Spectrophotometric determination of vanadium(IV) in the presence of vanadium(V) using Br-PADAP

In the present paper, a simple and sensitive method is proposed for vanadium(IV) determination in the presence of vanadium(V). This is based on the oxidation of vanadium(IV) present in the sample to vanadium(V) by addition of iron(III) cation, followed by a complexation reaction of iron(II) with the spectrophotometric reagent 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Br-PADAP). The iron(II) reacts with Br-PADAP immediately, forming a stable complex with a large molar absorptivity. The vanadium(IV) determination is possible, with a calibration sensitivity of 0.549 g ml^–1, for an analytical curve of 18.8 ng ml^–1 to 2.40 g ml^–1, molar absorptivity of 2.80 × 10⁴ 1 mole^–1 cm^–1 and a detection limit of 5.5 ng ml^–1. Selectivity was increased with the use of EDTA as a masking agent. The proposed method was applied for the vanadium(IV) determination in the presence of several amounts of vanadium(V). The results revealed that 200 g of vanadium(V) do not interfere with determination of 5.00 g of vanadium(IV). The precision and the accuracy obtained were satisfactory (R. S. D.<2%).     

Extraction and spectrophotometric determination of uranium(VI) withN-phenylcinnamohydroxamic acid

Uranium(VI) reacts withN-phenylcinnamohydroxamic acid to form an orange-yellow complex in the pH range 5.5–8.5. The orange-yellow complex, having the composition of 12 (metal:ligand), is quantitatively extractable into ethyl acetate. The spectrum of the complex exhibits a maximum absorption at 400 nm with a molar absorptivity of 6500 M^–1·cm^–1. The coloured system obeys Beer's law in the concentration range 2–40g·ml^–1 of uranium(VI). The photometric sensitivity of the colour reaction is 0.037 g·cm^–2 of uranium(VI). Most of the common ions do not interfere and the method has been found to be simple, precise, and free from the rigid control of experimental conditions. The method has been applied to the determination of uranium in synthetic matrices and potable water.     

Study of Cr(VI)-2-oximinodimedone dithiosemicarbazone reaction and simultaneous determination of Cr(VI) and Fe(III)

Summary 2-Oximinodimedone dithiosemicarbazone reacts with Cr(VI) in strongly acid medium. The orange colour obtained has been used to propose a spectrophotometric method of Cr(VI) determination in the concentration range 0.40–9.5g ml^–1 (=5600 mole^–1-cm^–1 at 485 nm). The stoichiometry of the reaction is 32 (reagentCr(VI)) which is in accordance with the oxidation reaction of the reagent by Cr(VI). The method has been applied to the determination of Cr(VI) and Fe(III) in ceramic materials.

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Eine Studie zur Cr(VI)-2-oximinodimedondithiosemicarbazon-Reaktion und die simultane Bestimmung von Cr(VI) und Fe(III)

Zusammenfassung 2-Oximinodimedonedithiosemicarbazon reagiert in stark saurem Milieu mit Cr(VI). Die orange Farbe kann im Konzentrationsbereich von 0.4–9,5g/ml zur spektrophotometrischen Cr(VI)-Bestimmung verwendet werden (=5600 1 mol^–1cm^–1bei 485 nm). Die Stöchiometrie der Reaktion ist 32 (Reagens: Cr(VI)) und entspricht der Oxidation des Reagens durch Cr(VI). Die Methode wurde zur Bestimmung von Cr(VI) und Fe(III) in keramischen Materialien eingesetzt.

     

Extractive spectrophotometric determination of dioxouranium(VI) with the sodium salt of hexamethyleneiminecarbodithioate

The optimum conditions for the extractive spectrophotometric determination of dioxouranium(VI) with hexamethyleneiminecarbodithioate(HMICdt) have been established. Dioxouranium(VI) reacts with this ligand at pH 4.5 to form a yellowish-orange uncharged 12 metal-ligand complex which can be extracted by chloroform. The calibration graph was linear in the range of 1–20 g ml^–1 of dioxouranium(VI) at 335 nm. The molar absorptivity of the extracted species is 5.952×10³ l mol^–1 cm^–1 with Sandell's sensitivity of 0.04 g cm^–2. The average of 10 determinations of dioxouranium was 49.75 g for the samples containing 50 g of U(VI) and the variation from the mean at 95% confidence limit was 49.75±0.5955.     

