Spectrophotometric determination of silver with cadion 2B and triton X-100

A highly sensitive and selective procedure for spectrophotometric determination of silver has been developed. At pH 9.2, in the presence of Triton X-100, silver forms a dark red-violet complex with cadion 2B which has an absorption maximum at 565 nm. The molar absorptivity is 1.0 x 10(5) l.mole(-1).cm(-1). Beer's law is obeyed for silver in the range 0.02-0.8 mug ml . The colour reaction, if EDTA is used as a masking agent, is free from interference by the 20 cations and 19 anions investigated. Only Cl(-), Br(-), I(-), S(2-) and CN(-) interfere and must be absent. This method has been used to determine silver in waste-water.     

Spectrophotometric study of the system Hg(II)-thymol blue-H2O and its evidence through electrochemical means

The detailed analysis of the experimental spectrophotometric data obtained from solutions containing the acid-base indicator thymol blue (TB) and mercury(II) (Hg(II)) coupled with data processing by means of the SQUAD program, a chemical model was determined that includes the formation of complexes indicator-metal ion (HgTB and HgOTB), dimer species (H3TB2 and H4TB2) and monomer species (HTB and TB). The values of the overall formation constants (log beta) were calculated for the chemical equilibria involved: TB+Hg<-->HgTB log beta=16.047 +/- 0.043, TB+Hg+H2O<-->HgOHTB+H log beta=7.659 +/- 0.049, 2TB+4H<-->H4TB2 log beta=31.398 +/- 0.083, 2TB+3H<-->H3TB2 log beta=29.953 +/- 0.084 and H+TB<-->HTB-log beta=8.900. To compliment the present research, the values of the absorptivity coefficients are included for all the species involved, within a wide range of wavelengths (250-700 nm). The latter were used subsequently to carry simulations of the absorption spectra at various pH values, thus corroborating that the chemical model proposed is fully capable to describe the experimental information. Voltammetric study performed evidenced the formation of a complex with a 1:1 stoichiometry Hg(II):TB.     

Spectrophotometric study of Cd(II), Pb(II), Hg(II) and Zn(II) complexes with 5,10,15,20-tetrakis(4-carboxylphenyl)porphyrin

The reaction of 5,10,15,20-tetrakis(4-carboxylphenyl)porphyrin (TCPP) with Cd(II), Pb(II), Hg(II) and Zn(II) was studied spectrophotometrically and kinetics, equilibrium constants as well as photodecomposition of complexes were determined. It was verified that these metal ions with large radius accelerate the incorporation reaction of zinc into TCPP. On the basis of the mechanism and kinetics of this reaction, a sensitive method for the spectrophotometric determination of trace amounts of Zn(II) has been developed. The molar absorptivity of examined Zn-TCPP complex and Sandell's sensitivity at 423 nm were 3.5×10⁵ M⁻¹ cm⁻¹ and 18.3 ng cm⁻². The detection limit for the recommended procedure was 1.4×10⁻⁹ M (0.9 ng ml⁻¹) and precision in range 20-100 ng ml⁻¹ not exceeds 2.7% RSD. The proposed method applied for zinc determination in natural waters and nutritional supplement was compared with AAS results and declared value.     

显色剂结构与胶束增敏作用的关系 II: Cadion, Cadion 2B的比较

本文从表明活性剂对Cd(II)-Cadion 和Cd(II)-Cadion 2B作用的不同, 研究了有机显色剂分子结构与胶束增敏作用的关系, 发现在无表面活性剂存在时,Cd(II)-Cadion 2B的灵敏度高于Cd(II)-Cadion, 当加入适量表面活性剂后, Cadion体系的增敏效应有如下顺序: SDBS〉混合表面活性剂〉SDS。阳离子表面活性剂无增敏效应。以Triton X-100为例, 分别测定了显色剂及其配合物所在胶束微环境中的D~e~f~f在胶束中的分配系数, 还另用分光光度法和析相法探求增溶位。结果表明: (1)具有两亲结构的被增溶物增溶于胶束的栅状层, 其能否进入栅状层及进入栅状层的深浅, 决定于被增溶物分子的横断面的大小和两亲结构明显程度。(2)在胶束栅状层, 受"刚性不对称微环境"的作用产生增敏作用。(3)从研究Cd(II)-Cadion和Cd(II)-Cadion 2B的分子结构表明: Cd(II)-Cadion 2B的横断面大于Cd(II)-Cadion, 而两亲结构又比Cd(II)-Cadion 不明显, 这是Cd(II)-Cadion 2B胶束增敏率小于Cd(II)-Cadion的主要原因。     

