Spectrophotometric determination of microgram amounts of platinum

2-Ethyl-10-[3-(dimethylamino-2-methyl)propyl]phenothiazine hydrochloride (ethylisobutrazine hydrochloride) forms an orange-red complex with platinum(IV) at room temperature (26 ± 2 °C) in hydrochloric acid-sodium acetate buffer medium containing copper(II) ions. The complexation is complete within 10 min. The complex exhibits an absorption maximum at 529 nm with a molar absorptivity of 1.90 × 10⁴ liters mol^?1 cm^?1. Beer's law is obeyed over the concentration range 0.4–7.8 ppm of platinum. A 50-fold molar excess of the chromogenic reagent is necessary for the development of maximum color intensity. Job's method of continuous variation, the molar-ratio method, and the slope-ratio method indicate a 1:1 composition for the complex. The effects of pH, time, temperature, reagent concentration, order of addition of reagents, and interference of various ions are reported. The reagent has also been used successfully for the determination of platinum in minerals and alloys.     

Particle size determination of platinum, palladium and rhodium

Simple and sufficiently accurate equations are suggested for calculating the particle size of most frequently used supported or unsupported platinum metal catalysts from the amount of chemisorbed gas.

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Separation of platinum and palladium with silicone-rubber foam treated with dimethylglyoxime

Open-pore silicone-rubber foam is shown to be a good inert solid support for column separations. Foams treated with dimethylglyoxime were studied for their adsorption of platinum and palladium from solution. The separation of platinum and palladium was achieved in solutions containing as little as 1.0 ppm.     

Enrichment of trace amounts of gold, silver, palladium and platinum by precipitate flotation

Summary An organic precipitant, p-dimethylaminobenzilidenerhodanine (DABR), is used as the gatherer in precipitate flotation to enrich trace amounts of gold, silver, palladium and platinum from acidic media in the presence of surfactants. The DABR dissolved in dimethylformamide (DMF) does not affect the determination of the enriched metals with electrothermal atomic absorption spectrometry. The presence of a 10²- to 10⁴-fold excess of other usual ions does not interfere with the flotation owing to the high selectivity of DABR for the noble metals in acidic media. As little as 1 ng/l of gold in aqueous solution can thus be determined by AAS. The method has been applied to determine the noble metals in various ore samples with satisfactory results.Dedicated to Prof. Kuang Lu Cheng, University of Missouri, Kansas City, USA on the occasion of his 70th birthdayPresented in part at the Third China-Japan Joint Symposium on Analytical Chemistry, Hefei, China, May, 1988     

The reduction and determination of small amounts of rhenium-VII

Summary Investigations on the reduction of rhenium-VII to rhenium-V have been carried out. The use of stannous chloride in hydrochloric acid solution was not found suitable as the basis for the quantitative determination of the element. The most satisfactory reductant was found to be bismuth amalgam in 18N sulphuric acid. A method is outlined for the determination of milligram amounts of rhenium ranging from 0.1 to 10 mg with a standard deviation of ± 0.02 mg, using this as a basis. The procedure, with only slight modification, can be extended to the determination of microgram amounts of the element.Measurement of absorption spectra indicates that in hydrochloric acid solution a complex is formed between the acid and rhenium-V, but that the stabilisation of rhenium-V by oxalic acid does not arise from the formation of a complex.

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Zusammenfassung Untersuchungen über die Reduktion von Rhenium(VII) zu Rhenium(V) wurden durchgeführt. Zinn(II)-chlorid in salzsaurer Lösung bewährt sich für die quantitative Bestimmung des Rheniums nicht. Als bestes Reduktionsmittel erwies sich Wismutamalgam in 18-n Schwefelsäure. Auf dieser Basis wurde ein Verfahren zur Miüigrammbestimmung von Rhenium ausgearbeitet, das im Bereich zwischen 0,1 und 10 mg Abweichungen von ± 0,02 mg zeigt. Mit nur geringen Abänderungen läßt es sieh auch zur Bestimmung von Mikrogrammengen verwenden.Messungen der Absorptionsspektren ergaben, daß sich in salzsaurer Lösung ein Komplex aus Säure und Rhenium(V) bildet, daß aber die Stabilisierung des 5wertigen Rheniums durch Oxalsäure nicht auf der Bildung eines Komplexes beruht.

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Résumé Recherches sur la réduction du rhénium VII en rhénium V. On a établi que la solution de chlorure stanneux dans l'acide chlorhydrique n'est pas un réactif approprié à la détermination quantitative de l'élément. On a montré que le réducteur le plus satisfaisant était l'amalgame de bismuth dans l'acide sulfurique 18 N. Les auteurs esquissent une méthode basée sur l'emploi de ce réactif pour le microdosage du rhénium en quantités variant de 0,1 à 10 mg avec un écart type de ± 0,02 mg. La technique légèrement modifiée peut être étendue au dosage de quantités de l'ordre de grandeur du microgramme.Les mesures de spectres d'absorption montrent qu'en solution d'acide chlorhydrique il se forme un complexe entre l'acide et le rhénium V mais que par contre la stabilisation du rhénium V par l'acide oxalique ne résulte pas de la formation d'un complexe.

