N-Acetylacetone-anthranilic acid as a gravimetric reagent for copper(II)

N-Acetylacetone-anthranilic acid has been employed as a reagent for the gravimetric determination of copper(II). The solid copper(II) chelate formed possesses 1:1 metal-ligand stoichiometry and is found to exist as an unsolvated dimer. The complex has a magnetic moment of 1.88 B.M. at 298 K. A non-planar dimeric structure is suggested to explain the observed facts.     

Benzothiazole-2-aldehyde-2-quinolylhydrazone as a reagent for the extractive spectrophotometric determination of copper (II)

Benzothiazole-2-aldehyde-2-quinolylhydrazone (BTAQH) was used for the spectrophotometric determination of trace amounts of copper(II) after the extraction process. Copper(II) reacts with BTAQH at pH 8.3–12.6 to form a water-insoluble 1:2 complex, which can be extracted with many kinds of organic solvent. The extracted species with benzene has an absorption maximum at 523 nm and obeyed Beer's law over the range 0.09 to 0.75 ppm of copper. The molar absorptivity is 7.50 × 10⁴M^?1 cm^?1 at 523 nm. The spectral properties of the copper(II) complexes with some tridentate hydrazones containing benzothiazole ring as a functional group were also discussed.     

Oximidobenzotetronic acid — a sensitive spot test reagent for iron(II), cobalt(II) and copper(II)

Summary Oximidobenzotetronic acid is suggested as a sensitive spot test reagent for iron(II), cobalt(II) and copper(II) in the presence of commonly occuring cations.

---

Zusammenfassung Oximidobenzotetronsäure (3-Ntroso-4-hydroxycumarin) wird als empfindliches Tüpfelreagens zum Nachweis von Fe(II), Co(II) und Cu(II) in Gegenwart anderer Kationen vorgeschlagen.

     

Di-2-Pyridylketoxime,a new reagent for the spectrophotometric determination of iron(II)

Di-2-pyridylketoxime is proposed for the spectrophotometric determination of iron(II). The complex is stable and exhibits an absorption maximum at 534 nm in an alkaline citrate medium. Beer's law is obeyed and the molar absorptivity is 1.5·10³. Large amounts of copper and nickel can be tolerated. The method is simple, convenient and reproducible.     

A new reagent for the spectrophotometric determination of magnesium (II): Khimduchlorophosphonazo-I

Summary The colour reaction of magnesium(II) with Khimduchlorophosphonazo-I (KCPA-I) has been studied spectrophotometrically with a view to develop a procedure for the determination of exchangeable magnesium in acidic soils.The optimum acidities are pH 8.78–9.90. The absorption maximum and molar absorptivity of the coloured complex are 580 nm and 1.85 · 10⁴ l · mol^–1 · cm^–1, respectively. The colour intensity is stable for 4 h and is found to obey Beer's law within the concentration range of 0–20 g per 25 ml. The method is simple and reliable (standard deviation 0.8–1.2%). It has been applied to the determination of exchangeable magnesium.

---

Neues Reagens für die spektralphotometrische Bestimmung von Magnesium (II): Khimduchlorophosphonazo-I

Zusammenfassung Die Farbreaktion von Magnesium mit Khimduchlorophosphonazo-I wurde im Hinblick auf die Entwicklung eines entsprechenden Analysenverfahrens untersucht. Der optimale pH-Wert liegt im Bereich von 8,78–9,90. Das Absorptionsmaximum liegt bei 580 nm, der molare Extinktionskoeffizient beträgt 1,85 · 10⁴l · mol^–1 · cm^–1. Die Färbung bleibt 4 h lang stabil und befolgt das Beersche Gesetz von 0 bis 20 g/25 ml. Das Verfahren ist einfach und zuverlässig (Standardabweichung 0,8–1,2%) und wurde zur Bestimmung von austauschbarem Magnesium in sauren Böden angewendet.

     

Diformylhydrazine as analytical reagent for spectrophotometric determination of iron(II) and iron(III)

The bidentate ligand diformylhydrazine (OHC-HN-NH-CHO), DFH, combines with iron(II) and iron(III) in alkaline media in the pH range 7.3-9.3 to form an intensely colored red-purple iron(III) complex with an absorption maximum at 470 nm. Beer's law is obeyed for iron concentrations from 0.25 to 13 microg mL(-1). The molar absorptivity was in the range 0.3258x10(4)-0.3351x10(4) L mol(-1) cm(-1) and Sandell's sensitivity was found to be 0.0168 microg cm(-2). The method has been applied to the determination of iron in industrial waste, ground water, and pharmaceutical samples.     

