Evaluation of two new asymmetric derivatives of thiocarbohydrazide as spectrophotometric analytical reagents

The synthesis and analytical properties of 1-(2-pyridylmethylideneamino)-3-(4-hydroxybenzylideneamino)thiourea PHT and 1-(2-pyridylmethylideneamino)-3-(2,4-dihydroxybenzylideneamino)-thiourea PDT have been studied. A spectrophotometric method has been used to determine the protonation constants of the reagents and a spectrophotometric survey of the reactions of various cations with PHT and PDT has been made.     

Derivatives of imidazole as spectrophotometric analytical reagents

Summary Derivatives of Imidazole as Spectrophotometric Analytical Reagents The synthesis, characteristics and metal-ion reactions of three imidazole derivatives, namely 4(5)-D-arabinotetrahydroxybutylimidazoline-2-thione (THBIT), and the oxime (IMALOX) and rhodanine (IMAR) of 4(5)-imidazolecarboxaldehyde, have been studied. IMALOX and IMAR exhibit three pK values in aqueous solution, but THBIT exhibits only one. All the reagents form stable complexes with only a small number of cations and some of them show promise as Spectrophotometric reagents.     

Derivatives of 2-thiohydantoin as spectrophotometric analytical reagents

The synthesis, characteristics, properties and reaction with metallic ions of four pyridine derivatives of 2-thiohydantoin have been studied. 5-(2-Pyridyl)methylene-2-thiohydantoin, 5-(6-methyl-2-pyridyl) methylene-2-thiohydantoin, 5-(di-2-pyridyl)methylene-2-thiohydantoin and 5-[1-(2-pyridyl)-1-methyl] methylene-2-thiohydantoin have been synthesized. The substances exhibit three pK values in aqueous solution and with Ag(I), Au(III), Cu(II), Pd(II) and Zn(II) form complexes with high molar absorptivities.     

Polyurethane foams as solid chromogenic reagents for diffuse reflectance spectroscopy

The chemical reactions of the functional groups in polyurethane foams (PUF) have been studied by use of diffuse reflectance spectroscopy and infrared spectroscopy. It was found that the functional groups are highly reactive towards diazotization by sodium nitrite, azo coupling with 4-nitrophenyldiazonium tetrafluoroborate, oxidation by active chlorine, and condensation with formaldehyde, resulting in the formation of intensely colored products. Heterogeneous chemical reactions of PUF with these compounds in aqueous solution proceed rapidly at room temperature and at low solute concentrations. PUF do not undergo degradation as a result of chemical interactions. The linear response of the Kubelka-Munk function to analyte concentration makes it possible to recommend PUF as solid chromogenic reagents for the determination of nitrite, nitrate, and 1- and 2-naphthols.     

Potential of porphyrins as chromogenic reagents for determining metals in capillary electrophoresis

Although capillary electrophoresis (CE) with photometric detection is a well-established technique for the determination of various inorganic ions, its limited sensitivity has hindered greater development in this area. In this work, we used a mixture of metals consisting of Co(II), Ni(II), Zn(II) and Mn(II) to demonstrate that the sensitivity of CE with ultraviolet–visible (UV–vis) detection can be improved by using chromogenic reagents such as porphyrins. To this end, the metals were reacted with 5,10,15,20-tetrakis(4-sulphophenyl)-porphine dodecahydrate (TPPS₄) to obtain their respective porphyrinato complexes, which were then separated by CE with a citrate buffer and detected at 410 nm. The ensuing electrophoretic method has a limit of detection (LOD) of 3 × 10⁻⁶ M (180 μg L⁻¹) for Co(II), 2 × 10⁻¹⁰ M (0.012 μg L⁻¹) for Ni(II), 4 × 10⁻⁶ M (260 μg L⁻¹) for Zn(II) and 4 × 10⁻⁹ M (0.219 μg L⁻¹) for Mn(II). The method is a highly promising choice for the ultratrace determination of Ni(II) and Mn(II).     