Spectrophotometric study of the reaction of Co(II) and Ni(II) with nitroso-R-salt and α-nitroso-β-naphthol

The complexes of Co(II) and Ni(II) with nitroso-R-salt are studied by conductometric titration and spectrophotometric methods in buffer solutions of differentpH. The study proved the possible formation of (11), (12) and (13) complexes for Co(II) while Ni(II) forms (11) and (12) complexes (metal:ligand) only. The factors affecting complex formation are established and the formation constants of the complexes are evaluated. The ir spectra of the solid complexes with -nitroso--naphthol revealed that the ligand exhibits the nitrosophenol structure and that the reaction takes place through proton displacement from the OH-group.

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Spektrophotometrische Studie zur Reaktion von Co(II) und Ni(II) mit Nitroso-R-Salz und -Nitroso--naphthol

Zusammenfassung Es wurden die Komplexe von Co(II) und Ni(II) mit Nitroso-R-Salz mittels konduktometrischer und spektrophotometrischer Methoden in Puffer-Lösungen mit verschiedenempH untersucht. Für Co(II) wurden (11)-, (12)- und (13)-Komplexe gefunden, während für Ni(II) lediglich (11)- und (12)-Komplexe (Metall:Ligand) festgestellt werden konnten. Die Faktoren, die die Komplexierung bestimmen, werden diskutiert und die Komplexbildungskonstanten wurden bestimmt. Die IR-Spektren der Komplexe mit -Nitroso--naphthol zeigen, daß der Ligand in der Nitrosophenol-Form vorliegt und daß die Reaktion über eine Protonenverschiebung von der OH-Gruppe verläuft.

     

Spectrophotometric study and analytical application of the reaction between manganese(II) and 4-(2-pyridylazo)resorcinol

A highly sensitive method for spectrophotometric determination of manganese(II) with 4-(2-pyridylazo)resorcinol (PAR) as reagent is described. The molar absorptivity of the complex was found to be 8.65 ± 0·04 x 10⁴. The stability constant of the ML₂ complex was found to be log β₂ = 15·6. Beer's law is obeyed within the range 0·02–0·5 μg of Mn/ml. An application of this reaction for analytical purposes is described.     

Spectrophotometric study of the reaction between cobalt(II)-dipeptide complexes and molecular oxygen

Summary The influence of pH and ligand structure on the reaction of cobalt(II) complexes with various dipeptides and molecular oxygen was examined. The minimum pH value required for the formation of dioxygen adducts was found to be about 6.5. This value should be related to amidic deprotonation of dipeptides, which seems to occur in the examined systems at particularly low values. The location and steric hindrance of the side chains of the dipeptides have a strong influence on the reaction rate. The presence of a substituent group on the N-terminal amino acid promotes oxygen coordination, while, when the substituent group is on the C-terminal residual, a decrease of reaction rate is observed.A stabilizing effect of the aromatic ring on the dioxygen adducts is found only when the substituent is in the C-terminal position, and seems to be independent of the presence of additional coordinating groups.Some information regarding the mechanism of the irreversible decomposition of the cobalt(II) complexes has been obtained by studying the effect of pH and ligand structure on the reaction rate.Work supported by National Research Council of Italy.     

Spectrophotometric study of the complex formation of 3-(2-hydroxyphenyl)-2-mercaptopropenoic acid with Ni(II) and Zn(II)

The dissociation and complex formation equilibria between Ni(II) and Zn(II) with 3-(2-hydroxyphenyl)-2-mercaptopropenoic acid, at 25 degrees in aqueous 0.1 and 1.0M sodium perchlorate solutions, containing about 1% ethanol, have been studied spectrophotometrically. The data were connected directly from the spectrophotometer to an IBM-PC via a serial interface, using the DUMOD program (written in BASIC), described in the paper. The obtained spectra were treated by the factor analysis program NIPALS in order to determine the number of absorbing species and the experimental error. Dissociation constants of ligand (H(3)L), and formation constants for the complexes Ni(HL), Ni(HL)(2), Zn(HL) and Zn(HL)(2) at 0.1 and 1.0M ionic strengths, refined by the SQUAD program, are reported.     