The polarographic and chronopotentiometric investigation of the copper(II)-ethylenedithioldiacetic acid system

The electrode process of the Cu(II)-ethylenedithioldiacetic acid chelatereduction occurs in two one-electron reduction steps. The reversibility of the first polarographic wave was confirmed by microcoulometry at constant potential. The second wave was found to be quasi-reversible unless the chelate forming agent is present in great excess. The kinetic parameters of these electrode processes were evaluated from the Koutecký and Matsuda-Ayabe theories. The value of activation energy at E=0 vs. NHE, was also found.The chronopotentiometric investigations of the same system gave resultswhich are in good agreement with those obtained polarographically.     

Electrochemical reduction of copper(II) galacturonate

The complexes formed in the interaction between copper(II) anda-andβ-galacturonic acid, in the pH range 2.5–11.0, have been investigated by means of d.c. polarography and cyclic voltammetry. Witha-galacturonic acid, no complex is formed with copper up to pH 6. Between pH 6 and about 9.5, a complex is formed in solution. Above pH 9.5, the complex appears to break up releasing the ligand. In the case of β-galacturanic acid, no complex is formed until pH 3.5, and persists in solution up to a pH of about 9.5. A second complex forms above pH 6.9 and co-exists with the first complex up to pH 9.5. The complexes formed with both forms of galacturonic acid were studied and the stability constant of the coppera-galacturonate determined.     

Triangular silver nanoplates as a spectrophotometric reagent for the determination of mercury(II)

The applicability of triangular silver nanoplates (TNPs) as a spectrophotometric reagent for the determination of mercury(II) in an aqueous solution was estimated. The method is based on the oxidation of TNPs with a mean edge length of 52 nm and thickness of 4 nm by mercury(II) ions, which is accompanied by a decrease in the surface plasmon resonance of nanoparticles. The effect of reaction time, pH of solution, and TNP concentration on the sensitivity of mercury(II) determination was studied. The limit of mercury(II) detection under the selected conditions was 0.022 μg/mL.     

Electrochemical synthesis of copper(II) carboxylates

A number of copper(II) carboxylates have been synthesized by anodic oxidation of copper. The reactions were found to proceed with current efficiencies of 0.95 to 1.00 eq./Faraday. Reaction products have been characterized by infrared spectral studies and analysis of copper.     

Spectrophotometric total protein assay with copper(II)-neocuproine reagent in alkaline medium

Total protein assay was made using copper(II)–neocuproine (Nc) reagent in alkaline medium (with the help of a hydroxide-carbonate-tartarate solution) after 30 min incubation at 40 °C. The absorbance of the reduction product, Cu(I)–Nc complex, was recorded at 450 nm against a reagent blank. The absorptivity of the developed method for bovine serum albumin (BSA) was 0.023 l mg⁻¹ cm⁻¹, greater than that of Lowry assay (0.0098), and much greater than that of Cu(II)–bicinchoninic acid (BCA) assay (0.00077). The linear range of the developed method (8–100 mg l⁻¹ BSA) was as wide as that of Lowry, and much wider than that of BCA (200–1000 mg l⁻¹ BSA) assay. The sensitivity of the method was greater than those of Cu-based assays (biuret, Lowry, and BCA) with a LOD of 1 mg l⁻¹ BSA. The within-run and between-run precisions as RSD were 0.73 and 1.01%, respectively. The selectivity of the proposed method for protein was much higher than those of dye-binding and Lowry assays: Most common interferents to other protein assays such as tris, ethanolamine, deoxycholate, CsCl, citrate, and triton X-100 were tolerated at 100-fold concentrations in the analysis of 10 mg l⁻¹ BSA, while the tolerance limits for other interferents, e.g., (NH₄)₂SO₄ and acetylsalicylic acid (50-fold), SDS (25-fold), and glycerol (20-fold) were at acceptable levels. The redox reaction of Cu(II)–Nc as an outer-sphere electron transfer agent with the peptide bond and with four amino acid residues (cystine, cysteine, tryptophan, and tyrosine) was kinetically more favourable than that of Cu(II) alone in the biuret assay. Since the reduction product of Cu(II) with protein, i.e., Cu(I), was coordinatively saturated with Nc in the stable Cu(Nc)₂⁺ chelate, re-oxidation of the formed Cu(I) with Fenton-like reactions was not possible, thereby preventing a loss of chromophore. After conventional protein extraction, precipitation, and redissolution procedures, the protein contents of the minced meat (veal and turkey), sardine, various milk products, and egg white were analyzed with the proposed and Lowry methods, and the results correlated appreciably (r = 0.98). The method was validated by Kjeldahl analyses of the tested samples; the data sets of complex samples assayed by Cu(II)–Nc and Lowry correlated to the findings of Kjeldahl yielded correlation coefficients r = 0.96 and 0.97, respectively, with slopes being close to 1. Interferences of glucose and thiol compounds at relatively low concentrations could be compensated for by selecting a lower alkaline pH (i.e., pH 10) at a cost of slightly reduced sensitivity and adding an identical amount of interferent to the reagent blank, respectively, since the absorbances due to BSA and interferent were additive. Thus a novel spectrophotometric method for total protein assay using a stable reagent and chromophore, which was simple, rapid, sensitive, flexible, and relatively selective, was developed, and applied to a variety of food products.     

