Determination of Cr(VI) and Cr(III) by Using Activated Carbon-Atomic Absorption Spectrometry

A method for the separation and preconcentration of Cr(III) and Cr(VI) on activated carbon in presence of diethyldithiocarbamate as a complexing reagent was optimized. The method makes it possible to achieve 200- to 500-fold Cr(VI) concentrating depending on the initial volume of the solution to be analysed and the final volume eluted. The Cr(VI) concentration in the background solution determined with RSD 30% was equal to 1.5 g L. The limit of Cr(VI) determination was equal to 0.9 g L.     

Simultaneous determination of chromium (III) and chromium (VI) by reversed-phase ion-pair HPLC with chromium-specific detection

A method for the simultaneous determination of Cr(III) and Cr(VI) with reversed-phase ion-pair HPLC employing chromium-specific detection by flame atomic absorption spectrometry (FAAS) and inductively-coupled plasma mass spectrometry (ICP-MS) is presented. Experimental parameters of the chromatographic separation, such as concentration of the ion-pairing reagent, pH and polarity of the mobile phase have been optimized for two different ion-pairing reagents, tetrabutylammonium phosphate (TBA) and tetraethylammonium nitrate (TEA). Best chromatographic conditions have been obtained with a polymer-based reversed-phase column (Hamilton PRP1) and mobile phases containing either TBA (1 mmol/l) in methanol-water (60:40, v/v) or TEA (2 mmol/l) in water at a pH between 3 and 4. With FAAS the detection limits (3) have been found to be 24 g/l for Cr(III) and 40 g/l for Cr(VI). A detection limit of 0.3 g/l Cr(3) for both chromium species has been obtained when ICP-MS has been used for detection. The method has been applied to analyze tap- and groundwater and to investigate the behaviour of Cr(III) and Cr(VI) in spiked tap-water, as well as to analyze aqueous extracts of coal fly ash (NIST SRM 1633a) and of an ash from a wood treatment company.     

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.

     

New specific methods for the detection of chromium(VI) and vanadium(V) using primaquin

Summary New specific methods have been developed for the detection of chromium(VI) and of vanadium(V), based on the formation of a purple color with primaquin in concentrated sulfuric acid solution. The identification limits and dilution limits have been determined to be 0.05g, 11 000 000 for chromium(VI) and 0.1g, 1500 000 for vanadium(V) respectively.

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Neue spezifische Methoden zum Nachweis von Cr(VI) und V(V) mit Primachin

Zusammenfassung Die neu ausgearbeiteten Methoden sind spezifisch und beruhen auf der Bildung einer Purpur-Färbung mit Primachin in konz. Schwefelsäure. Die Nachweisgrenzen und Verdünnungsgrenzen betragen 0,05g bzw. 11 000 000 für Cr(VI) und 0,1g bzw. 1500 000 für V(V).

     

2-(α-Pyridyl)-thioquinaldinamide (PTQA)-A novel fluorimetric reagent in inorganic trace analysis. I: The nonextractive,nonquenching fluorescent method for the determination of chromium(VI)

A direct fluorimetric method for determining Cr(VI) in aqueous solutions is described. The nonfluorescent reagent 2-(-pyridyl)-thioquinaldinamide (PTQA) and Cr(VI) interact to produce an intensely fluorescent species [_ex(max) 360 nm; _em(max) 500 nm] showing constant and maximum fluorescence intensity in slightly acidic media (0.18N–1.08N H₂SO₄). The fluorescence attains its maximum value within 5 min and remains unchanged for 24 h. The system obeys Beer's law from 2 ng/ml to 0.8 g/ml of Cr(VI). Over sixty cations, anions and complexing agents are without any effect on the fluorimetric determination of 0.1 g/ml of Cr(VI). The method has been tested with synthetic mixtures, steels, solutions containing both Cr(III) and Cr(VI), and environmental samples.     

Controlled-potential coulometric studies on fluoride and sulphate complexes of neptunium (VI)

Fluoride and sulphate complexing of Np(VI) has been studied by controlled-potential coulometry at a constant ionic strength. The values of ₁ ^* and ₂ ^* for fluoride complexes were found to be 9.4 and 8.9, respectively, at an ionic strength =0.5. At an ionic strength =1.0, ₁ ^* and ₂ ^* obtained were 6.6 and 10.5, respectively. Sulphate complexing of Np(VI) was studied only at an ionic strength =0.5. The value of ₁ ^* obtained was 5.6.     