Indirect determination of Hg(II) based on reaction with metallic silver

Ohne Zusammenfassung

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Thin-layer chromatographic separation of fluorescent amino acid derivatives of 5-isothiocyanato-1,3-dioxo-2-p-tolyl-2,3-dihydro-1H-benz[de]isoquinoline

Teile der Dissertationen von H. Görgen und J. Dörpinghaus, Med. Hochschule Hannover, 1978     

Spectrophotometric study of the reaction of the uranyl ion with 4-(2-thiazolylazo) resorcinol

The uranyl ion forms only 1:1 chelates with 4-(2-thiazolylazo) resorcinol (TAR) in solution, UO(2)(TAR)H(+) being formed below pH 3 and UOS(TAR) above pH 3-5. The latter complex may also be precipitated at pH > 3. The quantitative formation of UO(2)(TAR) at pH 7.5-7.8 in solutions containing a small excess of reagent and some triethanolamine as buffer can be used for the sensitive spectrophotometric determination of uranium. Several interfering ions can be masked with a mixture of sodium fluoride, cyclohexanediaminetetraacetic acid and 5-sulphosalicylic acid. TAR is slightly less sensitive than 4-(2-pyridylazo)resorcinol as a reagent for uranium but is more selective.     

Spectrophotometric study of the reaction of gallium(III) with xylenol orange

The formation of complexes between gallium(III) and Xylenol Orange at pH 2 has been studied. Complexes with the mole ratio 1:1 and 1:2 have been found and the respective formation constants determined. The latter complex, for which the absorption spectrum has been calculated, is suitable for the spectrophotometric determination of gallium, and optimum conditions for its formation have been established.     

Spectrophotometric study of the reaction of iron(iii) with methylthymol blue

The reaction between iron(III) and Methylthymol Blue (MTB or H(6)A) has been investigated by spectrophotometry. It has been established that iron(III) and MTB form two complexes with compositions iron(III): MTB = 1:1 and 1:2. The 1:1 complex is stable in acidic medium containing excess of iron, and the 1:2 complex is stable in slightly acidic or alkaline media containing excess of MTB. The absorption maxima are at 610 mmu (1:1) and 515 mmu (1:2), the molar absorptivities being 1.73 +/- 0.01 x 10(4) and 3.21 +/- 0.05 x 10(3) respectively. The nature of the two complexes at pH 6 and the stability constants have been determined: log beta(11) = 20.56 +/- 0.07, log beta(112) = 43.29 +/- 0.09, log beta(12) = 6.66 +/- 0.05.     

Spectrophotometric study of the reaction of bismuth(III) with Xylenol Orange

The reaction between bismuth(III) and Xylenol Orange (XO) has been investigated by spectrophotometry. It has been established that bismuth(III) and Xylenol Orange form complex compounds with compositions Bi(III):XO = 1:1 (up to pH 1) and Bi(III):XO = 1:2 (above pH 1) which have absorption maxima at 550 and 500 nm respectively. The formula of the 1:1 complex is [Bi(H(3)R)] whereas the 1:2 complex can take one of the following forms: [Bi(H(4)R)(2)](1-), [Bi(H(4)R)(H(3)R)](2-) and [Bi(H(3)R)(2)](3-). If the values for pK(Bi(H(3)R)) and pK(Bi(H(3)R)(2)) respectively are 9.80 +/- 0.03 and 15.53 +/- 0.03 at a constant ionic strength of 1.0.     

Spectrophotometric and polarographic study of pyridine-2-aldehyde guanylhydrazone-Cu(II) complex

The reaction between Cu(II) and pyridine-2-aldehyde guanylhydrazone nitrate (PAG) was investigated by using the techniques of spectrophotometry and polarography.A spectrophotometric determination of Cu(II) with PAG can be performed in a concentration range varying from 0.39–5.50 ppm of copper; the molar absorptivity is 1.2 × 10⁴ liters mole^?1 cm^?1 at 380 nm and the relative error is ±0.6%.The complex gave rise to a single well defined cathodic wave ($\text{E}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= ?0.34 V}\text{for pH}\text{= 8.1}$). The reduction process is diffusion controlled, involves two electrons, and is irreversible.The stoichiometry 1:1 of the complex was established by different methods and by both techniques. The apparent stability constants were computed as log K = 4.4 ± 0.1 and 4.7 from spectrophotometric and polarographic techniques, respectively.     

A thermodynamic study of the complexation reaction of beryllium(II), magnesium(II) and calcium(II) with 3-hydroxy-2-naphtoic acid

The thermodynamic stability constants and thermodynamic parameters for the complexation reaction of Be²⁺, Mg²⁺ and Ca²⁺ with 3-hydroxy-2-naphthoic acid have been determined pH metrically in a 70% v/v dioxane-water medium in the presence of potassium nitrate. The study showed the formation 1:1 and 1:2 complexes of Be²⁺, Mg²⁺ and 1:1 complex of Ca²⁺ with 3-hydroxy-2-naphthoic acid. The order of overall stability is Be²⁺>Mg²⁺>Ca²⁺.     

