Speciation of Cr(III) and Cr(VI) by reversed phase high-performance liquid chromatography using UV-detection

Summary A method for the simultaneous determination of Cr(III) and Cr(VI) in water samples is described. The different reaction products of Cr(III) and Cr(VI) species with ammonium pyrrolidinedithiocarbamate (APDC) are extracted with ethyl acetate and determined by reversed phase HPLC using UV-detection. The procedure is optimized and its detection limit accordingly improved as compared to literature data. The detection limits achieved are 2.4 g/l for Cr(III) and 2.1 g/l for Cr(VI) and the calibration curves are linear between 5 g/l and 5000 g/l. For the speciation of Cr, APDC was demonstrated to be more suitable as chelating agent than sodium diethyldithiocarbamate (NaDDC). The procedure was applied to the determination of both Cr species in galvanic waste waters and its accuracy was approved by comparing the results (at the 100 g/l level) with those of a photometric determination of Cr(VI) species.Dedicated to Professor Dr. Wilhelm Fresenius 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.     

Spectrofluorimetric flow-injection determination of cerium in carbon and low alloy steels

Cerium can be determined spectrofluorimetrically (_em 350 nm, _ex 260 nm) based on the relatively intense native fluorescence of the cerium(III) aquo-ion. The main potential interference in the analysis of steel from iron(III), cerium(IV) and chromium(VI) are removed by use of a carrier solution containing 2.5% w/v hydroxylammonium chloride. The slight residual interference from iron(II) can be corrected by a matrix matching factor linearly related to the amount of iron present. The calibration graphs are linear over the range 0–7 g ml^–1 based on 250 l injection volumes. The sampling rate was 30 h^–1. The relative standard deviation was 2.0% (n=5) at 3 g ml^–1 cerium. The system has been applied to the determination of cerium in carbon or low alloy steels.     

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.     

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.

     

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.     

Effect of Surfactants on the Immobilization of 4-(2-Pyridylazo)resorcinol on Silochroms

The effect of cationic surfactants (cetyltrimethylammonium bromide, cetylpyridinium bromide, and tetrabutylammonium perchlorate) and a nonionic surfactant (OP-7) on the conditions of the immobilization of 4-(2-pyridylazo)resorcinol (PAR) on three types of silica gel (Silochrom S-120 (200–350 m), Silochrom S-120 (315–500 m), and Silochrom S-80 (200–350 m)) was studied. It was found that OP-7 does not affect the adsorption of surfactants. The effect of cationic surfactants increases in the order tetrabutylammonium perchlorate < cetyltrimethylammonium bromide < cetylpyridinium bromide. The adsorption activity of silica gels increases in the order Silochrom S-120 (315–500 m) < Silochrom S-80 (200–350 m) < Silochrom S-120 (200–350 m). Cetylpyridinium bromide provides full immobilization of PAR on silica gel Silochrom S-120 (200–350 m) in the pH range 2–9.     

Flow injection analysis at μl/min flow rates

The characteristics of knitted open tube (KOT) figure eight reactors and coil reactors at l/min flow rates were compared using plate height (H) calculations and peak height measurements. Peak broadening independent of flow rate was seen for the figure eight KOT but not the coil at flow rates of 150–300 l/min. Below 150 /min, the plate height values of both reactors were inversely proportional to flow rate. It was concluded that a 0.5-m KOT figure eight reactor is the most effective way to introduce delay time for a 1 1 injection size and tubing of 0.3 mm I.D. Enhancement of peak height response was particularly pronounced at flow rates less than 100 l/min.     

