Optimization of parameters for semiempirical methods. III Extension of PM3 to Be,Mg, Zn,Ga, Ge,As, Se,Cd, In,Sn, Sb,Te, Hg,Tl, Pb,and Bi

Using a recently developed procedure for optimizing parameters for semiempirical methods,¹ PM3 has been extended to a total of 28 elements. Average ΔH_f errors for the newly parameterized elements are Be: 8.6, Mg: 8.4, Zn: 5.8, Ga: 14.9, Ge: 11.4, As: 8.5, Se: 11.1, Cd: 2.6, In: 11.3, Sn: 9.0, Sb: 13.7, Te: 11.3, Hg: 6.8, Tl: 6.5, Pb: 7.4, and Bi: 10.9 kcal/mol. For some elements the paucity of data has resulted in a method, which, while highly accurate, is likely to be only poorly predictive.     

Optimization of a single-drop microextraction method for multielemental determination by electrothermal vaporization inductively coupled plasma mass spectrometry following in situ vapor generation

A headspace single-drop microextraction (HS-SDME) method has been developed in combination with electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) for the simultaneous determination of As, Sb, Bi, Pb, Sn and Hg in aqueous solutions. Vapor generation is carried out in a 40 mL volume closed-vial containing a solution with the target analytes in hydrochloric acid and potassium ferricyanide medium. Hydrides (As, Sb, Bi, Pb, Sn) and Hg vapor are trapped onto an aqueous single drop (3 µL volume) containing Pd(II), followed by the subsequent injection in the ETV. Experimental variables such as medium composition, sodium tetrahydroborate (III) volume and concentration, stirring rate, extraction time, sample volume, ascorbic acid concentration and palladium amount in the drop were fully optimized. The limits of detection (LOD) (3σ criterion) of the proposed method for As, Sb, Bi, Pb, Sn and Hg were 0.2, 0.04, 0.01, 0.07, 0.09 and 0.8 µg/L, respectively. Enrichment factors of 9, 85, 138, 130, 37 and 72 for As, Sb, Bi, Pb, Sn and Hg, respectively, were achieved in 210 s. The relative standard deviations (N = 5) ranged from 4 to 8%. The proposed HS-SDME-ETV-ICP-MS method has been applied for the determination of As, Sb, Bi, Pb, Sn and Hg in NWRI TM-28.3 certified reference material.     

电感耦合等离子体质谱法测定高纯金中铝、砷、铋、铬、铁、铅、锑、硒、碲、铱痕量元素

建立了微波消解-内标法-标准加入-ICP-MS法测定高纯黄金中铝、砷、铋、铬、铁、铅、锑、硒、碲、铱等痕量元素的分析方法。从试样溶解方式、内标元素及同位素的选择、仪器检测模式的优化及降低基体抑制效应等方面进行优化。实验加标回收率为99.5%~110%,相对标准偏差(RSD)为0.050%~6.5%。实验的准确度和精密度良好,操作便捷。     

Atomic line profile measurements on hollow-cathode and electrodeless discharge lamps using a high-resolution echelle monochromator

Commercial r.f.-excited electrodeless discharge lamps (EDLs) and hollow-cathode lamps (HCLs) of the elements As, Bi, Cd, Sb, Se, Sn, Te and Zn were studied using a 2.54-m scanning echelle monochromator. The variation of the widths of the resonance lines from these lamps was investigated for a range of power and current levels. In general, the tendency to self-absorption and self-reversal is greater for the more volatile elements, although the strong self-reversal of the Pb 217.0 nm line from a HCl is an exception. EDLs for the less volatile elements, which are incorporated as iodides, show relatively little variation in line width except at the highest powers.The extent of the overlap between the Bi and I atomic lines at 206.2 nm is demonstrated and, for As, a hyperfine structure splitting constant (A-value) of 0.016 cm⁻¹ was determined for the 5s⁴P energy level.     