A simple and selective flow-injection spectrophotometric determination of copper(II) by using acetylsalicylhydroxamic acid

A new simple, and rapid flow-injection spectrophotometric method is developed for the determination of trace amounts of Cu(II) by using a new chromogenic reagent acetylsalicylhydroxamic acid (AcSHA). The method is based on the formation of colored Cu(II)-(AcSHA)₂ complex. The optimum conditions for the chromogenic reaction of Cu(II) with AcSHA is studied and the colored (green) complex is selectively monitored at λ_max 700 nm. With the reagent carrier solvent (dimethylsulfoxide (DMSO) and acetate buffer, pH 4.2) flow-rate of 1 ml min⁻¹, a detection limit (2S) of 1 μg l⁻¹ Cu(II) was obtained at a sampling rate of 80 sample h⁻¹. The calibration graph was linear in the Cu(II) concentration range 5-120 μg l⁻¹. The relative standard deviation (n=10) was 0.64% for a sample containing 60 μg l⁻¹ Cu(II). The detailed study of various interferences confirmed the high selectivity of the developed method. The method was successfully applied to determine trace amounts of copper(II) in river and seawater samples. The accuracy of the method was demonstrated by the analysis of standard reference materials C12X3500 and C14XHS 50.     

Furoin thiosemicarbazone as an analytical reagent for nickel(II), palladium(II) and copper(II)

Furoin thiosemicarbazone (FTS) reacts with Ni(II), Pd(II) and Cu(II) in aqueous medium, giving yellow solutions at pH 9, 6 and 3 respectively. The complexes have absorption maxima at 360 nm for Ni(II) and Pd(II) and 355 nm for Cu(II). At these wavelengths the reagent absorbance is negligible. The molar absorptivities are 1.54 x 10(4) [Ni(FTS)(2)], 1.98 x 10(4) [Pd(FTS)(2)] and 1.45 x 10(4) 1.mole(-1).cm(-1) (CuFTS). Beer's law is valid up to 4, 5 and 3 ppm for Ni, Pd and Cu respectively. The apparent instability constant of the Ni-FTS system is found to be 6.5 x 10(-11), of the Cu-FTS system 7.1 x 10(-7) and of the Pd-FTS system 3 x 10(-12) at the recommended pH values. The effect of various ions is reported.     

Spectrophotometric determination of ascorbic acid using copper(II)-neocuproine reagent in beverages and pharmaceuticals