Lead determinations in human bone by particle induced X-ray emission (PIXE) and graphite furnace atomic absorption spectrometry (GFAAS)

Chronic lead (Pb) intoxication has been linked to Alzheimer's disease (AD). Lead, like many heavy elements, tends to accumulate in bone. PIXE is a powerful analytical tool which permits the determination of Pb at the g/g level without requiring sample digestion. GFAAS is one of the most sensitive methods for the determination of Pb and is capable of determining ng/g levels in solution. For bone analyses by GFAAS, sample dissolution and a matrix modifier are required. Rib bone samples were analyzed for Pb by PIXE and GFAAS. IAEA Animal Bone (H-5) was used as a secondary standard for Pb with both methods to ensure accuracy. The range of Pb concentrations in human rib bone was 1.4–11.5 g/g for the trabecular surface by PIXE, 1.3–45 g/g for the cortical surface by PIXE, and 1.54–11.75 g/g for whole bone by GFAAS. No significant difference (p>0.05) was found for AD versus control for either surface or for whole bone.     

Determination of metoprolol in human plasma by column switching high-performance liquid chromatography

Summary Retention characteristics of metoprolol have been studied in reversed phase mode on RP2, RP8 and CN columns. The plots of retention time as a function of the acetonitrile content and of the ionic strength of the mobile phase permitted the choice of the best conditions to separate metoprolol from plasma components by switching of these three types of columns.Human plasma (0.5–1 ml) diluted with water is first injected on a RP2 column (25–40 m particle diameter, prepared by dry packing) and rinsed with water. The sample is then back eluted with acetonitrile-0.022 M acetate buffer (7525, v:v) and switched to a CN column (10 cm long, 5 m particle diameter). The heart cut of the eluate is selected and loaded on a RP8 analytical column (25 cm long, 5 m particle diameter) with acetonitrile-0.088 M acetate buffer (7525, v:v) as mobile phase.Auto-sampler and switching valves are actuated automatically by a computing integrator based on a fixed time schedule. The duration of one cycle is about 30 min, but the last analytical step is about 15 min and represents the time interval between two injections. Metoprolol, its alpha-hydroxy metabolite and the internal standard are detected by fluorescence (_ex= 225 nm; _em > 320 nm).Presented at the 14th International Symposium on Chromatography London, September, 1982     

Vergleichende Untersuchungen der Konzentrationen von Dimethylarsons?ure, As(III) und As(V) in Boden- und Luftstaubproben

Zusammenfassung Es wird ein Analysenverfahren vorgestellt, das die Abtrennung und Bestimmung von Dimethylarsonsäure (DMAS) und As(III) aus Festproben erlaubt.DMAS wird aus der Festsubstanz verflüchtigt und mit einem mikrowelleninduzierten Plasma und optischer Emissionsspektrometrie nachgewiesen. As(III) wird mittels eines Extraktionsverfahrens aus der Festsubstanz abgetrennt und atomabsorptionsspektrometrisch (AAS) nachgewiesen. Die Bestimmung von Gesamtarsen erfolgt nach Druckaufschluß des Probenmaterials ebenfalls atomabsorptionsspektrometrisch. Die Analysenverfahren werden auf die Untersuchung von Boden- und Luftstaubproben angewendet. Die Gehalte der einzelnen As-Spezies, die in verschiedenen Bodenproben bestimmt werden, zeigen eine starke Abhängigkeit von der Bodentiefe. Die Gehalte der einzelnen Spezies in den Luftstaubproben sind stark abhängig vom Standort und von den Witterungsbedingungen. Die Gesamtarsengehalte in den Bodenproben schwankten zwischen 1 und 22 g As/g Boden; in Luftstaub lagen die Werte zwischen 12 und 61,4 g As/g Luftstaub. Die maximale Konzentration an DMAS in Bodenproben lag bei 11,2 ng DMAS/g Boden. Die Gehalte an As(III) schwankten zwischen 0,3 und 10,5 g As(III)/g Boden und 3 und 30,3 g As(III)/g Luftstaub.

