Indirect spectrophotometric determination of chromium(VI)

A new simple and sensitive spectrophotometric method for the determination of chromium(VI) is established. It relies upon the oxidation of iron(II) with the titled ion, in acidic medium, to form iron(III) which is complexed with tiron to form a stable blue color with maximum absorption at 650 nm. Adherence to Beer's law is observed in the range 10–100 μg of chromium(VI) per 25 ml, with a molar absorptivity of 5.6 × 10³ liters mol^?1 cm^?1, sensitivity index of 0.0093 μg cm^?1, relative error of ?5.0 to +0.3%, and relative standard deviation of 0.3–4.0%, depending on the concentration level. Furthermore, the reaction needs neither temperature control nor an extraction step.     

Hydrazine sulphate as reagent for titrimetric determination of vanadium(V) and chromium(VI)

Conditions have been developed for the direct titration of vanadium(V) and chromium(VI) with hydrazine sulphate, barium diphenylaminesulphonate being used as indicator and osmium tetroxide as catalyst.     

Method for the determination of chromium (VI) as chromium (VI)-dibenzyidithiocarbamate

Dibenzyldithiocarbamic acid (DBDC) exhibits the ability to speciate between chromium(VI) and chromium(III), since only the chromium(VI) will form complexes with DBDC. The complex is then extracted into an organic solvent and assayed using an ultraviolet-visible (UV-VIS) spectrophotometer at 498.8 nm. Using 250 ml of aqueous sample detection limits less than 1 ng/ml are possible, while the linear range extends to 500 gmg/ml when working at 498.8 nm. Oxidation of the chromium(III) to chromium (VI) using cerium (IV) enables the determination of total chromium and subsequently the chromium (III) in solution. Evaluation of the method with a standard reference material produced only 4.81 part per thousand error in the determination of chromium(VI).     

Flow injection direct spectrophotometric assay for the speciation of trace chromium(III) and chromium(VI) using chromotropic acid as chromogenic reagent

A new rapid and sensitive FI assay is reported for the simultaneous direct spectrophotometric determination of trace Cr(VI) and Cr(III) in real samples. The method is based upon the reaction of Cr(VI) with chromotropic acid (CA) in highly acidic medium to form a water-soluble complex (λ_max = 370 nm). Cr(III) reacts with CA only after its on-line oxidation to Cr(VI) by alkaline KIO₄. The determination of each chromium species in the sample was achieved by absorbance differences. The calibration curves were linear over the range 3-4000 μg l⁻¹ and 30-1200 μg l⁻¹ for Cr(VI) and Cr(III), respectively, while the precision close to the quantitation limit was satisfactory in both cases (s_r = 3.0% for Cr(VI) and 4.0% for Cr(III) (n = 10) at 10 and 50 μg l⁻¹ level, respectively). The method developed proved to be adequately selective and sensitive (c_L = 1 and 10 μg l⁻¹ for Cr(VI) and Cr(III), respectively). The application of the method to the analysis of water samples (tap and mineral water) gave accurate results based on recovery studies (93-106%). Analytical results of real sample analysis were in good agreement with certified values.     

Extraction and spectrophotometric determination of molybdenum(VI) with Malachite Green and p-chloromandelic acid

Molybdenum(VI) reacts with p-chloromandelic acid to form a complex extractable into chlorobenzene with Malachite Green, from aqueous solution at pH 2.0-4.0 at room temperature, and can then be determined indirectly by measuring the absorbance of the Malachite Green in the extract, at 630 nm. The calibation graph is linear for molybdenum over the range 0.26-10.0 x 10(-6)M (0.10-4.0 mug); the apparent molar absorptivity is 1.06 x 10(5) l.mole(-1).cm(-1). The method has been applied to the determination of molybdenum in mild steels with satisfactory results.     

Ion flotation—spectrophotometric determination of traces of chromium(VI)

Ion flotation is used to concentrate chromium(VI) in the range 3–70μg l^-1 from 14 samples. The chromium(III)—diphenylcarbazone complex formed by reaction with diphenylcarbazide is floated efficiently with sodium lauryl sulfate, and the subsided foam is measured spectrophotometrically after simple dilution. Continuous flotation methods at solution flow rates of 2, 3 and 4 l h^-1 are discussed.     

Propericiazine as a reagent for the spectrophotometric determination of ruthenium(III)

Propericiazine forms an orange-red species with ruthenium(III) immediately in 6–8 M phosphoric or hydrochloric acid or 4.5–5.5 M sulphuric acid. The absorption maximum is at 511 nm and the molar absorptivity is 1.1 × 10⁴ 1 mol^?1 cm^?1. Beer's Law is obeyed over the range 0.2–9.4 mg 1^?1 (optimum range 0.5–9.0 mg 1^?1). Interferences are described. The method is used to determine ruthenium in synthetic zinc–magnesium alloy and uranium alloy (fuel) solutions.     

Diphenylcarbazone as a sensitive reagent for the spectrophotometric determination of iridium(IV)

Summary The blue iridium(IV)-diphenylcarbazone complex, formed by heating the solutions in boiling water bath for 45 minutes, having an absorption maximum at 550 nm with maximum molar absorptivity of 1.90·10⁴l·cm^–1·mole^–1 (within 1.5 %) is recommended for the spectrophotometric determination of 40–240g iridium(IV) in 25–60 % ethanol medium. The complex formed in solutions at pH 3.5–7.0, after formation, is stable within the pH range 2.5 to 9.2. The effect of foreign ions has been investigated.