Trace uranium analysis of water from the south-west coastal region of India

Water samples collected from various sources along the south-west coastal region of India have been analyzed for trace uranium concentration. Fission track registration technique with the Dry method has been used for the analysis. Uranium concentration was found to vary from 0.28±0.01 g/l to 2.71±0.41 g/l and was higher in sea water than in well, river and tap water, respectively.     

Simultaneous determination of chromium(VI) and chromium(III) by flame atomic absorption spectrometry with a chelating ion-exchange flow injection system

Summary Simultaneous Determination of Chromium(VI) and Chromium(III) by Flame Atomic Absorption Spectrometry with a Chelating Ion-Exchange Flow Injection System A simple method is described for the simultaneous determination of chromium(VI) and chromium(III) in a flow injection system comprising chelating ion-exchange and flame atomic absorption spectrometry. Sampling rates for 2001 and 1 ml sample volumes were 120 and 60 h^–1 (240 and 120 speciations per hour), respectively. Typical relative standard deviations were 0.52% for Cr(VI) (0.50g ml^–1 and 0.67% for Cr(III) (0.10,g ml^–1) and the corresponding limits of detection were 85 ng ml^–1, and 16 ng ml^–1, respectively.On leave from University of Belgrade.     

Simultaneous determination of zinc and mercury with 5,10,15,20-tetrakis(3-chloro-4-sulfophenyl)porphine by differential rate kinetics and flow injection analysis

A rapid and sensitive differential rate kinetic method for the simultaneous and sequential determination of zinc and mercury with 5,10,15,20-tetrakis-(3-chloro-4-sulfophenyl)porphine (m-Cl-TPPS₄) has been based on flow injection spectrophotometry. By proper stopped-flow of the merging zone, the metalloporphyrin complexes of zinc and mercury were simultaneously determined at the maximum absorbance wavelength of 425.7 nm with the proportional equation. The relative standard deviations for 1.0 g/ml zinc and 5.0 g/ml mercury with 100 l sampling volume were 0.43% and 0.62%, respectively, for 8 parallel determinations. The calibration graphs were linear over the concentration range 0–3.0 g Zn/ml and 0–12.0 g Hg/ml. The method has been applied to the analysis of synthetic water samples with satisfactory recovery.     

Über die katalytische Wirkung einiger Elemente in einer Landolt-Reaktion auf “Brom-Grundlage”; Ultramikrobestimmung von Molybdän(VI)

Zusammenfassung Die Landolt-Reaktion auf Bromgrundlage des Systems Wasserstoffperoxid—Bromid—Ascorbinsäure—Tolidin wird durch Mo(VI), Fe(III), Cu(II), V(V) und W(VI) katalysiert. Auf dieser Grundlage läßt sich Mo(VI) mit Hilfe der Simultankomparationsmethode bei 65° C in einem Konzentrationsbereich von 1 bis 10g/5 ml und bei 50° C in einem Konzentrationsbereich von 0,1 bis 1g/5 ml mit einem relativen Fehler von ±0.5% bestimmen.

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Summary The Landolt reaction on a bromine basis of the system hydrogen peroxide-bromide-ascorbic acid-tolidine is catalyzed by Mo(VI), Fe(III), Cu(II), V(V), and W(VI). On this basis, Mo(VI) can be determined with the aid of the simultaneous comparation method at 65° C in a concentration range from 1 to 10g/5 ml and at 50° C in a concentration range from 0.1 to 1g/5 ml with a relative error of ±0.5%.

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Résumé La «réaction de Landolt, avec brome» du système eau oxygénée—bromure—acide ascorbique—tolidine, est catalysée par Mo-VI, Fe-III, Cu-II, V-V et W-VT. On peut donc doser Mo-VI par la méthode de comparaison simultanée à 65° C dans un domaine de concentration de 1 à 10g/5 ml et à 50° C de 0,1 à 1g/5 ml avec une erreur relative de ±0,5%.

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Die vorliegende Arbeit sollte Herrn Prof. Dr.E. Schulek zu seinem 70. Geburtstag gewidmet werden. Noch ehe die Publikation möglich war, ist Herr Prof.Schulek am 14. Oktober 1964 leider gestorben.     

