Simultaneous spectrophotometric determination of cobalt,copper and nickel using 1-（2-thiazolylazo）-2-naphthol by chemometrics methods

The simultaneous determination of cobalt, copper and nickel using 1-（2-thiazolylazo）-2-naphthol （first figure of this article） by spectrophotometric method is a difficult problem in analytical chemistry, due to spectral interferences. By multivariate calibration methods, such as partial least squares （PLS） regression, it is possible to obtain a model adjusted to the concentration values of the mixtures used in the calibration range. Orthogonal signal correction （OSC） is a preprocessing technique used for removing the information unrelated to the target variables based on constrained principal component analysis. OSC is a suitable preprocessing method for PLS calibration of mixtures without loss of prediction capacity using spectrophotometric method. In this study, the calibration model is based on absorption spectra in the 550-750-nm range for 21 different mixtures of cobalt, copper and nickel. Calibration matrices were formed from samples containing 0.05-1.05, 0.05-1.30 and 0.05-0.80 μg·mL^-1 for cobalt, copper and nickel, respectively. The root mean square error of prediction （RMSEP） for cobalt, copper and nickel with OSC and without OSC were 0.007, 0.008, 0.011 and 0.031,0.037, 0.032 μg· mL^-1, respectively. This procedure allows the simultaneous determination of cobalt, copper and nickel in synthetic and real samples and good reliability of the determination was proved.     

Spectrophotometric determination of indium in nickel alloys and zinc ores with 1-(2-pyridylmethylideneamine)-3-(salicylideneamine)thiourea

A sensitive method for the spectrophotometric determination of indium with 1-(2-pyridylmethylideneamine)-3-(salicylideneamine)thiourea is proposed. A yellow complex is formed at pH 4.5 (succinate buffer) in a medium containing 40% dimethylformamide, and the absorbance is measured at 415 nm. The molar absorptivity is 6.2 x 10(4)l.mole(-1).cm(-1). The relative standard deviation of the procedure is 1.5%. The method has been applied to determination of indium in a nickel alloy and three zinc ores, with prior isolation of indium by co-precipitation with ammonia and extraction into n-butyl acetate from 5M hydrobromic acid.     

Selective determination of cobalt using polyurethane foam and 2-(2-benzothiazolylazo)-2-p-cresol as a spectrophotometric reagent

The present work describes a selective, rapid and economical method for the determination of cobalt using the 2-(2-benzothiazolylazo)-p-cresol (BTAC) as a spectrophotometric reagent associated with a solid extraction on polyurethane foam. The BTAC reacts with Co(II) in the presence of Triton-X100 surfactant forming a green complex with maximum absorption at 615 nm. The reaction is used for cobalt determination within a pH range of 6.50-7.50, with an apparent molar absorptivity of 1.62 x 10(4) L mol(-1) cm(-1). Beer's Law is obeyed for a concentration of at least 1.60 microg ml(-1). A selective procedure is proposed for cobalt determination in the presence of Fe(II), Hg(II), Zn(II) and Cu(II) up to milligram levels using masking agents. Polyurethane foam is used for the preconcentration and separation of cobalt from thiocyanate media and this procedure is applied to its determination in nickel salts and steel alloys.     

Simultaneous derivative spectrophotometric determination of zinc and cadmium with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol in the presence of cetylpyridinium chloride.

A selective and sensitive derivative photometric method has been developed for the determination of trace amounts of Zn2+ with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol in the presence of cetylpyridinium chloride, a cationic surfactant. The molar-absorption coefficient and analytical sensitivity of the 1:2 complex at 554 nm are 1.19 x 10(5) L mol(-1) cm(-1) and 0.56 ng mL(-1), respectively. The detection limit is 1.96 x 10(-2) ng mL(-1) and Beer's law is valid in the 0.02-0.66 microg mL(-1) range of Zn2+. The developed derivative procedure, using the zero-crossing measurement approach, is applied for the rapid and selective simultaneous determination of Zn2+ and Cd2+ in the range of 0.06-0.66 and 0.20-1.60 microg mL(-1), respectively. Complex matrices, including reference materials, environmental and biological samples and synthetic mixtures, have been successfully analyzed for trace amounts of the two metal ions.     

