Electrocatalysis by ad-atoms: Part IX. A fast parallel path for formaldehyde oxidation on a platinum electrode by oxygen adsorbing ad-atoms

The effect of various ad-atoms on formaldehyde oxidation was examined on a Pt electrode. Ad-atom species are found to be classified into two groups according to their way of affecting the electrode reaction: one consists of Cu, Ag, Tl, Hg, Pb, As, Bi, Te and Se, the other Ge, Sn and Sb. The enhancement effect of the former depends on the number of Pt sites occupied by an ad-atom of each species (S_M), which suggests to us that geometrical control of Pt site arrangement plays an important role in the enhancement. The latter group of ad-atoms adsorb oxygen atoms, and these oxygen atoms are considered to play an important role in this enhancement. The enhancement ratio by the latter group of ad-atoms is much greater than that by the former group. The enhancement by the latter group of ad-atoms is via a new rapid parallel path, which has not been found on a Pt electrode for formaldehyde oxidation.     

Solvent extraction of metal xanthates

The solvent extraction of metal xanthates is reviewed with emphasis on the characteristics and analytical uses of ethyl xanthate complexes. Elements reviewed include As, Sb, Bi, Cd, Co, Cu. Cr, Ga, Au, In, Fe, Pb, Mn, Hg, Mo, Ni, Pd, Pt, Re, Ag, Se, Te, Tc, Tl, Sn, U, V and Zn.     

Estimation of Uncertainty Budgets in Analysis of Nickel by ICP-MS and High-Resolution Mass Spectrometry with a Glow Discharge

Moscow University Chemistry Bulletin - This paper estimates uncertainty budgets in determining the content of impurities of 15 elements (P, Mn, Fe, Cu, Zn, As, Se, Ag, Cd, Sn, Sb, Te, Tl, Pb, Bi)...     

Polarographic determination of cadmium, lead, nickel, thallium and uranium(VI) in isoquinoline formate

Summary The polarographic behaviour of Cd, Pb, Ni, Tl and U(VI) has been described in 0.1 M isoquinoline formate as base electrolyte. In all cases well defined reversible waves were obtained and determinations are possible in the presence of Mo, Co, Zn, Mn, Te, In, Se, Fe, Cr, V, Th, Zr, As, Sb, Ag, Hg and Cu.

---

Polarographische Bestimmung von Cadmium, Blei, Nickel, Thallium und Uran(VI) in Isochinolinformiat

Zusammenfassung Das polarographische Verhalten von Cd, Pb, Ni, Th. und U(VI) in 0,1 M Isochinolinformiatlösung wird beschrieben, Bestimmungsmöglichkeiten werden aufgezeigt. In allen Fällen werden gut definierte reversible Stufen erhalten. Folgende Elemente stören nicht: Mo, Co, Zn, Mn, Te, In, Se, Fe, Cr, V, Th, Zr, As, Sb, Ag, Hg, Cu.

     

Comparison of tungsten coil electrothermal vaporization and thermospray sample introduction methods for flame furnace atomic absorption spectrometry

Flame furnace atomic absorption spectrometry (FF-AAS) is a newly developed flame atomic absorption spectrometric technique based on arranging a flame furnace onto the top of the flame burner head. In this fundamental investigation, 25 elements were carefully tested by using either thermospray FF-AAS or tungsten coil electrothermal vaporization FF-AAS, of which 15 volatile and semi-volatile elements (Cd, Tl, Ag, Pb, Zn, Hg, Cu, Sb, Bi, Te, In, As, Se, Sn and Au) exhibited better limits of detection compared to those by conventional FAAS; however, non-volatile or refractory elements (Fe, Co, Ni, Cr, Mn, Pd, Pt, Al, Be and V) showed inferior sensitivities by the proposed methods.     

Metal chelate exchange in the organic phase-II Extraction and exchange constants of dithizonates and diethyldithiocarbamates

Dithizonates and diethyldithiocarbamates of Ag, Tl(I), Cu(II), Zn, Cd, Hg(II), Pb, Fe(II), Co(II), Ni, Pd(II), In(III), As(III), Sb(III), Bi, Se(IV) and Te(IV) have been prepared and their reactions in carbon tetrachloride have been studied spectrophotometrically. From the exchange constants determined, the extraction constants of metal diethyldithiocarbamates have been calculated. Where formation of mixed chelates has been observed, corresponding exchange constants have been determined. Finally, the influence of organic solvents (CCl(4), CHCl(3), C(6)H(6) and C(6)H(5)Cl) on the exchange reaction of zinc diethyldithiocarbamate with dithizone has been investigated.     