Synthesis and evaluation of some pyridyl-substituted pyrimidines as copper-specific chromogenic reagents

Preparation and metal-ion chromogenic properties of five new 2,4,6-trisubstituted pyrimidines containing pyridyl and methyl or phenyl groups are described. All five exhibit specific chromogenic reactions with copper(I), and two possess suitable characteristics for use as sensitive spectrophotometric copper reagents. The results obtained are also of interest in designing related chromogenic reagents.     

Some new aromatic hydroxylamines as spectrophotometric reagents for vanadium

A comparative study is described of the use of N-benzoyi-o-tolyl-, N-benzoyl-m-tolyl, N-benzoyl-p-tolyl-, N-benzoyl-p-chlorophenyl- and N-phenylacetylphenyl-hydroxylamines, as spectrophotometric reagents for the determination of vanadium, after extraction with chloroform. All the reagents form 1:2 (metal:reagent) complexes in hydrochloric acid media or at pH 4.8–6.0; the dissociation constants of the complexes are of the order of 10^-9 and 10^-8, respectively, except those of N-benzoyl-p-chloro-phenylhydroxylamine which are of the order of 10^-8 in both media. The reactions in hydrochloric acid media are more selective and sensitive than those at pH 4.8–6.0. In presence of alcohol, the wavelengths of maximum absorption decrease. The pK_a values of the hydroxylamines were determined in water and in alcohol-water (1:1) solutions.     

Derivatives of 2-thiohydantoin as spectrophotometric analytical reagents. III

Summary The synthesis, characteristics, properties and reactions with metallic ions of the furfural-, thiophenal-, pyrrolal-, cinnamal-, acetal-, and propional-derivatives of 2-thiohydantoin have been studied. The reagents exhibit twopK values in aqueous solution, and sensitive colour reactions with Pd(II), Cu(I) and (II), Ag(I) and Hg(II). A comparison has been made of the reactivity of all the 2-thiohydantoin derivatives we have studied to date and conclusions have been drawn regarding the influence of the aromatic ring connected to 2-thiohydantoin.

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Derivative des 2-Thiohydantoins als spektrophotometrische Reagenzien. III

Zusammenfassung Die Synthese, die Kennzahlen, die Eigenschaften der Furfural-, Thiophenal-, Pyrrolal-, Acetal-, Propional- sowie des Zimtsäurealdehyd-Derivates des 2-Thiohydantoins und deren Reaktionen mit Metallionen wurden untersucht. In wäßriger Lösung kommen diesen Reagenzien zwei pK-Werte zu. Sie geben empfindliche Farbreaktionen mit Pd(II), Cu(I) und (II), Ag(I) und Hg(II). Die Reaktivität der genannten Derivative wurde untersucht und der Einfluß des mit 2-Thiohydantoin verbundenen aromatischen Ringes daraus ermittelt.

     

Evaluation of some as-triazines and re-evaluation of PDT and ferrozine as reagents for spectrophotometric determination of ruthenium

A sensitive method for the spectrophotometric determination of ruthenium with the ferroinyielding as-triazines has been developed. This method has several advantages; complete reduction of ruthenium species to ruthenium(II) can be achieved by the recommended procedure, which shortens the colour development time, saves the unnecessary use of several-fold excess of the reagent and the molar absorptivity is increased significantly. A few of the new as-triazines together with the commercially available Ferene(R) have been evaluated as ruthenium(II) chromogens. 3-(2-Pyridyl)-5,6-diphenyl-as-triazine (PDT) and ferrozine, a sulphonated derivative of PDT, have been re-evaluated by the new method. It has been observed that the as-triazine acting as a bidentate ligand forms a tris-complex with ruthenium(II) similar to its reaction with iron(II).     

