Properties and analytical applications of the heteropolymolybdates of phosphorus, arsenic, silicon and germanium-II Modifications of the heteropoly acids

Phospho-, arseno-, silico- and germanomolybdic acids may all exist in an alpha- and a beta-modification. alpha-Silicomolybdic acid is formed if the degree of acidification is below [H(+)]/[Mo] = 1.5. At higher acid concentrations the beta-modification is formed, and spontaneously transformed into the alpha-form. Germanomolybdic acid behaves similarly, but the transformation is much faster. Arsenomolybdic acid is always formed as the alpha-modification and is transformed into the beta-modification only later and in a very slow reaction if the pH of the solution is below 1. Formation of the two modifications is also dependent on acid concentration in the case of phosphomolybdic acid, but both modifications are stable and no spontaneous transformation occurs. Compounds similar to the beta-modifications but showing different molar absorptivities are formed in acetone-containing solution.     

Properties and analytical applications of the heteropolymolybdates of phosphorus, arsenic, silicon and germanium-I Spectrophotometric examination of the heteropoly acids

Spectrophotometric studies have been made of the heteropoly acids of phosphorus, arsenic, silicon and germanium, formed at molybdate concentrations of 10(-1)-10(-3)M. It was found that the heteropoly anion is quantitatively produced at a Z-value of 1.60 in the case of a quinquevalent central atom and 1.50 for a quadrivalent central atom, if the amount of the latter is not higher than 50% of the stoichiometric (Z is the number of moles of protons taken up by one mole of molybdenum.) On addition of further acid the anion takes up protons, but its absorbance remains unchanged if measured at a wavelength at which the isopolymolybdates show no absorption. At Z-values higher than 2.2-2.3, i.e., in highly acidic media, a decomposition reaction starts; its products are octamolybdate and molybdenyl ions. The different molar absorptivities and other "irregularities" found in the various analytical procedures in the literature are due not to the heteropoly acids but to the isopolymolybdate formed together with the former.     

Properties and analytical applications of the heteropolymolybdates of phosphorus, arsenic, silicon and germanium-III Examination of two- and three-component systems without separation

By taking advantage of the possible variations in acid and molybdenum concentration, wavelength of measurement, alpha- and beta-modifications, and media, P, As, Si and Ge can be determined spectrophotometrically as the heteropolymolybdates without separation. Rapid procedures are proposed for the analysis of two- and three-component mixtures of these elements.     

Analytical applications of β-heteropoly acids : Part I. Determination of arsenic,germanium and silicon

The existence of two forms of several heteropolymolybdates, differing in structure and stability, was confirmed. The unstable β-forms were stabilised by addition of comparatively large amounts of polar organic solvents, especially acetone, presumably because the solvent displaces water from the surface of the heteropoly anion and so inhibits any reorganisation of the structure of the anion. The organic solvent also intensifies the colour. The methods are rapid, sensitive, precise and accurate. Various applications are described.     

Simultaneous determination of arsenic,phosphorus, and silicon

Summary A simple, rapid, accurate and reliable method for the simultaneous determination of arsenic, phosphorus and silicon in the presence of each other is reported. The method involves the selective solvent extraction of phosphomolybdic acid by isobutyl acetate, the differential formation of phospho and arsenomolybdic acid when perchloric acid is added before the addition of ammonium molybdate, and the selective destruction of phospho and arsenomolybdic acid complexes in the presence of silicomolybdic acid. Silicon, phosphorus and arsenic were determined as their heteropoly blues.

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Zusammenfassung Eine einfache, rasche und verläßliche Methode zur gleichzeitigen Bestimmung von Arsen, Phosphor und Silicium nebeneinander wurde beschrieben. Phosphormolybdänsäure wird selektiv mit Isobutylacetat extrahiert. Setzt man vor der Zugabe von Ammoniummolybdat Perchlorsäure zu, so erfolgt die Bildung von Phospho- bzw. Arsenomolybdänsäure in differenter Weise. Diese beiden Säuren sind in Gegenwart von Silicomolybdänsäure selektiv zerstörbar. Silicium, Phosphor und Arsen werden auf der Grundlage der blauen Farbreaktion ihrer Heteropolysäure bestimmt.

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Résumé On communique une méthode simple, rapide, précise et sûre pour le dosage simultané de l'arsenic, du phosphore et du silicium en présence les uns des autres. La méthode met en jeu l'extraction par solvant sélectif de l'acide phosphomolybdique par l'acétate d'isobutyle, la formation différentielle de l'acide phospho et arsénomolybdique quand l'addition de l'acide perchlorique précède celle du molybdate d'ammonium, et la destruction sélective des complexes acides phospho et arsénomolybdiques en présence d'acide silicomolybdique. On a dosé le silicium, le phosphore et l'arsenic sous forme d'hétéropolycomplexes bleus.

     

Application of total selective solvent extraction of germanium,phosphorus and silicon to the simultaneous determination of arsenic,germanium, phosphorus and silicon

A simple rapid, accurate, and reliable method of simultaneous determination of arsenic, germanium, phosphorus, and silicon is reported. The method involves first, the determination of germanium as its phenlfluorone complex and its selective extraction with isoamyl alcohol. Phosphorus is next determined as its heteropoly blue after selective extraction of phosphomolybdic acid by isobutyl acetate at pH 1.0-0.8 and its direct reduction in this solvent. Silicon is then determined after its extraction as silicomolybdic acid by isooctyl alcohol at pH < 0.4 and direct reduction in the solvent phase. Finally, arsenic is determined in the remaining aqueous phase after reduction to its heteropoly blue.     