Chromatographic behavior of open-chain polyamines NH2-(CH2)2-[NH-(CH2)2]n-NH2 and their quantitative determination in sea water by high-performance ion-exchange chromatography

The results are reported of a study using high-performance liquid chromatography for the chromatographic behavior of a homologous series of open-chain polyamines having the general molecular formula NH2-(CH2)2-[NH-(CH2)2]n-NH2 (n = 0-4). The exchange column is a carboxylate-functionalized resin. Amines are eluted with mixtures of HClO4 0.200 mol/L, NaClO4 from 0.100 to 1.40 mol/L, and acetonitrile (ACN) from 0% to 40% (v/v) and detected amperometrically. The dependence of the retention factor k' on sodium and ACN concentrations in the eluent and the total number of nitrogen atoms in the amines are considered and discussed. Suitable relationships are derived. Examples of polyamines separation are given, and a quantitative determination of analytes in spiked sea water is shown.     

Spectrophotometric determination of uranium(VI) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol in a flow-injection system

The direct determination of uranium(VI) by a flow-injection procedure is based on spectrophotometric measurement with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol in the present of fluoride. The interfering effects of many commonly occuring elements were studied. The calibration curve was linear over the range 0.5–20 mg 1^?1 uranium(VI). The relative standard deviation obtained on a leach liquor containing 10 mg 1^?1 uranium(VI) was 1.9%. The procedure is rapid and convenient, and up to 40 samples can be analysed per hour.     

Sensitive spectrophotometric determination of nickel(II) with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol

A simple, selective and highly sensitive procedure for spectrophotometric determination of nickel has been developed. At pH 5.5, nickel reacts with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol in water-ethanol medium to form a red-violet complex which has two absorption maxima, at 520 and 56Onm. The molar absorptivity at 56Onm is 1.26 x 10(5) l.mole(-1).cm(-1). Beer's law is obeyed for 0-15 mug of nickel. Nickel in aluminium alloys and electroplating waste-water has been determined by this method.     

Simultaneous Determination of Platinum and Palladium by Second Derivative Spectrophotometry Using 3-(2'-Thiazolylazo)-2, 6-Diaminopyridine as Chromophore Ligand

ABSTRACT

A second derivative spectrophotometric method has been developed for the determination of palladium and platinum in mixtures. The method is based on the formation of the platinum and palladium complexes with 3-(2-thiazolylazo)-2, 6-diaminopyridine, (2, 6-TADAP), in the presence of 1.7 M perchloric acid solution, upon heating at 90° C for 30 min and on the subsequent direct derivative spectrophotometric measurement. The zero-crossing approach and the graphic method were used for determination of platinum and palladium, respectively. Each analyte was determinated in the presence of one another in the ranges 8.9×10^-7 -3.1×10^-5 M for platinum and 4.6×10^-7 - 6.8×10^-5 M, for palladium. The detection limits achieved (3a) were found to be 2.7×10^-7 M of platinum and 1.4×10^-7 M of palladium. The relative standard deviations were in all instances less than 1.0%. In this work is included a study of effect of interferents and the application of the proposed method in synthetic mixtures.     

Extraction spectrophotometric determination of maneb with 1-(2'-pyridylazo)-2-naphthol (PAN)

A rapid, sensitive, simple and selective spectrophotometric method has been developed for the determination of micro-quantities of maneb (manganese ethylenebisdithiocarbamate) after extraction of the manganese-PAN complex in isobutyl methyl ketone (MIBK). The complex absorbs strongly at 550 nm. Beer's law is obeyed over the concentration range 0.37-3.75 microg/ml. The molar absorptivity was found to be 4.1 x 10(4) l. mole(-1) . cm(-1). The developed method has been applied to the determination of maneb in commercial formulations, synthetic mixtures, grain and in the presence of various other dithiocarbamates.     

Multiwavelength spectrophotometric determination of acidity constants of 1-（2-thiazolylazo）-2-naphthol in methanol-water mixtures

The acid-base properties of 1-(2-thiazolylazo)-2-naphthol (TAN) in mixtures of methanol-water at 25℃and an ionic strength of 0.1 mol/L are studied by a multi-wavelength spectrophotometric method.The acidity constants of all related equilibria are estimated using the whole spectral fitting of the collected data to an established factor analysis model DATAN program was used for determination of acidity constants.The corresponding pK_a values in methanol-water mixtures were determined.There is a linear relationship between acidity constants and the mole fraction of methanol in the solvent mixtures.     