A new spot test reagent for chromium(VI), vanadium(V), and hexacyanoferrate(III) ions: the schiff base from 4,4′-methylenedianiline and 4-dimethylaminobenzaldehyde

Summary A new Schiff base, bis(4-dimethylaminobenzylidine)4,4-methylenedianiline (I) has been prepared by reacting 4-dimethylaminoben-zaldehyde with 4,4-methylenedianiline. A 1% solution ofI in conc. sulphuric acid gives a deep red or blood red colour with Cr(VI), and V(V), and a deep rose red colour with [Fe(CN)₆]^3-. The limits of detection and dilution are 0.7 g, 171,000 for Cr(VI); 5 g, 110,000 for V(V); and 7 g, 17,100 for [Fe(CN)₆]^3-. Cr(III), V(IV), and [Fe(CN)₆]^4- do not interfere. The effects of common anions and cations are reported.

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Zusammenfassung Durch Umsetzung von 4-Dimethylaminobenzaldehyd mit 4,4-Methylen-dianilin wurde eine neue Schiffsche Base hergestellt, deren 1%ige Lösung in konz. Schwefelsäure eine tiefrote oder blutrote Farbe mit Cr(VI) und V(V), eine tiefrosa Farbe mit [Fe(CN)₆]^3– gibt. Die Nachweisgrenzen bzw. die Grenzkonzentrationen betragen: 0,7 g, 171000 für Cr(VI), 5 g, 110000 für V(V) und 7 g, 17100 für [Fe(CN)]₆ ^3–. Cr(III), V(IV) und [Fe(CN)₆]^4– stören nicht. Der Einfluß gängiger Anionen und Kationen wird angegeben.

     

Flame atomic absorption spectrometric determination of cadmium and copper in biological reference materials using on-line sorbent extraction preconcentration

Summary Cadmium and copper at the g/g to ng/g level in plant and animal tissue reference materials, and at the g/l level in urine were determined by flame atomic absorption spectrometry using on-line sorbent extraction preconcentration based on flow injection techniques. Bonded silica reversed phase sorbent with octadecyl functional groups (RP-C 18), packed in a 100 l column, was used to collect the diethylammonium-N,N-diethyldithiocarbamate (DDTC) complex formed on-line in the sample digests at low pH. Methanol was used to elute the analyte chelates directly into the nebulizer-burner system of the spectrometer. Small air segments introduced before and after elution prevented the eluent from mixing with the sample solution and increased the sensitivity. A sampling frequency of 85/h could be obtained with a sample loading time of 30 s at a flow rate of 4.0 ml/min. The enrichment factor for both elements was 20 and the enhancement factors, including the effect of the organic solvent and with the flow spoiler removed, were 126 and 114 for cadmium and copper, respectively. The detection limits (3) were 0.15 g/l for cadmium and 0.2 g/l for copper. The precision was 2.3% and 1.4% r.s.d. for 10 g/l Cd and 45 g/l Cu, respectively (n=11). Results for the determination of cadmium and copper in various biological reference materials were typically in good agreement with certified values. Low recoveries were observed, however, for cadmium in samples containing high levels of copper and/or iron, such as bovine liver.On leave from Flow Injection Analysis Research Center, Institute of Applied Ecology, Academia Sinica, Shenyang, China     

Improved spectrophotometric determination of uranium(VI) with 4-(2-pyridylazo)resorcinol in the presence of benzyldimethylstearyltrimethylammonium chloride

An improved spectrophotometric determination of uranium(VI) is proposed using 4-(2-pyridylazo)resorcinol(PAR) in the presence of benzyldimethylstearyltrimethylammonium chloride(BSTAC) as a cationic surfactant. The calibration graph is linear in the range of 0.3–60 g/10 ml uranium(VI), measuring the absorbance at 550 nm. The reproducibility for 19.0 g/10 ml uranium(VI) is 0.57%. The third-derivative method using the third-derivative distance (d³A/d³) among ₁ 530 nm, ₃ 594 nm and ₂ 565 nm was also investigated.     

Adsorption voltammetric techniques for the determination of uranium(VI) with 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone as complex forming reagent

Uranium (VI) can be determined by adsorptive voltammetric techniques, as its chloranilic acid complex, over a wide concentration range. Differential pulse polarography is useful for quantification of uranium between 0.1 and 1.5 mg/l; for the range from 10 to 500 g/l differential pulse voltammetry and for ultra-trace analysis between 0.024 and 40 g/l adsorptive stripping voltammetry are preferred. The standard deviation for the 3-detection limit of 24 ng/l uranium was found to be 8%. In the trace analysis of metals in aquatic environmental systems by adsorptive stripping voltammetry it is normally necessary to decompose polluted water samples by UV irradiation or microwave digestion. The advantage of the developed method is the fact that no sample pretreatment is necessary.Dedicated to Professor R. Geyer on the occasion of his 80th birthday     

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.     