Multi-elemental analysis of marine sediment reference material MESS-3: one-step microwave digestion and determination by high resolution inductively coupled plasma-mass spectrometry (HR-ICP-MS)

Single-step microwave digestion methods using four different acidic dissolving reagents were investigated with the main objective to obtain a simple, rapid method for multi-elemental analysis of marine sediment samples by high resolution inductively coupled plasma-mass spectrometry (HRICP-MS), especially for environmental studies. Closed-vessels microwave digestion procedures were carried out using the reagents as follows: HNO₃, mixture of HNO₃-HCl (φ _r = 9: 1), aqua regia, and mixture of HNO₃-HCl-HF (φ _r = 8: 1: 1). The elements analyzed were: Al, As, Ba, Be, Bi, Cd, Co, Cr, Cu, Fe, K, Li, Mn, Mo, Na, Ni, Pb, Sb, Sn, Sr, Ti, Tl, V, and Zn. Good recoveries were established for many of the metals analyzed even when only nitric acid was employed. However, for a good recovery of Sb and Tl, aqua regia should be employed.     

UV photochemical vapor generation-atomic fluorescence spectrometric determination of conventional hydride generation elements

A systematic investigation of UV photochemical vapor generation (photo-CVG) and its potential application for seven typical hydride-forming elements (As, Sb, Bi, Te, Sn, Pb and Cd) when combined with atomic fluorescence spectrometry (AFS) detection is presented. These analyte ions were converted to volatile species following UV irradiation of their aqueous solution to which low molecular weight organic acids (such as formic, acetic or propionic acid) had been added, and introduced to an atomic fluorescence spectrometer for subsequent analytical measurements. The experimental conditions for photo-CVG and the interferences arising from concomitant elements were carefully investigated. Limits of detection as low as 0.08, 0.1, 0.2 and 0.5 ng mL^− 1 were obtained for Te, Bi, Sb and As, respectively, comparable to those by hydride generation-AFS. The RSDs obtained with the proposed method for these elements were better than 5% at 50 ng mL^− 1. It is noteworthy that the presence of TiO₂ nanoparticles combined with UV irradiation remarkably enhances the CVG efficiencies of Se(VI) and Te(VI), which cannot form hydrides with KBH₄/NaBH₄. Moreover, photo-CVG has a greater tolerance toward interferences arising from transition elements than hydride generation, and this facilitates its application to the analysis of complicated sample matrices.     

Phenyl Derivatives of Antimony(III,V) and Bismuth(III,V) in the Presence of Palladium Salts,as C-Phenylating Agents for Methyl Acrylate

The C-phenylation of methyl acrylate to methyl cynnamate with Ph₃Sb, Ph₃SbX₂ (X = Cl, OAc), Ph₃Bi, and Ph₃BiX₂ (X = OAc, O₂CEt) in the presence of PdCl₂, Pd(OAc)₂, Li₂PdCl₄, NaPd(OAc)Cl₂, and Na₂Pd(OAc)₂Cl₂ was studied to show that the reactions with Ph₃Sb and Ph₃Sb(OAc)₂ are more selective and give higher yields of the target product than those with Ph3Bi and Ph₃Bi(OAc)₂, while Ph₃M(OAc)₂ are preferred over Ph₃M. Copper(II) alkanecarboxylate additives have no effect on the yield of methyl cynnamate in the reactions with Ph₃Sb.     