Steric hindrance effects in the use of heterocyclic azodyestuffs as spectrophotometric reagents

The heterocyclic azo dyestuffs 4-(n-methyl-2 -pyridylazo)-resorcinol (where n = 3', 4', 5', 6') have been prepared, and their possible use as spectrophotometric reagents investigated. The dyestuffs are shown to function analogously to the parent ligand 4-(2'-pyridylazo) resorcinol (PAR) in giving red complexes with the ions Co(2+), Ni(2+), Cu(2+), Zn(2+) and UO(2)(2+). Steric effects resulting from the position of the methyl group in the heterocyclic ring are shown to occur in relation both to the spectra of the dyestuffs themselves and to the sensitivity of their reactions with the metal ions.     

Naphthoquinonedioxime derivatives as analytical reagents for the spectrophotometric determination of nickel

Seven naphthoquinonedioxime compounds, including five new compounds. were synthesized and their reactions with nickel, cobalt and iron(II) ions were examined. The metal chelates of these dioximes absorb in the visible region, and the molar absorptivities of the complexes are about 1 · 10⁴ 1 mole^-1 cm^-1 in

aqueous solution. The chelates can be extracted into chloroloform with zephiramine. and the molar absorptivities of the nickel chelates are about 2 · 10⁴ 1 mole^-1 cm^-1. Of the dioximes examined. 1,2-naphthoquinonedioxime-6-sulfonic acid shows the highest sensitivity for nickel; the molar absorptivity of the nickel complex extracted into chloroform with zephiramine is 2.19 · 10⁴ I mole^-1 cm^-1 at 468 nm.     

Flow injection spectrophotometric determination of anionic surfactants using methyl orange as chromogenic reagent

A flow injection(FI) spectrophotometric method for the determination of anionic surfactants was developed on the basis of the competition for the cationic surfactant cetyl pyridine (CP+) chloride between the acidic dye methyl orange (MO) and anionic surfactants. In a pH 5.0 medium the cation of cetyl pyridine (CP+) reacts with dissociated methyl orange (MO-) to form an ion-associate complex, causing a blue shift of lambda(max) from 465 nm for MO- to 358 nm for the CP+ x MO- associate. The MO- in the ion-associate complex can be quantitatively substituted by such anionic surfactants as sodium dodecyl benzene sulfonate (DBS) or sodium lauryl sulfate (LS), leading to an increase in the absorbance measured at 465 nm. This increased absorbance value is proportional to the concentration of anionic surfactants. Various chemical and physical parameters for the FI spectrophotometric method were optimized, and interference-free levels were examined. At the optimized conditions, Beer's law was obeyed in the range 1.4 approximately 25 mg/L sodium DBS for an injected sample volume of 180 microL, and a detection limit of 0.22 mg/L for sodium DBS was achieved at a sampling rate of 90 h(-1). Eleven determinations of a 16 mg/L sodium DBS solution gave a RSD of 0.4%. The proposed method has successfully been applied to the determination of anionic surfactant concentration in waste water and in detergents.     

2-Amino-3-hydroxypyridine as a chromogenic reagent for the spectrophotometric determination of osmium

2-Amino-3-hydroxypyridine forms two coloured complexes, green and violet, with osmium, depending on the pH of the solutions. Based on this reaction, a selective and sensitive spectrophotometric method for the determination of osmium (3-13 ppm in the final solution) alone and in the presence of other metal ions has been developed.     

Flow injection of lithium ion using chromogenic 14-crown-4 derivatives as extraction-spectrophotometric reagents

A system for flow injection of Li+ has been designed, with use of proton-dissociable chromogenic 14-crown-4 derivatives as the extraction-spectrophotometric reagents, and the analytical conditions have been optimised. This flow injection system showed high selectivity for Li+ reflecting the cation-complexing property of the chromogenic crown ethers. The determination of Li+ in the clinical range in blood under a high Na+ background of 130-160 mM was feasible, with a small sample size (50 microliters) and high sampling rate (more than 100 injections per hour), with this method. The proposed extraction-spectrophotometric flow injection system was, therefore, found to be promising for the efficient determination of Li+ in biological samples, such as blood sera, with a high Na+ background.     