Spectrophotometric determination of microgram amounts of chromium(VI) and total chromium in waste water

Summary A spectrophotometric method has been developed for the determination of chromium in waste water with 5-Br-PADAP (2-(5-brorno-2-pyridylazo)-5-diethylaminophenol). Chromium(III) forms a blue-purple complex at pH 4.7 upon heating. The color is very stable and is highly sensitive for chromium. At 600 nm it obeys Beer's law in the concentration range of 0–15g of Cr(III) per 25 ml. The sensitivity and molar absorptivity of the reaction are 0.00065g of Cr(III) per cm² and 7.93×10⁴1 · mole^–1 · cm^–1, respectively. The continuous variation and molar ratio methods indicate that chromium forms 12 complex with the ligand.

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Spektrophotometrische Bestimmung von Mikrogramm-Mengen Chrom(VI) und Gesamt-Mengen Chrom in Abwasser

Zusammenfassung Eine spectrophotometrische Methode zur Bestimmung von Chrom in Abwasser mit 5-Br-PADAP wurde ausgearbeitet. Chrom(III) bildet mit 5-Br-PADAP bei pH 4,7 durch Erhitzen einen blaupurpurnen Komplex. Die Farbe ist sehr beständig. Bei 600 nm entspricht die Färbung dem Beerschen Gesetz zwischen 0 und 15g Cr(III)/25 ml. Die Empfindlichkeit der Reaktion beträgt 0,00065g Cr(III)/cm² und die molare Absorption 7.93×10⁴ 1 · mol^–1 · cm^–1. Die Untersuchung nach Job ergab für den Komplex das Molverhältnis Cr:Reagens=12.

     

Spectrophotometric determination of mercury with 5,10,15,20-tetrakis(3-chloro-4-sulfophenyl)porphine by flow injection analysis

5,10,15,20-tetrakis(3-chloro-4-sulfophenyl)porphine (m-Cl-TPPS₄) was synthesized and used for the Spectrophotometric determination of mercury by flow injection analysis. A pseudo-first-order reaction kinetic mechanism was proposed with a rate constant of 0.8 min^–1 for Hg(II) withm-Cl-TPPS₄ in the presence of 8-hydroxyquinoline in a medium of 1.0M acetic acid and sodium acetate buffer solution (pH 6.22). In the optimum conditions of reaction temperature (85 ° C), stopped-flow time (60 s) and sampling volume (100 l), the method's relative standard deviation was 0.82% (n = 12) at 5.0 g ml^–1 mercury, with a linear range of 0–12.0 g ml^–1 and an analytical frequency of 60h^–1. The detection limit (3) was 0.025 g ml^–1. Interference studies showed that most metal ions co-existing with Hg²⁺ could be tolerated at 100-fold excess levels, but Zn²⁺, Cu²⁺ and Mn²⁺ needed to be masked. The method has been applied to the analysis of water samples with satisfactory results.     

Simultaneous and sequential determination of chromium(VI) and chromium(III) by unsegmented flow methods

Summary Several different configurations for simultaneous and sequential photometric speciation of Cr(VI) and Cr(III) based on the reversed flow injection analysis and completely continuous modes are proposed in this paper. The determination of these species at theg · ml^–1 level is achieved with sampling frequencies between 30 and 100 h^–1 and an r.s.d. of less than ±1% for simultaneous methods and of less than ±3% for the sequential method. The proposed methods are suitable for chromium speciation in waters. A simulation of the continuous monitoring of Cr(VI) and periodical of Cr(III) in natural and waste waters has been performed. The most frequent interferents in these types of samples have been investigated.

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Simultane und sequentielle Bestimmung von Chrom(VI) und Chrom(III) durch unsegmentierte Durchflußmethoden

Zusammenfassung Verschiedene Arten der simultanen und sequentiellen photometrischen Cr(III)- und Cr(VI)-Bestimmung nach der Technik der reversed-flow Injektionsanalyse werden beschrieben. Die relative Standardabweichung für die Bestimmung dieser Chromspezies im g/ml-Bereich bei einer Probenfrequenz von 30 bis 100 je Stunde beträgt weniger als +1% für die Simultan- und weniger als +3% für die sequentiellen Methoden. Eine simulierte kontinuerliche Überwachung von Chrom(VI) sowie eine periodische von Chrom(III) in natürlichem Wasser und Abwasser wird beschrieben. Die häufigsten Störungen werden diskutiert.

