Gravimetric determination of gold with di-2-thienylketoxime

Di-2-thienylketoxime may be used as a gravimetric reagent to determine gold. The error is of the order of ± 0.3%. There are few interfering ions and simple methods may be used to eliminate these.     

Sensitive determination of iron(III) by gold electrode modified with 2-mercaptosuccinic acid self-assembled monolayer

Preparation and application of gold 2-mercaptosuccinic acid self-assembled monolayer (Au-MSA SAM) electrode for determination of iron(III) in the presence of iron(II) is described by cyclic voltammetry, electrochemical impedance spectroscopy, and Osteryoung square wave voltammetry. The square wave voltammograms showed a sharp peak around positive potentials +0.250 V that was used for construction of the calibration curve. Parameters influencing the method were optimized. A linear range calibration curve from 1.0 × 10⁻¹⁰ to 6.0 × 10⁻⁹ M iron(III) with a detection limit of 3.0 × 10⁻¹¹ M and relative standard deviation (R.S.D.) of 6.5% for n = 8 at 1.0 × 10⁻⁹ M iron(III) was observed in the best conditions. Possible interferences from the coexisting ions were also investigated. The results demonstrated that sensor could be used for determination of iron(III) in the presence of various ions. The validity of the method and applicability of the sensor were successfully tested by determining of iron(III) in natural waters (tap and mineral waters) and in a pharmaceutical sample (Venofer^® ampoule) without interference from sample matrix. The experimental data are presented and discussed from which the new sensor is characterized.     

Gravimetric determination of copper(II) with p-aminobenzoic acid

A method has been developed for the gravimetric determination of 20-100 mg of copper(II) with p-aminobenzoic acid. Ag, Hg(II), Pb, Al, Fe(II), Bi, Sb(III) and Sn(II) interfere, but Zn, Co(II), Ni and Cd do not. The precipitate can be weighed after drying at 80-100 degrees , or can be ignited to copper(II) oxide at temperatures above 400 degrees , and weighed in this form.     

Gravimetric determination of gold with sodium salt of n-(n-bromo-c-tetradecyl betainyl)-c-tetradecylbetaine

The sodium salt of N-(N-bromo-C-tetradecyl betainyl)-C-tetradecyl betaine is presented as a gravimetrie reagent for the determination of gold. Two complexes have been isolated; one, precipitated from hydrochloric acid solution, containing 22.14% gold; the other, from hydrobromic acid solution, containing 18.01% gold. Both complexes may be dried to constant weight at 85° C, thus giving the advantage of a favorable weight factor. Determinations from hydrobromic acid solutions are more rapid and offer several other advantages. Optimum conditions have been established. The number of interfering ions is small and a method for thie separation of gold from these ions was developed. A procedure for the determination of gold in ore concentrates was applied to several samples with satisfactory results.     

Photochronometric determination of traces of gold(III)

Summary A method for the determination of traces of gold is based on the catalytic effect of Au(III) on the reduction of Ag(I) with Fe(II). The time elapsing from the addition of the Fe(II) solution to the appearance of a certain precipitation (determined photometrically) is measured and the Au content is read from a calibration curve. Interferences are caused by halogen and cyanide ions and by oxidizing agents. 45 ng of Au could be determined with a maximum error of 2.5 ng.

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Zusammenfassung Ein Verfahren zur Spurenbestimmung von Gold beruht auf der durch Goldionen katalysierten Reduktion von Silberionen mit Eisen(II). Hierbei wird die Zeit gemessen, die bis zum Auftreten einer gewissen Niederschlagsdichte vergeht, die photometrisch bestimmt wird. Der Goldgehalt ergibt sich aus einer Eichkurve. Halogen- und Cyanidionen sowie Oxydationsmittel verursachen Störungen. 45 ng Gold konnten mit einem Fehler von höchstens 2,5 ng wiedergefunden werden.

     

Gravimetric determination of uranium(VI) with pyridine-2,6-dicarboxylic acid

Uranium(VI) can be quantitatively precipitated from aqueous solution in the pH range 2.1-6.9 with pyridine-2,6-dicarboxylic acid in the presence of tetraphenylarsonium chloride. This provides a new rapid gravimetric method for uranyl ion as an organic chelate complex of high molecular weight. Sodium, aluminium, copper and nickel as well as nitrate, chloride, sulphate and acetate ions, do not interfere, but iron(III) and thorium(IV) do.     