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Comparative investigations of the concentrations of dimethylarsonic acid, As(III) and As(V) in soil and airborne dust samples

Summary An analytical method is described for the separation and determination of dimethylarsonic acid (DMAA) and As(III) in solid samples. DMAA is volatilized from the solid material and detected with a microwave induced plasma and optical emission spectroscopy. As(III) is extracted from the solid material and detected by atomic absorption spectroscopy. After decomposition under pressure, the total arsenic content is also detected by atomic absorption spectroscopy. These analytical methods are used for the investigation of soil and airborne aerosol samples. It has been found that the contents of the different arsenic species, analyzed in different soil samples depends strongly on the depth of the soil whereas in airborne aerosol samples, the contents of the different As-species is strongly dependent on the sampling site and on the meteorological conditions. The total arsenic concentrations varied from 1 to 22 g As/g soil in soil samples and from 12 to 61.4 g As/g aerosol in airborne aerosol samples. The maximum concentration of DMAA found in soil samples was 11.2 ng DMAA/g soil. The concentrations of As (III) varied from 0.3 to 10.5 g As(III)/g soil in soil samples and from 3 to 30.3 g As(III)/g aerosol in airborne aerosol samples.

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Herrn Prof. Dr. K. H. Lieser zum 65. Geburtstag gewidmet     

Indole derivatives

The behavior of some 3-nitrovinyl indoles in their reactions with nitrogen-containing nucleophilic reagents is examined. It is shown that hydroxylamine, phenylhydrazine, hydrazine, and semicarbazide react with 3--nitrovinyl indole to give the corresponding oxime, phenylhydrazone, azine, and semicarbazone of indole-3-aldehyde, possibly by decomposition of intermediates formed by the addition of the nucleophilic reagents to the nitrovinyl indole. 3--Nitropropenyl indole and N-methyl-3--nitrovinyl indole react similarly. Only the addition products of phenylhydrazine with N-acetyl-3-nitrovinyl indole and N-acetyl-3--nitropropenyl indole are stable. The reaction conditions and constants of the compounds prepared are given, and explanations are offered for the results obtained.For part XXXV, see [14].     

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).     

Determination of Ultratrace Levels of Mercury in Three SRMs by Combustion RNAA

A radiochemical neutron activation analysis (RNAA) combustion method coupled with a neutron exposure normalization technique was used to determine low g/kg mercury levels in three National Institute of Standards and Technology (NIST) Standard Reference Materials (SRMs). Two coals (sub-bituminous and bituminous) and a diet material were analyzed. The results obtained provided recommended values of approximately 5 g/kg for SRM 1548a Typical Diet, 24 g/kg for SRM 1635 Trace Elements in Coal (sub-bituminous), and 100 g/kg for SRM 1632b Trace Elements in Coal (bituminous).     

Laboratory studies on the adsorption behavior of americium

With increasing global nuclear activities, there is a growing interest in understanding the migration behavior of transuranic elements in the terrestrial environment. The laboratory investigations on the adsorption behavior of AM(III) (10^–7M) in aqueous solutions showed that there was not adsorption of Am(III) on glass or polyethylene vials from aqueous solutions at pH<3. The rate of adsorption was found to be inversely related to the (H⁺) in the pH range 4–7. It was also found to be strongly influenced by stirring/shaking as well as by the presence of particulate matter in the aqueous phase. The presence of particulate matter (>0.6 m) in the aqueous solutions significantly inhibits the adsorption rate. Attempts to fit the kinetic data (collected on filtered [particle size >0.6 m] or unfiltered distilled water at pH 6) to the reversible or irreversible first order rate equation did not successfully indicate the complexity of the adsorption process. The presence of 20mg/liter of humic acid at pH 6.3 completely inhibits the adsorption of Am on glass surfaces.     