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To Professor Dr.Hans Lieb, University of Graz, for his 70th birthday.

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One of us (H. S.) would like to take this opportunity to thank the Department of Chemistry of the Queen's University of Belfast for the facilities granted in carrying out this work.     

New spectrophotometric method for the determination of trace amounts of palladium

Summary A simple, rapid, selective, and sensitive method for the spectrophotometric determination of palladium is developed based on the reaction of Pd(II) with 1-amino-4-hydroxyanthraquinone (AMHA). The reaction is carried out atpH 3.8 in 50% (v/v) ethanol-water medium. The molar absorptivity of the complexed ligand is 1.1 · 10⁴ l mol^–1 cm^–1 at 620 nm. Calibration plots are linear up to 17 µg Pd cm^–3. The optimum concentration range (Ringbom plot) is between 3–14.5 µg cm^–3. The spectral study of the reaction in solutions containing equimolar concentrations or an excess of one component, in thepH range 0.3–6.5, indicate the possible complex transitions that occur in solution. Complete graphical and logarithmic analysis of the absorbance-pH graphs was performed to demonstrate and characterize the complexation equilibria in solution. Under the optimum conditions, palladium can be determined as the noncharged complex Pd(AMHA)₂ in the presence of a large number of foreign ions. Interferences caused by zirconium(IV) could be masked with fluoride ions.

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Eine neue spektrophotometrische Methode für die Bestimmung von Palladium in Spuren

Zusammenfassung Eine einfache, schnelle und empfindliche Methode für die spektrophotometrische Bestimmung von Palladium wurde auf der Basis der Reaktion von Pd(II) mit 1-Amino-4-hydroxyanthrachinon (AMHA) entwickelt. Die Reaktion wird in 50% (v/v) Ethanol/Wasser beipH 3.8 ausgeführt. Die molare Absorption des komplexierten Liganden beträgt 1.1 · 10⁴ l mol^–1 cm^–1 bei 620 nm. Kalibrierungskurven verlaufen bis zu 17 µg Pd cm^–3 linear. Der optimale Konzentrationsbereich (Ringbom-Plot) liegt zwischen 3 und 14.5 µg cm^–3. Spektroskopische Untersuchungen der Reaktion in Lösungen, entweder mit equimolaren Konzentrationen oder mit einem Überschuß an einer Komponente impH-Bereich 0.3–6.5, lassen Rückschlüsse auf mögliche Komplex-Übergänge in Lösung zu. Es wurde eine vollständige graphische, logarithmische Analyse der Absorptions-pH-Graphen durchgeführt, um die Komplexgleichgewichte in Lösung aufzuklären und zu charakterisieren. Unter den Optimalbedingungen kann Palladium als nichtgeladener Komplex Pd(AMHA)₂ in Gegenwart einer großen Anzahl an Fremd-Ionen bestimmt werden. Schwierigkeiten mit Zirkonium(IV) konnte durch Maskierung mit Fluorid-Ionen umgangen werden.

     

Indirect complexometric determination of small amounts of tellurium

Summary A complexometric method is proposed for the determination of small amounts of tellurium (50–350g). It is based on the reaction between Te(IV) and diethyldithiocarbamic acid (DDTC). The compound of the composition Te(DDTC)₄ obtained is extracted with CCl₄ at p_H 8.7–8.8. The yellow organic extract is shaken with copper(II)-ammonia solution, p_h 11. The organic phase, containing Cu(DDTC)₂ is then shaken with silver-ammonia solution. The Cu(II)-ions pass into the aqueous phase where they are titrated with 0.002M EDTA, using glycinethymol blue as indicator. Selenium(IV) does not interfere.

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Zusammenfassung Die Reaktion zwischen Te(IV) und Diäthyldithiocarbaminsäure (DDTC) wurde zur komplexometrischen Bestimmung kleiner Mengen Tellur (50 bis 350g benützt. Te(DDTC)₄ wird mit CCl₄ extrahiert (p_H 8,7 bis 8,8) und der gelb gefärbte organische Extrakt mit ammoniakalischer Cu(II)-Lösung bei p_h11 ausgeschüttelt. Dabei findet ein Austausch von Te(IV) gegen Cu(II) statt. Die Cu(II)-Ionen der organischen Phase werden mit ammoniakalischer Ag(I)-Lösung umgesetzt und gehen in die wäßrige Phase über, wo sie mit 0,002-m ÄDTA-Lösung gegen Glycinthymolblau titriert werden. Selen(IV) stört nicht.

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Résumé On propose une méthode complexométrique pour le dosage de petites quantités de tellure (50-350g). Elle est fondée sur la réaction entre Te-IV et l'acide diéthyldithiocarbamique (DDTC). On extrait par CCl₄ á p_H 8,7–8,8 le produit obtenu, de composition Te(DDTC)₄. On agite l'extrait organique jaune avec une solution ammoniacale de cuivre-II. Les ions cuivriques passent dans la phase aqueuse oú ils sont titrés par l'EDTA 0,002M, avec le bleu de glycinethymol comme indicateur. Le sélénium-IV n'interfére pas.