Electrocatalysis by ad-atoms: Part XVII. Electronegativity effect on oxygen donation by oxygen-adsorbing ad-atoms and steric hindrance by alkyl groups in Shole control in aldehyde oxidation

The oxidation of propionaldehyde was examined on electrodes modified by Ru, Ag, Hg, Ge, Sn, As, Sb, Bi, S, Se and Te ad-atoms. The feature of the enhancement of propionaldehyde oxidation by ad-atoms was found to be quite similar to that of formaldehyde and acetaldehyde oxidation. The oxidation was found to be enhanced strikingly by oxygen donation by oxygen-adsorbing ad-atoms as well as by the inhibition of poison formation by S_hole control by non-oxygen-adsorbing ad-atoms, but to a lesser extent. In the enhancement by S_hole control, steric hindrance by alkyl groups is observed. In the enhancement by oxygen-adsorbing ad-atoms, the difficulty in oxygen donation from ad-atoms to aldehyde molecules depends on the size of the alkyl group: the smaller the electronegativity of the oxygen-adsorbing ad-atoms, the more difficult is this donation. The donation is discouraged by the orientation of aldehyde molecules caused by the induced negative charge of adsorbed oxygen atoms.     

Methyl isobutyl ketone extraction of iodide complexes from sulphuric acid-potassium iodide media and back-extraction into an aqueous phase

The methyl isobutyl ketone extraction of 15 elements (Cu, Ag, Zn, Cd, In, Tl, Ge, Sn, As, Sb, Bi, Se, Te, Mo and Pd) as iodide complexes from 0.1-5 M sulphuric acid/0.01-0.5M potassium iodide media has been studied. At the optimum potassium iodide concentrations, and a 1:2 v v ratio of organic to aqueous phase, Cu(II), Ag, Cd, In(III), Tl(III), Sb(III), Bi, Te(IV) and palladium(II) are completely extracted in a single step from 1-5M sulphuric acid. All these elements except palladium are also quantitatively extracted from 0.05-0.5M iodide/2M sulphuric acid. Zn, Sn(IV) and As(III) are completely extracted at high acid and iodide concentrations, and at the highest concentrations of acid and iodide investigated, Ge is partly extracted and Mo(VI) is slightly extracted. The extraction of Se(IV) is incomplete because of its reduction to the elemental state by iodide. The back-extraction of the elements has also been investigated and the forms in which they are extracted and potential analytical separations and interferences are discussed.     

Determination of extraction constants of metal diethyldithiocarbamates

The extraction of metal diethyldithiocarbamates (Mn, Fe, Co, Ni, Pd, Cu, Ag, Zn, Cd, Hg, In, Tl, Pb and Bi) into carbon tetrachloride was investigated in order to establish the extraction constants and two-phase stability constants. The order of extractability of these chelates was determined.     

Electrocatalysis by ad-atoms: Part VIII. Ag,Pb, Te and Tl ad-atoms for ethylene reduction

As already reported, ethylene reduction at a Pt electrode can be enhanced by ad-atoms of Cu and Hg. Another series of ad-atom species is reported, that is, Ag, Pb, Tl and Te, in which the enhancement order depends on the number of Pt sites occupied by an ad-atom. S_M. This effect originates from the difference between S_M and the number of Pt sites occupied by an ethylene molecule, which causes an increase in the number of Pt sites available for hydrogen adsorption. This increase results in the enhancement, in the order Ag>PbTl; Te which has the same S as ethylene has no enhancement effect.For the complete understanding of the function of the mixed surface in the electrocatalysis, a new concept, “catalytic domains”, parts of the mixed surface effective for the electrocatalysis, is introduced, on the assumption that the reaction rate is much higher than the rate of surface migration of the adsorbed species. Then the number of Pt sites which belong to the catalytic domain is calculated. Another concept, “reaction unit mesh”, is also introduced.     

Chloroform extraction of ethyl xanthate complexes from sulphuric acid media

The chloroform extraction of 30 elements (Fe, Co, Ni, Zn, Cd, Ge, Sn, V, As, Sb, Bi, Cu, Ag, Au, Mn, Re, Ga, In, Tl, Se, Te, Cr, Mo, U, Pt, Pd, Rh, Ir, Ru and Ce) from 0.1-8M sulphuric acid in the presence of potassium ethyl xanthate has been studied. Pd(II), Bi, As(III), Sb(III), Se(IV) and Te(IV) are completely extracted and Au(III) is largely extracted over the range of acid concentration investigated. Fe(II), Tl(I), Rh(III) and Cr(VI) are only slightly extracted and Se(VI), Te(VI), Ru(III), Cr(III), Mn(II), Zn, Ce(IV), Ir(IV) and Ge(IV) are not extracted at all. Depending on the acid concentration, the remaining elements are all partly extracted. Results are compared with those obtained in an earlier study of the extraction of xanthate complexes from hydrochloric acid media. The processes involved in the formation of some xanthate complexes and potential analytical separations are discussed.     