Some pyridylazo compounds as sensitive reagents for the spectrophotometric determination of nickel

Six 2-(2-pyridylazo)-5-alkoxyphenol derivatives were synthesized, and their application to the spectrophotometric determination of nickel was studied; 2-(2-pyridylazo)-5-methoxyphenol and the corresponding ethoxyphenol are very sensitive and selective. The molar absorptivity of the nickel chelate of the former is 11.3 × 10⁴ l mol^-1 cm^-1. A solvent extraction procedure for the selective determination of 1–8 μg of nickel is described.     

Two new spectrophotometric reagents for copper

Two ferroin-type compounds are proposed as spectrophotometric reagents for copper(I): 6-methyl-2-pyridylhydrazidine, which forms a yellow complex with lambda(max) 426 nm and molar absorptivity 700 l.mole(-1).mm(-1), and 3-(6-methyl-2-pyridyl)-5,6-diphenyl-1,2,4-triazine, which forms a red-orange complex with (lambda)max 492 nm and molar absorptivity of 955 l.mole(-1).mm(-1). These reagents are specific for copper and the complexes can be extracted into isopentanol for increased sensitivity.     

Prediction of conditions for use of spectrophotometric reagents: p-dimethylaminobenzilidenerhodanine as a spectrophotometric reagent for silver and palladium

A method for theoretical estimation of the detection limits of spectrophotometric reagents is reported. The concentration limits of Beer's law when p-dimethylaminobenzilidenerhodanine is used for determination of silver and palladium are defined on the basis of the stability constants. Conditions for determination of 2-10mug, of Ag per 25ml and 1-5mug of Pd per 25ml with standard deviation 0.03mug per 25 ml are proposed.     

o-Diketonedioxime compounds as analytical reagents for the spectrophotometric determination of nickel

Sixteen dioxime compounds, including six new compounds, were synthesized and their reactions with nickel, cobalt, iron(II, III) and copper ions were examined. The nickel chelates of the glyoxime derivatives show hardly any absorption in the visible region, and are therefore unsuitable as color reagents. The nickel chelates of the benzildioxime derivatives can be extracted into organic solvents and provide a selective color reaction, so that useful extraction-spectrophotometric methods are possible. The metal complexes of quinonedioximes are extracted into some organic solvents, and the complexes have relatively large molar absorptivities in the visible region, but the reagents are not selective. However, the molar absorptivity of the ternary complex, Ni²⁺-reagent-zephiramine, with 1,2-naphthoquinonedioxime-4-sulfonic acid was 2.03·10⁴ at 480 nm, and that of the nickel complex of 9,10-phenanthrenequinonedioxime was 2.49·10⁴at 456 nm. The compositions of the nickel-dioxime complexes were examined spectrophotometrically.     

Spectrophotometric determination of copper in alkaline solutions and evaluation of some hydroxy-substituted 1,10-phenanthrolines as chromogenic reagents

Seven new hydroxy-substituted 1,10-phenanthroline derivatives have been evaluated as chromogenic reagents for the determination of copper in strongly alkaline solution. The most sensitive of these, 2,9-dimethyl-4,7-dihydroxy-1,10-phenanthroline, has proven to be highly effective in a simple, rapid procedure for determining trace amounts of copper in sodium hydroxide, potassium carbonate, sodium phosphate or ammonium hydroxide.     

薄层色谱分离-水合茚三酮可见分光光度法测定食品添加剂中的γ-氨基丁酸

为建立一种以水合茚三酮为显色剂准确定量检测γ-氨基丁酸(γ-aminobutyric acid,GABA)的方法,本文系统研究了显色酸度、显色剂用量、加热温度和时间等显色条件对水合茚三酮与GABA显色反应的影响,并在最优条件下对该方法进行了评价.结果表明,在pH=7.0时,GABA与1.8 g·L-1茚三酮乙醇溶液沸水...