Grenzkonzentration und Erfassungsgrenze quantitativer Analysenmethoden. Berechnung dieser Kennzahlen für (spektral-)photometrische Verfahren

Zusammenfassung Es wird vorgeschlagen, den unteren Anwendungsbereich quantitativer Methoden ebenso wie in der qualitativen Mikroanalyse durch die Begriffe Grenzkonzentration und Erfassungsgrenze zu kennzeichnen. Durch die Ableitung dieser Werte nach mathematisch-statistischen Regeln erhalten Grenzkonzentration und Erfassungsgrenze den Charakter objektiver Kennzahlen. Für photometrische und spektralphotometrische Methoden werden Gleichungen zur Berechnung der Grenzkonzentration ing/ml und in Prozent der Probe, sowie der Erfassungsgrenze ing Substanz angegeben. Berechnungsgrundlagen sind die Streuung der Blindwerte, der molare Extinktionskoeffizient oder der Sandellsche Empfindlichkeitsindex und andere analytische Parameter.

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Summary It is suggested that the lower application region of quantitative methods, just as in the case of qualitative microanalyses, be characterized by the concepts limiting concentration and detection limit. These values acquire the character of objective coefficients when they are derived in accord with mathematical-statistical laws. Equations for calculating the limiting concentration ing/ml and in % of the sample, as well as the detection limit ing of the material, are given for photometric and spectrophotometric methods. The bases for the calculation are the dispersion of the blank values, the molar extinction coefficient, or the Sandell sensitivity index and other analytical parameters.

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Herrn Professor Dr.Hans Lieb aus Anlaß seines 80. Geburtstages gewidmet.     

Solid phase radioimmunoassay of triiodothyronine (T3) using antibody coupled carboxymethylcellulose powder

The paper describes a solid-phase radioimmunoassay for triiodothyronine (T₃) using antibody coupled to carboxymethylcellulose powder. The free carboxylic acid groups of cellulose are covalently coupled to the amino groups of the antibody using 1-ethyl-3-(3-dimethylamino-propyl) carbodiimide hydrochloride. Immobilized antibody thus prepared was used in a solid-phase radioimmunoassay of T₃. The assay has a sensitivity of 0.18 g/l, and a range of 0.18–4 g/l. Satisfactory correlation was obtained when this assay was compared with a T₃ assay based on dextran coated charcoal separation system (Y=0.95X+0.15 g/L; r=0.98).     

Uranium and thorium determination in Brazilian coals by epithermal neutron activation analysis

An experimental technique has been developed to determine impurities in coal. Uranium was determined by counting the²³⁹Np 106.1 keV -ray with a LEPS detector and thorium by counting the²³³Pa 311.8 keV -ray with a Ge(Li) detector. Seventeen coal samples were analyzed with an average precision of 3% and a quantitative determination limit of 0.153 g/g for uranium and 0.078 g/g for thorium. The technique allows determinations of up to twenty elements besides U and Th and can be applied in routine analysis.     

New Molybdenum(V) Complexes Prepared by the Oxidation of Dinuclear Quadruply-Bonded Molybdenum(II) Monothiocarboxylates

Oxidation of molybdenum(II) thiopivalate and thiobenzoate in the presence of -picoline or pyridine results in the formation of dinuclear molybdenum(V) complexes of the general formulae [Mo₂O₂(-O)₂(-SO₄)L₄] with L = -picoline or pyridine and [Mo₂O₂(-O)(-S)(-SO₄)L₄] with L = -picoline. As determined by X-ray structure analysis, two complexes with -picoline differ in their bridging cores: In one complex, two Mo atoms are doubly bridged through two oxygen atoms; in the other, one Mo atom is doubly bridged through oxygen and sulfur atoms. However, they both crystallize together. The product is solvated with -picoline and water molecules. Molybdenum atoms exhibit distorted octahedral coordinations. The same complexes were prepared also through direct reactions of [Mo₂O₃(O₂CCH₃)₄] with thiopivalic and thiobenzoic acid in the presence of -picoline or pyridine. The appearance of the oxo-oxygens and sulfido-sulfur as well as sulfato ligand is explained by the molybdenum-catalyzed oxidation of thiocarboxylates.