Zero-crossing second derivative spectrophotometry for simultaneous determination of palladium and nickel using 1-(2-pyridylazo)-2-naphthol in mixed micellar solutions

1-(2-Pyridylazo)-2-naphthol (PAN) has been used for the simultaneous determination of nickel and palladium at trace levels. PAN complexes of nickel and palladium in the pH 1.98 form red and green colored complexes, respectively, which are soluble in aqueous 4:1 Triton X-100 to sodium dodecylsulfate (SDS) micellar media with total detergent concentration of 3.2%. Under optimum conditions, calibration graphs for the simultaneous determination by second derivative spectrophotometry were obtained. Zero crossing second derivative spectrophotometry at 668 and 572 nm, respectively for palladium and nickel was used for the simultaneous determination. The method is able to determine palladium to nickel ratio 70:1 to 1:6 (Wt/Wt), accurately. Accuracy and reproducibility of the determination method on the known various amounts of palladium and nickel in their binary mixtures were tested. Effects of diverse ions on the determination of palladium and nickel to investigate selectivity of the method also were studied.     

Extraction and sensitive spectrophotometric determination of ytterbium with 2-(3,5-dichloro-2-pyridylazo)-5-dimethylaminophenol

The operating conditions for the absorptiometric determination of Yb(III) with the reagent 2-(3,5-dichloro-2-pyridylazo)-5-dimethylaminophenol (3,5-diClDMPAP) by a liquid—liquid extraction technique are presented. The complex yields a molar absorptivity of 1.54 × 10⁵l.mole⁻¹.cm⁻¹ (λ_max = 588 nm) and an optimum concentration range of 0.025–1.360n mg/l., at pH = 10. The method developed has been applied to the determination of Yb(III) in synthetic and concrete mixtures.     

Spectrophotometric determination of mercury with 5-(6-methyl-2-pyridyl)methylene-2-thiohydantoin

A method is described for the direct spectrophotometric determination of mercury(II) with 5-(6-methyl-2-pyridyl)methylene-2-thiohydantoin. The influence of the different experimental parameters on the formation of the complex were studied and optimum conditions for the determination of mercury were established. The precision of the procedure, expressed in terms of relative standard deviation, was 0.2%. Two different complexes (1:2 and 1:1 cation-reagent stoichiometries) have been detected. The method has been tested on copper amalgam for dental use.     

Synergistic extraction and spectrophotometric determination of copper(II) using 1-(2',4'-dinitro aminophenyl)-4,4,6-trimethyl-1,4-dihydropyrimidine-2-thiol: analysis of alloys, pharmaceuticals and biological samples

A simple and selective spectrophotometric method was developed for the determination of copper(II) with 1-(2',4'-dinitro aminophenyl)-4,4,6-trimethyl-1,4-dihydropyrimidine-2-thiol [2',4'-dinitro APTPT] as a chromogenic reagent. The procedure was based on the synergistic extraction of copper(II) with 2',4'-dinitro APTPT in the presence of 0.5 mol L(-1) pyridine to give green colored ternary complex of a molar ratio 1:2:2 (M:L:Py) in the pH range 8.7-10.5. It exhibits a maximum absorption of colored complex at 445 nm and 645 nm in chloroform against the reagent blank. Beer's law was followed in the concentration range 10-80 μg mL(-1) of copper(II) and optimum range of 20-70 μg mL(-1) the metal as evaluated from Ringbom's plot. The molar absorptivity and Sandell's sensitivity of copper(II)-2',4'-dinitro APTPT-pyridine complex in chloroform are 0.87×10(3) L mol(-1)c m(-1) and 0.072 μg cm(-2), respectively. The interfering effects of various cations and anions were also studied, and use of suitable masking agents enhances the selectivity of the method. The proposed method is rapid, reproducible and successfully applied for the determination of copper(II) in binary and synthetic mixtures, alloys, pharmaceutical formulations, environmental and fertilizer samples. Comparison of the results with those obtained using an atomic absorption spectrophotometer also tested the validity of the method.     