Distribution of some major and trace elements in Danube Delta lacustrine sediments and soil

Sediment cores collected from lakes Mesteru and Furtuna (eastern part), Sontea channel and soil samples collected from Caraorman bar, all located in the Danube Delta, were analyzed for 42 elements (Ag, Al, As, Be, Na, Mg, P, S, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Br, Rb, Sr, Y, Mo, Ag, Cd, In, Sn, Sb, Cs, Ce, Hf, Hg, Tl. Pb, Bi, Th. U) by instrumental neutron activation analysis (INAA), thick target proton induced X-ray emission (TT-PIXE) and inductively coupled plasma-mass spectrometry (ICP-MS). The INAA and TTPIXE yielded total concentrations whereas the ICP-MS data reflected the fractions soluble in 14M HNO₃. The ICP-MS data exhibited surface enrichment relative to the lower part of the sediment core of Cu, Zn, As, Ag, Cd, In, Sn, Sb, Hg, Tl, Pb, and Bi, most prominently by Cd and Hg. Their vertical distribution in the investigated cores generally reflected the pollution history of recent sediments in Danube delta, showing a steady increase until the end of the 1980s followed by a slow decrease after 1990. The vertical profiles of most remaining elements were characterized by a relatively uniform distribution along the cores. In some cases, the concentrations of As, Cd, Cu, Cr, Mn, Ni and Pb exceeded minimum thresholds of safety, as defined by the Romanian regulations. The elemental composition of the sediment below 20 cm depth (total concentrations) was similar to that of the upper continental crust (UCC) for most elements. Values distinctly higher than UCC were observed for As, Sb (factor ~5) and Cr, Ni, Cu (factor 2 to 3). The nitric acid soluble element concentrations in the soil samples in some cases showed increased values at the surface as compared to 30 cm depth, either due to air pollution or to the action of plants. In no case a large contribution to the topsoil from atmospheric deposition was evident, indicating that the surface contamination of the sediments was mainly by riverine transport. This revised version was published online in July 2006 with corrections to the Cover Date.     

Metal chelate exchange in the organic phase-III Extraction and exchange constants of dithizonates and oxinates

Reactions between dithizonates and oxinates of Ag, Tl(I), Cu(II), Zn, Cd, Hg(II), Pb, Co(II), Ni, Pd, In, Ga and Bi in chloroform have been studied spectrophotometrically. From the exchange constants determined, the extraction constants of metal dithizonates or metal oxinates have been calculated. By this method extraction constants of many metal chelates can be calculated which are difficult to determine by studies of distribution between aqueous and chloroform phases.     

The certification of the contents of Cd, Co, Cu, Fe, Hg, Ni, Pb, Zn, Sb, Se, Tl and Cr in a city waste incineration ash

Summary The analysis of ashes being of increasing importance, a reference material was prepared from fly ash of a city waste incinerator. The procedures of preparation, homogeneity and stability testing are described as well as the way of certification of elements of major importance: Cd, Co, Cr, Cu, Fe, Hg, Ni, Pb, Zn, Sb, Se and Tl.

---

Zertifizierung der Gehalte an Cd, Co, Cu, Fe, Hg, Ni, Pb, Zn, Sb, Se, Tl und Cr in einer Stadtmüll-Verbrennungsasche

Zusammenfassung Da die Analyse von Aschen zunehmend an Bedeutung gewinnt, wurde von der Flugasche einer Stadtmüll-Verbrennungsanlage ein Referenzmaterial hergestellt. Die Methoden der Herstellung sowie der Homogenitätsund Stabilitätsprüfung werden beschrieben und die Art der Zertifizierung der Elemente von hauptsächlicher Bedeutung aufgezeigt (Cd, Co, Cr, Cu, Fe, Hg, Ni, Pb, Zn, Sb, Se, Tl).

