on the formation of a green charge-transfer polyoxometalate, molybdo-11-tungstophosphate-3,3',5,5'-tetramethylbenzidine-N-propanesulfonic, which was solubilized and stabilized in a PVA medium; the wavelength of the maximum absorption was at 660 nm. Beer's law was obeyed in the Mo concentration range of 0.04-1.6 microg ml(-1). The molar absorptivity was 1.35 x 10(4) l mol(-1) cm(-1). The developed method avoided the interference of W(VI), and was conveniently applied to analyses of some tungsten ores containing Mo(VI) with satisfactory results.     

Kinetic spectrophotometric method for rapid determination of trace formaldehyde in foods

A simple and sensitive kinetic-spectrophotometric method was developed for the determination of ultra trace amount of formaldehyde in food samples. The method was based on the oxidation of rhodamine B (RhB) by potassium bromate in sulfuric acid medium (formaldehyde as catalyst). The reaction was monitored by measuring the decrease in absorbance of the dye at 515 nm after 6 min. The developed method allowed the determination of formaldehyde in the range of 10–100 μg L⁻¹ with good precision, accuracy and the detection limit was down to 2.90 μg L⁻¹. The relative standard deviations for the determination of 10 and 60 μg L⁻¹ of formaldehyde were 3.0% and 1.9% (n = 10), respectively. The method was found to be sensitive, selective and was applied to the determination of formaldehyde in foods with satisfactory results.     

A sensitive spectrophotometric method for the determination of trace amounts of uranium (VI) using o-hydroxypropiophenone isonicotinoyl hydrazone

The reaction between uranium (VI) and o-hydroxypropiophenone isonicotinoyl hydrazone (OHPINH) has been investigated in HCl-sodium acetate buffers and a highly sensitive and simple procedure for the determination of uranium (VI) is suggested. The yellow colored complex showed maximum absorption at 380 nm in buffer solutions of pH 3. Beer's law is obeyed in the range of 0.47–17 g ml^–1. The molar absorptivity and Sandell sensitivity are found to be 1.15×10⁴ dm³ mol^–1 cm^–1 and 0.02 g cm^–2, respectively. The composition of the complex is found to be 11 between metal and reagent.     

A chemical enhancement method for the spectrophotometric determination of trace amounts of arsenic

A highly sensitive spectrophotometric method for the determination of 0.03-1.0 microg of arsenic is described. After extraction as AsI(3) into benzene, it is selectively stripped into water. Both the arsenic(III) and iodide present in the aqueous phase are made to react with iodate in acidic medium in the presence of chloride to form the anionic chloro complex, ICl(-)(2). The determination is completed after extraction of ICl(-)(2) species as an ion-pair with Rhodamine 6G into benzene and measuring the absorption of the extract at 535 nm. The coefficient of variation is 1.5% for 10 determinations of 0.5 microg of arsenic. The method has been applied to the determination of arsenic content in plant materials, high purity iron, copper base alloys and inorganic arsenic levels of natural waters.     

Flow injection kinetic spectrophotometric method for the determination of trace amounts of nitrite

In this work, a new, simple and sensitive flow injection catalytic kinetic spectrophotometric determination of nitrite is reported based on catalytic effect of nitrite on the redox reaction between sulfonazo III and potassium bromate in acidic media. The reaction was monitored by measuring the decrease in the absorbance of sulfunazo III at 570 nm. Various chemical (such as the effect of acidity, reagents concentrations) and instrumental parameters (flow rate, reaction coil length, injection volume and temperature) were studied and were optimized. Under the optimum conditions calibration graph was linear in the nitrite concentration ranges of 8.00 × 10⁻³-3.00 × 10⁻¹ μg/ml (with slope of 2.40) and 3.50 × 10⁻¹-1.80 μg/ml (with slope of 0.42). The detection limit was 6.00 × 10⁻³ μg/ml of nitrite, the relative standard deviation (n = 10) was 1.25% and 0.88% for 5.00 × 10⁻² and 2.00 × 10⁻¹ μg/ml of nitrite respectively. About 60 samples in 1 h can be analyzed. The interfering effects of various chemical species were studied. The method was successfully applied in the determination of nitrite in food and environmental samples.     

A sensitive spectrophotometric method for the determination of methyl alcohol in air and water

A sensitive spectrophotometric method for the indirect determination of methyl alcohol in air and water is described. The methyl alcohol is oxidized to formaldehyde which is then determined in acidic medium with p-aminoazobenzene and sulphur dioxide. Beer's law is obeyed in the range 100-600 mug of methyl alcohol in 25 ml of final solution and the wavelength of maximum absorption is 505 nm. The lower limit of determination is 5 mug ml in the sample. Several common organic co-pollutants do not interfere. The method can be used for determination of methyl alcohol in blood.     

Study of colour-developing factors in spectrophotometric determination of cyanide by the pyridine-barbituric acid method

Summary The decomposition of cyanide-pyridine-barbituric acid in the wavelength around _max=583 nm gives rise to formation of a new color species around _max=490nm. Both reactions are first-order reactions with the same K value of 0.066 hr^–1, but with opposite sign. The pH value, the nature and concentration of the buffer solution influence absorption to a considerable extent. A method for estimation of cyanide is suggested.

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Untersuchung der Farbbildungsfaktoren bei der spektrophotometrischen Bestimmung von Cyanid nach der Pyridin-Barbitursäure-Methode

Zusammenfassung Die Zersetzung von Cyanid-Pyridin-Barbitursäure bei der Bandbreite um _max=583 nm verursacht die Bildung einer neuen Farbspecies um _max=490 nm. Beide Reaktionen sind solche erster Ordnung mit dem selben K-Wert von 0,066 hr^–1, aber mit umgekehrtem Vorzeichen. pH-Wert, Art und Konzentration der Pufferlösung beeinflussen die Absorption in beträchtlichem Maß. Eine Methode zur Bestimmung von Cyanid wird vorgeschlagen.