     

Determination of palladium, platinum and gold by first derivative spectrophotometry

Summary The application of first-derivative spectrometry to the simultaneous determination of palladium(II), platinum(IV) and gold(III) is described. Light absorption of stable chlorocomplexes formed in 1 mol/l hydrochloric acid provides the basis of their determinations. A difference in the derivative amplitudes between two first-derivative zero crossing points of one metal A is read, corrected for the contribution of metal B and used for quantitation of metal C. Palladium (0.48–20 g ml^–1), platinum (0.16–24 g ml^–1) and gold (0.32–24 g ml^–1) have been determined with good precision and accuracy without any separations. Results are also presented for the simultaneous determination of the three precious metals in the presence of several major constituents.     

Extraction-spectrophotometric determination of chromium with Nitrotetrazolium Blue

The interaction of Cr(VI) and Nitrotetrazolium Blue has been examined. A 12 NTB (CrO₃Cl)₂ ion-associate is formed and is extractable into 1,2-dichloroethane. The optimum conditions have been established. The molar absorptivity at 260 nm was (8.2 ± 0.06) × 10⁴L mol^–1cm^–1. Beer's law was obeyed in the range 0.01–0.4 g ml^–1 Cr(VI). A sensitive and selective method for determination of micro-quantities of Cr(VI) in soils and steels is suggested.     

Chromogenic reaction of bromopyrogallol red with tri- and hexavalent chromium in the presence of cetyltrimethyl ammonium bromide and its application in Cr speciation

The coordination reactions of bromopyrogallol red (BPR) with tri- and hexavalent chromium in the presence of cetyltrimethylammonium bromide (CTAB) have been studied by absorption spectrometry. Results show that the reactions of Cr(VI) and Cr(III) with BPR in the absence or presence of CTAB have different temperature dependences. The reaction mechanism of Cr(VI) is that Cr(VI) is first reduced by BPR to Cr(III) and then the Cr(III) produced reacts with BPR. Based on the study on the coordination reactions and the effects of surfactants upon them, a simple, rapid, sensitive and accurate method for Cr speciation has been developed. Over the range of 0–8 g Cr(VI) or 0–12g Cr(III) per 25ml final volume, the calibration curve is linear with a detection limit of 3.5 × 10^–7 mol/1 for Cr(VI) or 4.4 × 10^–7 mol/1 for Cr(III).     

Fourth-derivative spectrophotometric determination of neodymium in mixed rare earths with methyl thymol blue and cetylpyridinium chloride

A sensitive and selective method is described for the determination of neodymium in mixed rare earths using fourth-derivative spectrophotometry. The method is based on the absorption spectra of 4f electron transitions of the complex of neodymium with methyl thymol blue and cetylpyridinium chloride. The influence of various instrumental parameters and reaction conditions for maximum colour development are investigated. The calibration curve is linear over the range 0–3.5 g ml^–1 neodymium. The relative standard deviation for determination of 1.4 g ml^–1 neodymium (n = 7) is 1.6%. The detection limit (signal-to-noise ratio = 3) is 0.2 g ml^–1.     

Spectrophotometric determination of ruthenium(III) using diphenylcarbazone

Summary The purple violet ruthenium(III)-diphenylcarbazone complex which is formed at p _h 5–7, and has an absorption maximum at 530 nm with molar absorption coefficient 16.2·10⁴l.cm^–1.mole^–1 is suggested for the estimation of 20–125g ruthenium(III) spectrophotometrically in 30–60% ethanol. The complex is stable over p _h range 3.2–8.4. The limits of interference due to foreign ions have been studied.

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Zusammenfassung Der bei p _h 5 bis7 entstehende Ruthenium(III)-Diphenylcarbazon-Komplex hat ein Absorptionsmaximum bei 530 nm und einen Absorptionskoeffizienten von 16,2·10⁴ l.cm^–1.Mol^–1. Die spektrophotometrische Bestimmung von 20 bis 125g Ruthenium(III) in 30 bis 60%igem Äthanol mit Hilfe dieses zwischen p _h 3,2 und 8,4 beständigen Komplexes wurde vorgeschlagen. Die Störung durch Fremdionen wurde geprüft.