Carbonat-isostere Anionen [SnX3]5− in den Verbindungen Rb6[SnX3]O0,5 und Cs6[SnX3]O0,5 mit X = As,Sb und Bi

Carbonate Isostructural Anions [SnX₃]^5? in the Compounds Rb₆[SnX₃]O_0.5 and Cs₆[SnX₃]O_0.5 with X = As, Sb, and Bi The metallic shining compounds Rb₆[SnX₃]O_0.5 and Cs₆[SnX₃]O_0.5 with X = As, Sb, and Bi were prepared from the melt starting from adequate mixtures of the elements and SnO₂. They crystallize in the hexagonal system (space group P6₃/mmc, No. 194, Z = 2) with the lattice constants mentioned in ?Inhaltsübersicht”?. In the structures of the isotypic compounds tin and the main group(V) elements build up trigonal planar anions [SnX₃]^5? with X = As, Sb, and Bi isostructural to the carbonate anion, oxygen forms isolated O^2? ions. The bond lengths Sn? X are significantly shortened with respect to the sums of Pauling covalent radii. The atoms of the units [SnX₃]^5? are coordinated by alkali metal cations forming trigonal prisms and the O^2? anions occupy octahedral holes.     

1,3,5‐Triphenyladamantane and 1,3,5,7‐tetraphenyladamantane

In 1,3,5‐triphenyladamantane, C₂₈H₂₈, (I), and 1,3,5,7‐tetraphenyladamantane, C₃₄H₃₂, (II), the molecules possess symmetries 3 and , and are situated across threefold and fourfold improper axes, respectively. The molecules aggregate by means of extensive C—H...π interactions. In (I), the pyramidal shape of the molecules dictates the formation of dimers through a `sixfold phenyl embrace' pattern. The dimers are linked to six close neighbors and constitute a primitive cubic net [H...π = 2.95 (2) and 3.02 (2) Å]. Compound (II) is isomorphous with tetraphenyl derivatives EPh₄ of group 14 (E = C–Pb) and ionic salts [EPh₄][BPh₄] (E = P, As and Sb). The multiple C—H...π interactions arrange the molecules into chains, with a concerted action of CH (phenyl) and CH₂ (adamantane) groups as donors [H...π = 3.15 (2) and 3.44 (2) Å, respectively]. The additional interactions with the methylene groups (four per molecule) are presumably important for explaining the high melting point and insolubility of (II) compared with the EPh₄ analogs.     

Coordination Complexes of Ph3Sb2+ and Ph3Bi2+: Beyond Pnictonium Cations

The syntheses of salts containing ligand‐stabilized Ph₃Sb²⁺ and Ph₃Bi²⁺ dications have been realized by in situ formation of Ph₃Pn(OTf)₂ (Pn=Sb or Bi) and subsequent reaction with OPPh₃, dmap and bipy. The solid‐state structures demonstrate diversity imposed by the steric demands and nature of the ligands. The synthetic method has the potential for broad application enabling widespread development of the coordination chemistry for Pn^V acceptors.     

Toxic mineral elements in Mytilus galloprovincialis from Sicilian coasts (Southern Italy)

Abstract

We assessed the relationship between V, Cr, Mn, Hg, As, Cd, Sn, Sb and Pb concentrations in Mytilus galloprovincialis samples from the coasts of Sicily and the expression of metallothioneins. Toxic mineral elements assessment was carried out by A.A. Spectrometry and ICP-MS. The metallothioneins expression was performed by q-PCR method. Low metals’ levels were found in the mussel samples examined, in comparison with what was reported in literature. The highest mean values of toxic mineral elements were found in Gela (Cr 0.178?±?0.03?mg/Kg, Mn 4.325?±?0.012?mg/Kg, As 3.706?±?0.009?mg/Kg, Sn 0.148?±?0.014?mg/Kg, Sb 0.009?±?0.004?mg/Kg e Pb 0.364?±?0.01?mg/Kg). Significant levels of Hg were found in samples from Catania (0.014?±?0.005?mg/Kg). Only vanadium and lead concentrations showed significant differences between sampling areas (p?<?0.05). Molecular analysis verified a basal expression of Mt1 and the absence of over-expression of Mt2, confirming the low mineral’s concentrations found in the samples examined.     