     

Phenoxthin as a reagent for the detection of small amounts of palladium

Zusammenfassung Es wurde gefunden, daß Phenoxthin (Di-o-phenylen-oxyd-sulfid) ein einfach anzuwendendes und sehr empfindliches Palladiumreagens für Tüpfelreaktionen ist. Das Reagens hat einen angenehmen Geruch und ist im Handel erhältlich. Es ist auch leicht nachFriedel-Crafts aus Diphenyloxyd und Schwefel herzustellen.     

The express simultaneous neutron activation determination of gold,palladium and platinum

The method of express neutron-activation (NA) determination of Au, Pd and Pt has been developed. The method is based on the quantitative isolation of¹⁹⁸Au+¹⁹⁹Au and¹⁰⁹Pd activities by extraction with organic sulfides. The radiation of¹⁰⁹Pd is measured on a thin NaI(Tl) crystal and that of¹⁹⁸Au and¹⁹⁹Au on a Ge(Li) detector. The calculations of interferences from gold have been performed for various neutron fluxes and various cadmium ratios. Some interferences introduced by other competitive nuclear reactions into the determination of Pt by its daughter isotope¹⁹⁹Au are discussed.     

Solid-phase extraction in the determination of gold, palladium, and platinum

A simple classification of various sorbents and solid-phase extraction procedures used for preconcentration of trace levels of Au, Pd, and Pt from different sample types is proposed in this review article. The large variety of available sorbents/procedures has been organized according to expected mechanisms of sorption process (complex formation; ion exchange; adsorption; ion-imprinted or molecularly imprinted polymers); according to the kind of monomeric units of the polymer matrix as well as on the basis of the kind of functional group responsible for main performance characteristics (selectivity, capacity) of the sorbent. Advantages of chemically modified sorbents, sulfur-containing sorbent extractants, and ion-imprinted polymers, together with rational pretreatment by means of microwave treatments, scaling down of enrichment, and quantification by means of flow and flow injection approaches are given. Preferred instrumental techniques for quantification of ppb levels of Au, Pd, and Pt in prepared concentrates/column eluates are multielement instrumental techniques: inductively coupled plasma optical emission spectrometry (ICP-OES), and inductively coupled plasma mass spectrometry (ICPMS). Excellent limits of detection at picogram levels of these analytes are provided by electrothermal atomic absorption spectrometry (ETAAS), generally in single-element mode and the neutron activation analysis (NAA), while X-ray fluorescence spectrometry and flame AAS are rarely applied because of lack of sensitivity at sub-ppm levels of Au, Pd, and Pt. Some problems of atomic spectrometric quantification techniques and their representative limits of detection are given. Recent applications to geological, industrial, pharmaceutical, biological, and other materials are tabulated. References have been selected mostly from the period 1995 to 2010.     

Analytical applications of ternary complexes-VI Spectrophotometric determination of trace amounts of palladium

Extremely sensitive and specific colour reactions in both aqueous and organic solutions are described for the spectrophotometric determination of palladium(II) ions. The methods are based upon ternary complex formation with 1,10-phenanthroline or pyridine, and Rose Bengal Extra. Themolar absorptivities are 5 × 10⁴ (aqueous) and 1.25 × 10⁵ (organic) in the presence of a 1000-fold molar excess of EDTA as mass masking agent. Under these conditions there is negligible interference with the pyridine-Rose Bengal Extra system from the 22 cations (including silver, gold and platinum) and seven anions investigated. Both colour reactions take place within 15 min and the complexes are stable for long periods.     

Catalytic determination of ultra trace amounts of palladium by linear sweep voltammetry

A sensitive method is proposed for the determination of palladium, based on its catalytic effect on the reduction of malachite green by hypophosphite. The reaction rate is monitored by measuring the current of product of reaction at −0.79 V vs. Ag/AgCl reference electrode. The linear dynamic range is 30.0–300.0 ng/mL with a limit of detection of 10.0 ng/mL. The interference effects of many ions were studied. The method was used for the determination of Pd(II) in synthetic samples of dental alloys with satisfactory results.     

Photometric determination of small amounts of magnesium in rocks

The method of Mann and Yoe has been adapted to the determination of small amounts of magnesium in a “rapid method” scheme of rock analysis. The effect of calcium is found to be different from that described by the original authors. Tricthanolamine is introduced as a masking agent for aluminum. Anomalous instability of the color system requires a revised photometric technique,     

The determination of small amounts of vanadium in the presence of large amounts of uranium

To eliminate the color interference of large amounts of uranium in the determination of vanadium by the Hamner method, the vanadium was separated prior to titration by the extraction of vanadium cupferrate with chloroform. The chloroform extract was evaporated with sulfuric acid and the excess cupferron removed by oxidation with nitric acid and perchloric acid. The vanadium was reduced with ferrous ammonium, sulfate solution, the excess ferrous ion oxidized with ammonium persulfate, and the vanadium (IV) titrated with 0.02 N potassium permanganate. As little as 1.02 mg of vanadium in the presence of 5 g of uranium oxide was determined accurately by this method.