     

Extraction-spectrophotometric determination of uranium(VI) with PAR and N-octylacetamide

A new and simple method for selective spectrophotometric determination of uranium(VI) with 4-(2-pyridylazo)resorcinol (PAR) and N-octylacetamide into benzene over pH 7.0–9.0 is described. The molar absorptivity of the complex with 9 different amides is in the range of (0.40–3.2)·10⁴ 1·mol^–1·cm^–1 at the absorption maximum. Out of these, the most sensitive compound N-octylacetamide (OAA) was chosen for detailed studies in the present investigation. The detection limit of the method is 0.008 g U·ml^–1. The system obeys Beer's law in the range of 0–5 g U·ml^–1. The method is free from interferences of most of the common metal ions except vanadium(V) and copper(II), which are masked by proper masking agents. The composition of the complex is determined by curve-fitting method. The method has been applied for the recovery of the metal from rock samples and synthetic mixtures.     

Polarographisches Verhalten der C2-Halogenkohlenwasserstoffe

Summary Investigations on the polarographic and voltammetric behaviour of organic halogen compounds were carried out in order to obtain information on the redox properties and how to develop determination and detection methods. In this second report the dp-polarographic behaviour of the halogen substituted C₂-compounds has been studied in different supporting electrolytes and in various solvents. The electrode processes are discussed and the possibilities for the polarographic determination of the C₂-halogen hydrocarbons. The detection limit is 0.25 g · ml^–1 and the linear current-concentration relationship is observed up to 25 g · ml^–1. A simple and rapid method is proposed for the dp-polarographic determination of 1,2-dibromoethane in gasoline; the relative standard deviation for 20 g · ml^–1 is ±1.8%.     

Spectrophotometric Determination of Trace Amounts of Chromium with Citrazinic Acid

A sensitive and selective spectrophotometric method for the determination of trace amounts of chromium(VI) is described, based on diazotization and coupling reactions. Chromium(VI) oxidizes hydroxylamine in acetate buffer of pH 4.0 ± 0.5 to nitrite, which then diazotizes p-aminoacetophenone to form diazonium salt. The diazonium salt is then coupled with a new coupling agent, citrazinic acid in an alkaline medium, which gives an azo dye with an absorption maximum at 470 nm, a molar absorptivity of 2.12 × 10⁴L mol^–1cm^–1, and a Sandell's sensitivity of 0.00246 g/cm². The color is stable for 6 h and the system obeys Beer's law in the range 2–15 g chromium(VI) in a final volume of 10 mL. The detection limit of chromium(VI) is 0.04 g/mL. Chromium(III) can be determined after it is oxidized with bromine water in an alkaline medium to chromium(VI). The developed method has been successfully applied to the analysis of chromium in alloy steels, industrial effluents, and pharmaceutical preparations.     

Spectrophotometric and derivative spectrophotometric determination of palladium(II) using pyridopyridazine dithione in the presence of non-ionic surfactant

Pyridopyridazine dithione (PPD) was synthesized as a new sensitive and selective reagent for spectrophotometric and derivative spectrophotometric determination of palladium(II). In aqueous and micellar medium, PPD forms 1:4 complexes having molar absorptivities of 4.68 × 10⁴ and 5.74 × 10⁴lmol^–1 cm^–1 at 570 and 615 nm, respectively. Beer's law was obeyed up to 2.2 and 2.5 g ml^–1 with detection limits of 0.2 and 0.1g ml^–1. The relative standard deviations for 1.23g ml^–1 were 2.6 and 1.3%, in the absence and presence of Triton X-100. In fourth-derivative mode, the regression equation, linear range, detection limit and RSD for 0.075 g ml^–1 wereD ₄ = 4.3C + 1.5 × 10^–3, 0.013 – 0.23 g ml^–1, 3.7 ng ml–1 and 0.78%, respectively. The ionization constants of the reagent and stability constants of the complexes were evaluated. The method is free from interference by most common metal ions and anions. The method was applied for determination of palladium in activated charcoal.     