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Zusammenfassung Der blaue Iridium(IV)-diphenylcarbazon-Komplex entsteht beim Erwärmen der beiden Lösungen im siedenden Wasserbad für 45 Min. Er hat ein Absorptionsmaximum bei 550 nm und eine molare Extinktion von 1,90 × 10⁴ l·cm^–1·mole^–1. Diese Farbreaktion wird zur spektrophotometrischen Bestimmung von 40–240g Ir(IV) in 25-bis 60%igem Äthanol empfohlen. Der bei pH 3,5–7,0 entstandene Komplex ist zwischen pH 2,5 und 9,2 beständig. Der Einfluß von Fremdionen wurde untersucht.

     

Spectrophotometric determination of Chromium(VI) using cyclam as a reagent

A simple, rapid, sensitive, and inexpensive method for spectrophotometric determination of chromium(VI), based on the absorbance of its complex with 1,4,8,11-tetraazacyclotetradecane (cyclam) is presented. The complex showed a molar absorbtivity of 1.5?×?10⁴?L?mol^?1?cm^?1 at 379?nm. Under optimum experimental conditions, a pH of 4.5 and 1.960?×?10³?mg?L^?1 cyclam were selected, and all measurements were performed 10?min after mixing. Major cations and anions did not show any interference; Beer's law was applicable in the concentration range 0.2–20?mg?L^?1 with a detection limit of 0.001?mg?L^?1. The standard deviation in the determination is ±0.5?mg?L^?1 for a 15.0?mg?L^?1 solution (n?=?7). The described method provides a simple and reliable means for determination of Cr(VI) in real samples.     

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.     

Arsenazo III as a spectrophotometric reagent for determination of lead

Arsenazo III is proposed as a spectrophotometric reagent for the determination of lead. The complex formation begins at pH > 2 and is greatest at pH 4-6. The molar absorptivity of the complex has a mean value of 2.8 x 10(4) 1.mole(-1).cm(-1) at 600 nm and remains nearly constant in the pH range 4-8. The ionic species taking part in the reaction are studied and the equilibrium constants for the different possible reactions are calculated. According to the values obtained, the reaction of PbOH(+) with H(5)L(3-) is predominant. The reaction studied is applied for the determination of micro amounts of lead in technical aluminium.     

Benzoylacetanilide as a spectrophotometric reagent for iron(III)

Benzoylacetanilide (BAA) forms violet colored complex Fe(BAA)₃ with Fe(III) in 60% alcohol with λmax at 540 nm. The stability constant (log K) and free energy of formation of the complex at 20 °C are log K = 7.8 ± 0.1 and ΔF = −10.53 kcal/mole, respectively. The molar adsorptivity, sensitivity, effect of diverse ions in spectrophotometric determination of iron have also been investigated.     

Indirect spectrophotometric determination of traces of antimony(III) based on its oxidation by chromium(VI) and reaction of chromium(VI) with diphenylcarbazide

An indirect method for the determination of antimony(III) is described. Antimony(III) is oxidized to antimony(V) by chromium(VI) and the excess of chromium(VI) is then determined spectrophotometrically with diphenylcarbazide. Optimal conditions were established for both the determination of antimony(III) and the elimination or reduction of interferences. Antimony(III) can be determined quickly and easily in the range 0.05–5 mg l^?1; the relative standard deviation is 2% for 1.0 mg l^?1 antimony(III). The method is applicable to marine sediments and geothermal waters.     

Propionyl promazine phosphate as a new reagent for the spectrophotometric determination of rhodium(III)

Summary PPP forms an orange-red coloured complex with rhodium(III) at room temperature (27°) in the presence of sodium acetate-hydrochloric acid buffer of pH 1.0–3.0 containing copper(II) and ascorbic acid. The complex exhibits absorption maximum at 470 nm. Beer's law is valid over the rhodium concentration range 0.1–18g/ml. Sandell's sensitivity of the reaction is 1.8·10^–3 g Rh/cm² and the molar extinction coefficient is 5.68×10³ l·mol^–1cm^–1 at 470 nm. The composition of the complex is 11 and the apparent stability constant of the complex at pH 2.5 and 27° has the logK value of 4.0. The proposed method has been used for the determination of rhodium in thermocouple wires and in synthetic mixtures containing palladium, ruthenium, osmium, uranium or iridium.

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Propionylpromazinphosphat (PPP), ein neues Reagens für die spektrophotometrische Bestimmung von Rhodium(III)

Zusammenfassung PPP bildet mit Rh(III) bei Zimmertemperatur (27°) in Gegenwart von Natriumacetat-Salzsäure (pH 1,0–3,0), Cu(II) und Ascorbinsäure eine orange-rote Komplexverbindung mit einem Absorptionsmaximum bei 470 nm. Das Beersche Gesetz gilt für Konzentrationen von 0,1 bis 18g/ml. Die Empfindlichkeit nach Sandell beträgt 1,8×10^–3 g Rh/cm²; der molare Extinktionskoeffizient bei 470 nm ist 5,68×10³ l·mol^–1·cm^–1. Die Zusammensetzung der Komplexverbindung entspricht dem Verhältnis 11, die scheinbare Stabilitätskonstante bei pH 2,5 und 27° entspricht log K=4,0. Das vorgeschlagene Verfahren diente zur Rh-Bestimmung in Thermoelementdraht sowie in synthetischen Gemischen aus Pd, Ru, Os, U und Ir.

     

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.     

Ion-chromatographic determination of chromium (VI)

Summary A simple ion-chromatographic method has been developed for the selective determination of chromium (VI) using UV-photometric detection. The anion exchanger was based on a matrix of a 2-hydroxyethyl-methacrylate copolymer; the mobile phase consisted of phosphate buffer and sodium perchlorate. The relative standard deviation was 2.26%. Application was made to waste waters of the metallurgical industry.