The proposed method for ascorbic acid (Vitamin C) (AA) determination is based on the oxidation of AA to dehydroascorbic acid with a Cu(II)-2,9-dimethyl-1,10-phenanthroline (neocuproine (Nc)) reagent in ammonium acetate-containing medium at pH 7, where the absorbance of the formed bis(Nc)-copper(I) chelate is measured at 450 nm. This chelate was formed immediately and the apparent molar absorptivity for AA was found to be 1.60 × 10⁴ dm³ mol⁻¹ cm⁻¹. Beer's law was obeyed between 8.0 × 10⁻⁶ and 8.0 × 10⁻⁵ M concentration range. The relative standard deviation for 90 μg AA was 3%. The Cu(II)-Nc reagent is a milder and therefore more selective oxidant than the conventional Fe(III)-1,10-phenanthroline (phen) reagent used for the same assay. This feature makes the proposed method superior for real samples such as fruit juices containing weak reductants such as citrate, oxalate and tartarate that otherwise produce positive errors in the Fe(III)-phen method when equilibrium is achieved. The developed method was applied to a number of commercial fruit juices, pharmaceutical preparations containing Vitamin C, and red wine. The meta-bisulfite content of wine was removed with an anion exchanger at pH 3 prior to analysis, and a difference extractive–spectrophotometric method of AA assay in wine was developed so as to suppress the interferences caused by wine anthocyanins and polyphenols. The findings of the developed method for fruit juices and pharmaceuticals were also statistically compared with those of HPLC so as to establish it as a reliable novel method.     

Structure-stability relationship of copper(II)-indol carboxylic acid derivative complexes from spectrophotometric,thermogravimetric and potentiometric studies

Some copper(II) complexes of N-methyl indol carboxylic acid derivatives have been isolated and characterized. These complexes were subjected to elemental and thermogravimetric analyses together with UV, visible and IR spectral studies. Based on these physicochemical studies, the suggested formula for the complexes obtained is CuL₂ where L = N-methyl indol carboxylic acid derivatives L₁-₄.Thermogravimetric analyses of the isolated complexes have already indicated different modes of interaction between the ligands and the central copper(II) metal ions. UV, visible and IR spectral studies have indicated that coordination of the ligands to the central metal ion is via carboxylic-, hydroxyl- and/or nitrogen-containing groups.The stability constants of some of these metal chelates were determined from potentiometric measurements and found to be in the order Cu(L₃)₂ < Cu(L₂)₂ < Cu(L₄)₂, which essentially depends on the acid dissociation constants of the ligands, determined under the same conditions.     

Investigation of ketoconazole copper(II) and cobalt(II) complexes and their spectrophotometric applications

Ketoconazole, as a ligand, reacts quantitatively with copper(II) and cobalt(II) to form blue-colored, stable complexes in dichloromethane. These complexes can be spectrophotometrically measured at 720 and 612.5 nm in the case of Cu(II) or Co(II), respectively. Different factors affecting the reaction such as pH, reagent concentration, solvent effect, and time were studied. By using Job's method of continuous variation, the stoichiometry of the reaction was found to be in the ratio of 1:2, metal:drug, with Cu(II) and Co(II). The stability of the complexes formed was also studied. The reaction products were isolated for further investigation. The complexes have apparent molar absorptivities of 35.36 +/- 1.95 and 59.62 +/- 1.87 for Cu(II) and Co(II), respectively. Suggested procedures based on the stoichiometric reaction were successfully applied to the analysis of the pure drug and its pharmaceutical formulations. The validity of the procedures was further ascertained by the method of standard additions. The developed method was found to be simple, accurate, and precise when compared with the official method of the British Pharmacopoeia.     

New reagent for spectrophotometric determination of salicylic acid

In 6M hydrochloric acid solution, salicylic acid reacts with pentachloronitrosyliridate [Ir(NO)Cl(5)](-) to form a new 1:1 complex giving two absorption maxima at 369 and 446 nm with molar absorptivities both of 1.1 x 10(4) l.mole(-1) cm(-). The reaction is second order with apparent energy, E(a), of 16.8 kJ/mole. At constant temperature, the apparent rate constant k increases to a maximum when the concentration of hydrogen ion is decreased to 4-5M and the concentration of chloride ion is kept at approximately 6M. The mechanism of the reaction is also discussed. In alkaline solution, the absorption maxima shift to 381 and 506 nm with molar absorptivities of 6.0 x 10(3) and 2.4 x 10(4) l.mole(-1) cm(-1), respectively. Salicylic acid can be determined spectrophotometrically with high sensitivity and precision. Benzoic and boric acids do not interfere.     

N-cyclopropylation of indoles and cyclic amides with copper(II) reagent

Copper-mediated coupling reactions of cyclopropylboronic acid with indoles and cyclic amides are described. The process utilizes catalytic or stoichiometric amounts of copper(II) acetate, DMAP, and NaHMDS at 95 degrees C under an atmosphere containing oxygen. A variety of functional groups remain intact throughout the reaction.