Determination of fission product ruthenium by isotope dilution mass spectrometry

Isotope dilution mass spectrometry using enriched isotope⁹⁶Ru as a spike was applied to the determination of ruthenium as a fission product. Ruthenium in the solution was oxidized to RuO₄ by Ce/IV/ and separated from coexisting metal elements by distillation. Silica-gel technique was employed to enhance ion current of ruthenium in the mass spectrometric measurement. The lower detection limit was 0.005 g ml^–1 and the relative standard deviations /n=3/ for 1.2 and 0.05 g ml^–1 of ruthenium were 0.2 and 0.5%, respectively.     

Indirect determination of arsenic by flotation spectrophotometry

An indirect method of arsenic determination in the submicrogram range via the determination of molybdenum is presented here. High sensitivity is achieved by combination of the chemical amplification during formation of dodecamolybdoarsenic acid (arsenic: molybdenum ratio 1 12) with multiplication due to the formation of ion-association complexes during flotation-spectrophotometric molybdenum determination with crystal violet (molar ratio 1 2). Thus, the amplification factor relating to arsenic is 24.Dodecamolybdoarsenic acid is formed in a weakly acidic medium and is quantitatively extracted byn-butanol. Back extraction of the heteropoly acid to the aqueous phase and its simultaneous destruction provides the basis for the reaction of released molybdate ions with thiocyanate ions. The molybdenum-thiocyanate complex forms a sparingly soluble ion-association complex with crystal violet which can be floated with toluene on the phase boundary (film flotation). After separation of the aqueous phase the floated molybdenum compound is dissolved in acetone and the resulting free crystal violet ions are subjected to photometric determination at 590 nm as equivalent of the concentration of arsenic. The molar absorptivity of crystal violet is 3.2 · 10⁵1 · mol^–1 · cm^–1. Beer's law is obeyed in a concentration range from 0.01 to 1 g Mo · ml^–1 (0.001–0.1 g As · ml^–1). The resulting detection limit for arsenic is 1 ng · ml^–1.     

Catalytic-fluorimetric determination of EDTA and iron(III) by flow injection analysis

Summary In this paper the authors report on several methods for the direct determination of EDTA and indirect determination of iron(III), based on the inhibition effect of EDTA on the catalytic action of copper (II) on the oxidation of 2,2-dipyridyl ketone hydrazone by hydrogen peroxide and on the decrease of this inhibition effect in the presence of Fe(III), respectively. These methods allow the determination of EDTA in the ranges of 0.4–2.0 g · ml^–1 and 0.2–1.0 g · ml^–1 for the normal and reversed FIA modes, respectively, and of 40–240 ng · ml^–1 for Fe(III) by reversed FIA.

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Katalytisch-fluorimetrische Bestimmung von EDTA und Eisen(III) durch FließinjektionsanalyseInhibitionsmethoden

Zusammenfassung Verfahren zur direkten Bestimmung von EDTA sowie zur indirekten Bestimmung von Eisen(III) werden beschrieben. Sie beruhen auf der Inhibitorwirkung von EDTA auf den katalytischen Effekt von Kupfer(II) bei der Oxidation von 2,2-Dipyridylketonhydrazon mit Wasserstoffperoxid bzw. auf der Schwächung dieser Inhibitorwirkung in Gegenwart von Eisen(III). Es ist mit diesen Methoden möglich, EDTA im Bereich von 0,4–2,0 g/ml (normale FIA) bzw. 0,2–1,0 g/ml (umgekehrte FIA) und Eisen im Bereich von 40–240 ng/ml (umgekehrte FIA) zu bestimmen.

     

Simultaneous Determination of Pioglitazone and Glimepiride by High-Performance Liquid Chromatography

A rapid and accurate HPLC method has been developed for simultaneous determination of pioglitazone and glimepiride. Chromatographic separation of the two pharmaceuticals was performed on a Cosmosil C₁₈ column (150 mm × 4.6 mm, 5 m) with a 45:35:20 (v/v) mixture of 0.01 m triammonium citrate (pH adjusted to 6.95 with orthophosphoric acid), acetonitrile, and methanol as mobile phase, at a flow rate of 1.0 mL min^–1, and detection at 228 nm. Separation was complete in less than 10 min. The method was validated for linearity, accuracy, precision, limit of quantitation, and robustness [1, 2]. Linearity, accuracy, and precision were found to be acceptable over the ranges 2.50–30.00 g mL^–1 for pioglitazone and 0.10–10.00 g mL^–1 for glimepiride.