Spectrophotometric determination of Fe(III) by using casein-functionalized gold nanoparticles

The preparation and application of casein-capped gold nanoparticles (AuNPs) as a specific probe for ferric ions Fe(III) is reported. The functionalized AuNPs exhibit narrow size distribution and form stable dispersions in water of different ionic strengths and basicity. The presence of diverse functional groups from the side chain of peptides warrants colloidal stability of AuNPs and also assists recognition of Fe(III) in versatile conditions. Fe(III) ion reportedly causes the aggregation of AuNPs and a red-shift in absorbance toward longer wavelength (660 nm). A spectrophotometric method is appropriate for selective detection of Fe(III) and the spectral shift is also accompanied by a color change from red to blue. The aggregation of AuNPs is not suppressed after the addition of NaOH or at moderate ionic strength. The resulting spectrophotometric method works for Fe(III) in the concentration range of 0.1 to 0.9 μM and has a detection limit of 450 nM. The AuNP probe can also detect Fe(III) ion content in real samples at the same detection limit, which is much lower than the maximum contaminant level allowed for Fe(III) in drinking water (5.37 μM) by the U.S. Environmental Protection Agency.

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Graphical abstract Casein peptide functionalized gold nanoparticles: synthesis, characterization, and their application to the visual detection of Fe(III).

     

Kinetic spectrophotometric method for gold(III) determination

The kinetic spectrophotometric method for Au(III) determination was developed and validated. It was based on the catalytic effect of gold on the oxidation of methylene blue B (3,7di-(dimethyl amino)-10-dehydro-phenotiazin chloride) by ammonium peroxo-disulfate in citric buffer solution. There was the linearity of the calibration curve in the concentration range from 0.09 to 2.90 μg ml⁻¹ Au(III). The relative standard deviation was 2.50% and correlation coefficient of 0.9999. The limit of detection was determined as signal to noise ratio (3:1) and it was 5.5 ng ml⁻¹. The limit of quantification, based on signal to noise ratio 10:1 was 19.25 ng ml⁻¹. The selectivity was tested on the basis of influence of known amounts of different ions in the reaction mixture, upon the reaction rate. Kinetic and thermodynamic parameters were reported for both catalytic and non-catalytic reactions. The method was verified by Au(III) determination in anti-rheumatic drug “Tauredon” and in human urine samples, using ICP-AES as the comparative method. As the method is accurate, reliable, quick and simple it could be useful for clinical and toxicological practice.     

Gravimetric determination of palladium with 2-(o-Hydroxyphenyl) benzoxazole

Summary A method has been developed for the direct gravimetric determination of palladium. The method saves time and is reproducible and accurate. Of the several cations and anions studied, only a few of the cations interfered seriously with the determination of palladium.     

Synergetic extraction and spectrophotometric determination of gold(III)

Summary A method is described for the synergetic extraction and subsequent spectrophotometric determination of gold(III). The gold--furil dioxime-pyridine complex extracted into chloroform has a characteristic yellow colour with an absorption maximum at 330 nm. Beer's law is obeyed in the concentration range [Au(III)]45g/ 10 ml organic phase. A scheme to separate gold from interfering elements by extraction with 4-methyl-2-pentanol in benzene has been proposed.

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Zusammenfassung Ein Verfahren zur synergetischen Extraktion und nachfolgenden spektrophotometrischen Bestimmung von Gold(III) wurde beschrieben. Die Komplexverbindung des Goldes mit-Furildioxim und Pyridin ist in chloroformischer Lösung gelb gefärbt. Ihr Absorptionsmaximum liegt bei 330 nm. Bis 45g Au(III)/10 ml organischer Phase wird das Beersche Gesetz befolgt. Die Trennung des Goldes von störenden Elementen durch Extraktion mit 4-Methyl-2-pentanol in Benzol wurde vorgeschlagen.

     

Gravimetric determination of cadmium with N-phenylbenzohydroxamic acid

A quantitative gravimetric determination of cadmium in presence of Ag(+), Be(2+), Pb(2+), Mn(2+), Ni(2+), Cu(2+), Zn(2+), Hg(2+), Pd(2+), Ga(3+), Al(3+), Bi(3+), Sb(3+), La(3+), Ti(4+), Zr(4+), V(5+), Mo(6+) and U(6+) was made by selective precipitation with N-phenylbenzohydroxamic acid from a solution containing 6-15 mg of cadmium acetate at pH 5.8-6.5. The precipitate was weighed directly after drying at 110-120 degrees . The cadmium complex is curdy white, granular and melts at 225 degrees. The analytical results indicate the complex to be (C(13)H(10)NO(2))(2)Cd.     

Spectrophotometric determination of microamounts of gold(III) with propericiazine

Propericiazine is proposed as a new reagent for the spectrophotometric determination of gold(III). The reagent forms an orange-red-colored species with gold(III) instantaneously in 4–8 M phosphoric acid. The orange-red species exhibits maximum absorbance at 511 nm. Beer's law is valid over the concentration range 0.1–7.0 μg/ml. The molar absorptivity is found to be 3.85 × 10⁴ liter mol⁻¹ cm⁻¹. The effects of acidity, time, order of addition of reagents, temperature, reagent concentration, and diverse ions are investigated.