Bestimmung von Borspuren in Metallen durch Emissionsspektrometrie mit ICP-Anregung nach Abtrennung als Bors?ure-Ester

Zusammenfassung Zur Bestimmung von Borgehalten im ng/g- und unteren g/g-Bereich in Metallen (Mo, W, Zr, Al, Fe, Co) wurden Verbundverfahren ausgearbeitet, bei denen Bor nach geeignetem Probenaufschluß durch Destillation des Borsäuremethylesters oder durch Ausschütteln als 2-Ethyl-1,3-hexandiol-Komplex abgetrennt und emissionsspektrometrisch mit ICP-Anregung (ICP-OES) bestimmt wird. Mit einer neu entwickelten Kreislaufdestillationsapparatur aus Quarzglas lassen sich Bormengen zwischen 0,02 und 20 g innerhalb von 15 min aus schwefeloder schwefel-phosphorsauren Lösungen von Metallen (Einwaage1g) quantitativ als Methylester abtrennen und in wenigen Millilitern alkalischer Lösung konzentrieren. Das Verfahren ist für alle Metalle anzuwenden, für die man zum Lösen keine HF benötigt. Die Ethylhexandiol-Extraktion wurde für die Abtrennung von 0,02 bis 1 g Bor optimiert, wobei besonders die Matrices Mo, Fe, Zr und Al untersucht wurden. Die ICPOES ist für die Bestimmung von Gehalten an abgetrenntem Bor von 20 ng/ml geeignet. Je nach Matrix und Höhe der Einwaage können somit Nachweisgrenzen von 0,02 g/g erreicht werden.

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Determination of traces of boron in metals by emission spectrometry with ICP after separation as boric acid ester

Summary Procedures for the determination of boron in the ng/g- and low g/g-range in metals (e.g. Mo, W, Zr, Al, Fe, Co) by emission spectrometry (OES) with inductively coupled hf-plasma (ICP) excitation have been investigated. The procedures involve the suitable dissolution of the samples and the separation of boron either by distillation of boric acid methyl ester with a new circulation distillation apparatus or by liquid extraction of the 2-ethyl-1,3-hexanediol complex. By distillation 0.02 to 20 g of boron are separated within 15 min from sulphuric or sulphuric-phosphoric acid solutions ( 1g of sample) and are concentrated in a few milliliters of NaOH. This separation is applicable to all metals which do not require hydrofluoric acid for dissolution. The ethylhexanediol extraction has been optimized for 0.02 to 1 g of boron in solutions of Mo, Fe, Zr, and Al. With ICP-OES concentrations of separated boron of 20 ng/ml can be determined, corresponding to limits of detection down to 0.02 g/g, depending on matrix and sample weight.

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Herrn Professor Dr. W. Fresenius zum 70. Geburtstag gewidmet     

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.     

Atomic-absorption spectrophotometric determination of ultramicro amounts of selenium(IV) and total selenium in sulphuric acid

Summary Ultramicro amounts of selenium in sulphuric acid are determined by a new atomic absorption spectrophotometric method. Selenium(IV) is directly determined ater extraction into toluene with an aromatic o-diamine and addition of nickel(II) prior to atomization; the determination of total selenium (0, IV and VI) needs a treatment of the sample with selected oxidizing and reducing agents.In the studied samples, total selenium (0.003–0.022 g of Se in 1 ml sulphuric acid) is present only in the tetravalent state. The detection limit of the method is 0.003 g of selenium.

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Atomabsorptions-spektralphotometrische Bestimmung von Ultramikromengen Selen(IV) und Gesamtselen in Schwefelsäure

Zusammenfassung Selen(IV) kann direkt bestimmt werden nach Toluolextraktion der mit einem aromatischen o-Diamin behandelten Lösung und Zusatz von Nickel(II). Die Bestimmung von Gesamtselen (0, IV, VI) erfordert eine Vorbehandlung mit Perchlor- bzw. Salpetersäure und Wasserstoffperoxid. Die Nachweisgrenze des Verfahrens beträgt 0,003 g Se. In den untersuchten Proben war das Gesamtselen (0,003–0,022 g/ml) nur als Se(IV) vorhanden.