Sediment Assessment of the Pchelina Reservoir,Bulgaria

The temporal dynamics of anthropogenic impacts on the Pchelina Reservoir is assessed based on chemical element analysis of three sediment cores at a depth of about 100–130 cm below the surface water. The ¹³⁷Cs activity is measured to identify the layers corresponding to the 1986 Chernobyl accident. The obtained dating of sediment cores gives an average sedimentation rate of 0.44 cm/year in the Pchelina Reservoir. The elements’ depth profiles (Ti, Mn, Fe, Zn, Cr, Ni, Cu, Mo, Sn, Sb, Pb, Co, Cd, Ce, Tl, Bi, Gd, La, Th and U_nat) outline the Struma River as the main anthropogenic source for Pchelina Reservoir sediments. The principal component analysis reveals two groups of chemical elements connected with the anthropogenic impacts. The first group of chemical elements (Mn, Fe, Cr, Ni, Cu, Mo, Sn, Sb and Co) has increasing time trends in the Struma sediment core and no trend or decreasing ones at the Pchelina sampling core. The behavior of these elements is determined by the change of the profile of the industry in the Pernik town during the 1990s. The second group of elements (Zn, Pb, Cd, Bi and U_nat) has increasing time trends in Struma and Pchelina sediment cores. The increased concentrations of these elements during the whole investigated period have led to moderate enrichments for Pb and U_nat, and significant enrichments for Zn and Cd at the Pchelina sampling site. The moderately contaminated, according to the geoaccumulation indexes, Pchelina Reservoir surface sediment samples have low ecotoxicity.     

Establishing the Coordination Chemistry of Antimony(V) Cations: Systematic Assessment of Ph4Sb(OTf) and Ph3Sb(OTf)2 as Lewis Acceptors

The coordination chemistry of the stiboranes Ph₄Sb(OTf) ( 1 a , OTf = OSO₂CF₃) and Ph₃Sb(OTf)₂ ( 3 ) with Lewis bases has been investigated. The significant steric encumbrance of the Sb center in 1 a precludes interaction with most ligands, but the relatively low steric demands of 4‐methylpyridine‐N‐oxide (OPyrMe) and OPMe₃ enabled the characterization of [Ph₄Sb(OPyrMe)][OTf] ( 2 a ) and [Ph₄Sb(OPMe₃)][OTf] ( 2 b ), rare examples of structurally characterized complexes of stibonium acceptors. In contrast, 3 was found to engage a variety of Lewis bases, forming stable isolable complexes of the form [Ph₃Sb(donor)₂][OTf]₂ [donor=OPMe₃ ( 6 a ), OPCy₃ ( 6 b , Cy=cyclohexyl), OPPh₃ ( 6 c ), OPyrMe ( 6 d )], [Ph₃Sb(dmap)₂(OTf)][OTf] ( 6 e , dmap=4‐(dimethylamino)pyridine) and [Ph₃Sb(donor)(OTf)][OTf] [donor=1,10‐phenanthroline ( 7 a ) or 2,2′‐bipy ( 7 b , bipy=bipyridine)]. These compounds exhibit significant structural diversity in the solid‐state, and undergo ligand exchange reactions in line with their assignment as coordination complexes. Compound 3 did not form stable complexes with phosphine donors, with reactions instead leading to redox processes yielding SbPh₃ and products of phosphine oxidation.     

Occurrence of Volatile Metal and Metalloid Species in Landfill and Sewage Gases

Abstract

Speciation of volatile metals and metalloids in the environment is extensively described in literature. In order to investigate unstable volatile organometallics, on-line coupling of GC with ICP-MS was used. Preliminary results for gases of sewage sludge fermentation at thermophilic and mesophilic conditions are compared with the metal and metalloid speciation in landfill gases. In each case 20 L gas were sampled by cryogenic trapping. The species were identified by element-specific detection either by retention time of standards or by calculation of the boiling point correlation. Characteristic of the separation is the linear correlation of boiling point (bp/°C) versus retention time (rt/min) (bp = 6.39?rt -109.2, r² = 0.9926). The amounts of total volatile elements are estimated by semi-quantification. Cd, Sn. Hg, Pb (sewage gas) and Se, Te, Hg, Pb (landfill gas) were determined in the range of ng m^?3 level; As, Sb, Te and Bi (sewage gas) and As, Sn, Sb and Bi (landfill gas) in the μg m^?3 level range.     