Separation of molybdoheteropoly acids of phosphorus,arsenic, silicon and germanium as ion-associates by HPLC. Application to quantitative determination in water

Summary Very low concentrations of Si(IV), Ge(IV), As(V) and P(V) in natural waters are determined by HPLC. The method is based on solvent extraction of molybdoheteropoly compounds as ion associates with dichloromethane. Separation of the heteropoly compounds without decomposition is possible by using reversed phase systems, especially the CN-modified reversed phase. The method makes it possible to separate different modifications from each other and to quantify the rate of coextracted isopoly compound. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984     

Simultaneous determination of phosphorus. arsenic and germanium and the separation of silicon and arsenic by solvent extraction

A simple, rapid, accurate and reliable method for the simultaneous determination of phosphorus, arsenic and germanium as their heteropoly blue complexes is reported. The method involves selective extraction of phosphomolybdic acid at pH 1.0-0.8, and selective extraction of germanomolybdic acid by isooctyl alcohol at pH 0.4, followed by back-extraction of the germanomolybdic acid with water, and reduction of arsenomolybdic acid in the remaining aqueous phase. A rapid and reliable method is also reported for the simultaneous determination of arsenic and silicon by selective extraction of silicomolybdic acid with isooctyl alcohol at pH < 0.4 and the back-extraction of the silicomolybdic acid with water; arsenic is determined in the remaining aqueous phase. The procedure can be applied to the simultaneous determination of phosphorus, arsenic and silicon.     

Improvement of analytical sensitivities for the determination of antimony,arsenic, cadmium,indium, iodine,molybdenum, silicon and uranium in airborne particulate matter by epithermal neutron activation analysis

As part of an ongoing Great Lakes deposition study, we have determined a series of heavy metals in air filter samples collected near Lake Ontario. To decrease our detection limits for key elements used in our receptor modeling, we have employed instrumental epithermal neutron activation analysis (NAA) and Compton suppression techniques. Our detection limits were much better than those with thermal NAA, typically, 0.3 ng for Sb, 0.7 ng for As, 8 ng for Cd, 0.2 ng for In, 14 ng for I, 5 ng for Mo and 2 ng for U. Silicon, which is usually not reported in conventional NAA results for air filters, was routinely determined at the 60 g level. Accuracy was corroborated by analyzing the certified reference material concurrently.     

A study of the composition and properties of the ion-association complex of Rhodamine B with silicomolybdic acid, with a view to its analytical application

The composition of the ion-association complex of Rhodamine B with silicomolybdate has been examined by Job's method and spectrophotometric titration. The ratio of Rhodamine B to silicon in the complex is 4 : 1. The same ratio is obtained by analysis of the crystalline complex. The composition of the complex is identical in aqueous medium, an organic solvent (ethanol) and in the crystalline state (C(28)H(30)N(2)O(3))(4)SiMo(12)O(40)). The complex is stable in the organic solvent and has its absorption maximum at 555 nm and a molar absorptivity of 5 x 10(5) 1.mole(-1)cm(-1). The complex can be advantageously used for the determination of silicon.     

Determination of silicon,phosphorus and sulfur in alloy steel by neutron activation analysis

Silicon, phosphorus, and sulfur in alloy steel were determined by neutron activation analysis involving rapid radiochemical separation procedures. The standard deviations for silicon, phosphorus, and sulfur were 1.6%, 2.3%, and 2.4% respectively; the sensitivity limits were 3.2, 0.20, and 2.50 p.p.m., respectively. The three constituents could be determined in alloy steel within 2 h of the irradiation.     

Catalysis of the reaction of grignard reagents with silicon,tin, phosphorus,and arsenic halides and organohalides by copper salts with the formation of organic compounds of these elements

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 714–715, March, 1990.     

花菁-脱氧核糖核酸的共振光散射光谱及其分析应用

研究了一种苯并噻唑阳离子花菁与脱氧核糖核酸(DNA)作用的共振光散射光谱,在pH 6.0的六次甲基四胺-HCl缓冲介质中,痕量DNA的加入使花菁在590nm的共振光散射强度显著增强。在最佳实验条件下,增强的共振光散射强度与DNA浓度具有良好的线性关系,据此建立了一种测定DNA的共振光散射光谱法。方法的线性范围为:小牛胸腺DNA(CT DNA),0～20μg/mL,鱼精子DNA(FS DNA),0～15μg/mL;检出限分别为0.005μg/mL和0.008μg/mL。该方法已用于合成样品中DNA的测定。     

oxidmetric titration of triphenyl derivatives of phosphorus,arsenic, antimony and bismuth with N-bromosuccinimide

A simple direct titration for milligram and microgram amounts of triphenylphosphorus, -arsenic, -antimony, and -bismuth is described. The methanolic sample solution, with a little water, hydrochloric acid and bromide added, is titrated with N-bromosuccinimide to a methyl red end-point. All four compounds were titrated in the same way with recoveries of 99–100% and relative standard deviations of 1–5% were obtained.     

Determination of arsenic species: a critical review of methods and applications, 2000-2003

We review recent research in the field of arsenic speciation analysis with the emphasis on significant advances, novel applications and current uncertainties.     

Liquid extraction of molybdophosphoric and molybdoarsenic acids: application to the determination of phosphorus in the presence of arsenic

The radioisotopes phohphorus-32 and arsenic-74 have been used to study the extraction of molybdophosphoric and molybdoarsenic acids from aqueous solution with various organic solvents. A method is described for the gravivmetric determination of phosphorus in the presence of arsenic which makes use of solvent extraction with n-butyl acetate. The results obtained for the determination of phosphorus in various types of iron and steel are described.