A Practical Synthesis of (S)-(+)-2-(6-methoxyl-2-naphthyl) propionic Acid

a-Arylpropionic acids are an important class of non-steroidal anti-inflammatory agents1,2. The therapeutic efficacy of this class of drugs is well demonstrated by the introduction and extensive use of more than a dozen compounds exemplified by ibuprofen, naproxen, ketoprofen and flurbiprofen etc. However, in recent years the use of enantiomerical pure drugs in chemotherapy is becoming almost mandatory for enhancing specificity of drug action and reducing the toxicity. This awareness led to …     

Simultaneous spectrophotometric determination of Zinc(II) and Nickel(II) with 1-(2-pyridylazo)-2-naphthol

A new procedure for the simultaneous spectrophotometric determination of Zn(II) and Ni(II) with 1-(2-pyridylazo)-2-naphthol as chromogenic reagent has been developed. It is based on resolution of the mixed spectrum over the wavelength range 530–590 nm by applying a least-squares fitting program to standard spectra from each component. The spectra are recorded at an apparent pH of 5.0, provided by an acetate buffer in a mixed 6040 v/v 2-ethoxyethanol/water medium. The relative standard deviations for determination of 13.7 g of Ni and 31.0 g of Zn were 1.9 and 1.0%, respectively (8 replications). The method has been applied to the analysis of iron surfaces coated with a Zn-Ni alloy. The results are compared with those obtained by atomic-absorption spectrophotometry.     

Derivative spectrophotometry in the determination of metal ions with 4-(pyridyl-2-azo)resorcinol (PAR)

Derivative spectrophotometry has been applied for the elimination of the mutual spectral interferences and the analysis of binary, ternary and quaternary mixtures of complexes of microgram amounts of divalent ions of cobalt, copper, lead, manganese, nickel, zinc and iron with 4-(pyridyl-2-azo)resorcinol (PAR) in the range of 0.05-1 microg/ml (0.2-4 microg/ml for lead). The first derivative spectra can be used for the determination of both components in the majority of binary mixtures except of Cu(II) and Co(II) and systems containing Fe(II). The second and the third derivative spectra allow to determine one constituent in some ternary and quaternary mixtures.     

Simultaneous First-Derivative Spectrophotometric Determination of Nickel and Manganese Complexes with 2-(2-Pyridylmethyleneamino)phenol

Abstract

A method is proposed for the simultaneous determination of nickel and manganese by first-derivative spectrophotometry based on their reactions with 2-(2-pyridylmethyleneamino)phenol (PMAP) Schiff base. The method allows the determination of Ni and Mn in the concentration range 0.3–3.0 μg ml^?1 in mixtures with their ten-fold concentration ratio. The method has been applied for Ni and Mn determination in bronzes. To optimize the experimental conditions for spectrophotometric determination of Mn with PMAP stability constants at different pH values have been determined. A critical evaluation of the proposed method was performed by statistical analysis of the experimental data.     

Quinoline-2-aldehyde thiosemicarbazone (QAT) as spectrophotometric reagent for palladium and nickel

A procedure is described for the extractive spectrophotometric determination of nickel and palladium with quinoline-2-aldehyde thiosemicarbazone. At pH 7.5 nickel forms a 1:2 complex which is soluble in chloroform and has an absorption maximum at 460 nm. Palladium forms a 1:2 complex with maximum absorbance at 510 nm which can be extracted into MIBK from 1M HCl. Both complexes are stable and conform to Beer's law. The molar absorptivities for nickel and palladium are 1.58 x 10(4) and 2.6 x 10(3) 1.mole(-1). cm(-1) respectively. The proposed method is suitable for detection and determination of nickel and palladium in the presence of associated metal ions. The results of the analysis of synthetic mixtures and standard samples are reported.     

Spectrophotometric determination of thorium in food using 2-(2,5-disulfonic-4-methoxyphenylazo)-7-(2-hydroxyl-5-carboxylphenylazo)-1,8-dihydroxynaphthalene-3,6-disulfonic acid

A new highly sensitive and selective chromogenic reagent, 2-(2,5-disulfonic-4-methoxyphenylazo)-7-(2-hydroxyl-5-carboxylphenylazo)-1,8-dihydroxynaphthalene-3,6-disulfonic acid (1), was synthesized and applied to the spectrophotometric determination of trace thorium. In 5 mL of a 6 M perchloric acid medium, which greatly increases the selectivity, thorium reacts with 1 to form a 1: 2 green complex, having a sensitive absorption peak at 670 nm. Under optimal conditions, Beer’s law is obeyed over the range from 0 to 0.8 μg/mL Th(IV) and the apparent molar absorptivity is 2.09 × 10⁵ L/mol cm. It is found that, uranium(VI), Ti(IV), heavy rare earths, and most of other common metal ions do not interfere. The method has been tested on the determination of thorium in food samples with satisfactory results. The text was submitted by the authors in English.