Spectrophotometric study of etodolac complexes with copper (II) and iron (III)

A rapid, simple, and selective method was developed for the determination of etodolac. The method depends on complexation of etodolac with copper (II) acetate and iron (III) chloride followed by extraction of complexes with dichloromethane and then measuring the extracted complexes spectrophotometrically at 684 and 385 nm in case of Cu (II) or Fe (III), respectively. Different factors affecting the reaction, such as pH, reagent concentration, and time, were studied. By use of Job's method of continuous variation, the molar ratio method, and elemental analysis, the stoichiometry of the reaction was found to be in the ratio of 1:2 and 1:3, metal:drug in the case of Cu (II) and Fe (III), respectively. The method obeys Beer's law in a concentration range of 2.00-9.00 and 0.50-2.00 mg/mL in case of Cu (II) and Fe (III), respectively. The stability of the complexes formed was also studied, and the reaction products were isolated for further investigation. The complexes have apparent molar absorptivities of about 32.14 +/- 0.97 and 168.32 +/- 1.12 for Cu (II) and Fe (III), respectively. The suggested procedures were successfully applied to the analysis of pure etodolac and its pharmaceutical formulations. The validity of the procedures was further ascertained by the method of standard additions, and the results were compared with other reported spectrophotometric methods and showed no significant difference in accuracy and precision.     

Spectrophotometric study of coproporphyrin-I complexes of copper(II) and cobalt(II)

The reagent 3,8,13,18-tetramethyl-21H,23H-porphine-2,7,12,17-tetrapropionic acid or coproporphyrin-I (CPI) was used for the spectrophotometric determination of copper(II) and cobalt(II) in the presence of pyridine and imidazole catalysts. Optimum conditions were investigated and the methods were applied to the determination of parts per billion levels of copper(II) and cobalt(II). The Sandell sensitivities of the recommended procedures were 0.568 μm cm⁻² and 0.464 μg cm⁻² (for A = 0.001) for copper and cobalt, respectively. The relative standard deviations were 2.0% for copper and 1.0% for cobalt. The kinetics of the reaction of CPI with copper(II) and cobalt(II) in the presence of the catalysts and the influence of the temperature were studied, and their kinetic constants determined.The influence of light on the photodecomposition of CPI was also studied.     

Water-activity and double-layer effects on the Fe(II)/Fe(Hg) reaction

The title subject is studied by electrode-kinetic measurements in acetate buffered potassium chloride and magnesium sulphate solutions of varied concentration at 25°C, using literature data for activity and double-layer properties. The results indicate that the Fe(II)/Fe(Hg) reaction occurs by an essentially symmetric (α near 1/2) ferrous-ion transfer (n=2), that this transfer is second order in water-activity dependence, and that it exhibits a smaller than classically expected double-layer effect. No specific interaction appears for any of the ions of the supporting salts. An e.c. reaction scheme is proposed for the Fe(Hg)/Fe(II) electrode in non-complexing aqueous solution.     

Spectrophotometric study of the chelate of palladium(II) with methylthymol blue

Methylthymol blue reacts very sensitively with palladium(II) to form two complexes. The 1:1 complex has λ_max at 530 nm in acidity range 0.02 to 0.05 M with respect to perchloric acid and 1:2 (metal reagent ratio) complex at 500 nm in pH range 6.8 to 7.5. Optimum conditions including the range for adherence to Beer's law, effect of pH, effect of excess reagent and sensitivity are reported for the photometric determination of palladium using methylthymol blue.     

Spectrophotometric study of pseudopurpurin-Pd(II) dimer complex. Spectrophotometric determination of traces of Pd(II)

We have studied spectrophotometrically the Pseudopurpurin-Pd(II) complex in an ethanolic-water medium ¦Ethanolamine ¦_optimum = 4 × 10⁻¹M; λ = 670 nm; 20% H₂O; stable for at least 4 hr; ¦Reagent¦_optimum = 5 × 10⁻⁵M; stoichiometry 2:2; log K = 17.7. A new method for the spectrophotometric determination of Pd traces is proposed for concentrations between 0.30 and 2.40 ppm. The relative error and the interferences of the method have been investigated.