     

Strategy for water analysis using ICP-MS

The developed strategy permits determination in three steps of sixty-seven elements using inductively coupled plasma mass spectrometry (ICP-MS). Sodium, Mg, Si, S, Cl, K, and Ca are determined in a first step; B, Al, P, Cr, Fe, Mn, Ni, Cu, Zn, As, Se, Ag, Cd, Sb, Ba, Hg, and Pb are determined in a second step; and Li, Be, Ti, V, Co, Ga, Ge, Br, Rb, Sr, Y, Zr, Nb, Mo, Sn, Te, I, Cs, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, W, Pt, Au, Tl, Bi, Th, and U are analyzed in a third step. The figures of merit obtained are adequate to carry out water quality monitoring and other hydrochemical studies, such those based in the application of hydrochemical fingerprinting to water management.     

Chloroform extraction of metal ethyl xanthates from hydrochloric acid media

The chloroform extraction of 32 elements (Fe, Co, Ni, Zn, Cd, Ge, Sn, Pb, V, As, Sb, Bi, Cu, Ag, Au, Mn, Re, Ga, In, Tl, Ce, Se, Te, Cr, Mo, U, Pt, Pd, Rh, Ir, Ru and Os) from O.1-10M hydrochloric acid media in the presence of potassium ethyl xanthate has been studied. The oxidation states in which some elements react, and potential analytical separations, are discussed. Pd(II), As(III) and Se(IV) are completely extracted as ethyl xanthate complexes, Te(IV) is almost completely extracted, and Au(III) is largely extracted over the range of acid concentration investigated. Mn(II), Zn, Rh(III), Ir(IV), Ru(III), Os(IV), Cr(III), Cr(VI), Ce(III) and Ce(IV) are not extracted. Ge is partly extracted from 6-10M media as the chloro-complex. Depending on the acid concentration, the remaining elements are all partially extracted as xanthate complexes.     

Analytical applications of potassium thiocarbonate (PTC) reagent in the ring oven technique

Summary A systematic scheme of qualitative analysis of 20 metal-ions present in one drop of solution has been worked out using potassium thiocarbonate (PTC) reagent on theWeisz ring oven. Iron and selenium present as impurities in the filter paper have been removed by PTC in one operation as both form soluble complexes with PTC. Estimation of the strength of PTC solutions and of micro amounts of Ag, Tl, Pb, Cd, Bi, Cu, As, Sb and Se has been carrried out. The limit of identification of these metals on ring oven using PTC reagent have been studied. Estimation of binary mixtures comprising Cu-Cd, Cu-Ni, Ni-Zn, Co-Zn and Fe-Ti present in micro amounts has been accomplished using PTC reagent and based on ring-colorimetry.

---

Zusammenfassung Ein Analysenschema für den Nachweis von 20 Metallionen unter Verwendung eines Tropfens Probe und von Kaliumthiocarbonat (KTC) als Reagens auf dem Ringofen nachWeisz wurde ausgearbeitet. Im Filterpapier anwesendes Eisen und Selen werden mit dem Reagens ausgewaschen, da sich lösliche Komplexe bilden. Die Schätzung der KTC-Konzentration sowie kleiner Mengen Ag, Tl, Pb, Cd, Bi, Cu, As, Sb und Se läßt sich durchführen. Die Erfassungsgrenzen dieser Elemente mit KTC auf dem Ringofen wurden ermittelt. Binäre Gemische kleiner Mengen von Cu und Cd, Cu und Ni, Ni und Zn, Co und Zn, sowie Fe und Ti wurden mit KTC ring-kolorimetrisch analysiert.

     

Preconcentration of trace elements by partial dissolution of the matrix—multielement preconcentration from manganese

Trace elements such as Ag, Au, Bi, Cd, Co, Cu, Fe, Ga, In, Ni, Pb, Pd and Tl, can be preconcentrated with recoveries of better than 95% from high-purity manganese if the sample is coated with a thin layer of mercury before its dissolution in HCl to a small residue. For determination of the trace elements, the residue is completely dissolved in aqua regia. After separation of the mercury by reductive precipitation, Bi, Cd, Co, Cu, Fe, Ga, In, Ni, Pb, and Tl are determined by flame a.a.s. ('injection method'). Ag, Au and Pd are determined in the mercury-containing solution. The relative standard deviation was usually about 5%; Cu, Fe and Pb were proved to be inhomogeneously distributed in the sample (electrolytically produced manganese), and so the standard deviations were considerably greater. The detection limits for the different elements were between 0.6 and 0.004 ppm, depending on the sensitivity of their a.a.s. determination. The theoretical basis of this preconcentration method and its applicability to multielement analysis of different high-purity metals are discussed.