ChemInform Abstract: The ′Sub′ Metallide Oxide Hydrides Sr21Si2O5H12+x and Ba21M2O5H12+x (M: Zn,Cd, Hg,In, Tl Si,Ge, Sn,Pb, As,Sb, Bi).

The title compounds are synthesized from melts of composition A:M:O:H = 21:2:5:24 (A: Sr, Ba; M: Zn, Cd, Hg, In, Tl Si, Ge, Sn, Pb, As, Sb, Bi) using BaH₂/SrH₂ as hydrogen sources.     

Systematic investigations of the multi-element preconcentration from copper by precipitation of the matrix as copper(I) oxide and copper(I) thiocyanate

Two methods for multi-element preconcentration from copper by reductive matrix precipitation are presented. In systematic investigations on the coprecipitation behaviour of Ag, Al, Au, Bi, Cd, Co, Cr, Fe, Ga, In, Mn, Mo, NJ, Pb, Sb, Se, Sn, Te and Zn during precipitation of the copper matrix as Cu₂O or CuSCN, the separation parameters were optimized. By combination with a hexamethyleneammonium hexamethylenedithiocarbamate collector precipitation, a concentration of 8 elements (Cu₂O precipitation) or 13 elements (CuSCN precipitation) in a small volume was achieved. The limits of detection of the procedures are, depending on the element, 0.1–5 μg g^?1 for flame atomic absorption spectrometry (AAS) and 0.01–0.1 μg g^?1 for graphite furnace AAS. The relative standard deviations are about 3%. The analytical performance of the procedures is compared with that of an electrolytic copper separation.     

Syntheses,Spectroscopic Studies,and Crystal Structures of Me2Sn(O2PPh2)2, Ph2Pb(O2PMe2)2, and Ph2Pb(O2PPh2)2

Me₂Sn(O₂PPh₂)₂ ( 1 ), Ph₂Pb(O₂PMe₂)₂ ( 2 ), and Ph₂Pb(O₂PPh₂)₂ ( 3 ) have been synthesized by the reactions of Me₂SnCl₂ or Ph₃PbCl with the corresponding diorganophosphinic acid in methanol. X‐ray diffraction studies show that the diorganophosphinate groups behave as double bridges between the metal atoms leading to polymeric ring‐chain structures with M₂O₄P₂ (M = Pb, Sn) eight‐membered rings. The organic groups bonded to the metal atoms are in trans‐position in the resulting octahedral arrangement around the metal atoms. The IR and the mass spectra were reported and discussed.     

Anodic stripping voltammetry of tellurium(IV) in aqueous solution and mixed solvents

The anodic stripping determination of Te(IV) using a rotating glassy carbon disc electrode is described. 0.1 ppm tellurium can be determined in 1 M HCl. Interfering effects of the metals forming intermetallic compounds with tellurium on the electrode are eliminated by solvent extraction. Te(IV) is determined either after its extraction — as an ion associate or as the chelate with diphenylthiocarbazone — in the organic phase which is adjusted for the stripping determination by the addition of methanolic solution of LiCl or after the separation of all interfering elements by an extraction procedure involving the extraction of Te(IV) into methylisobutylketone and back extraction of Te(IV) with water followed by the separation of the remaining interfering elements into diisopropylether. The proposed method enables the determination of 10 μg Te in the presence of 25 mg Pb and Sb and 0.5 mg Ag, Cu, Bi, As, Sn, Cd, Zn with reproducible results and error ±5%.     

Magnetic properties of RE5Ir2X (RE = Y,Gd–Ho,X = Sn,Sb, Pb,Bi) and magnetocaloric characterization of Gd5Ir2X

Systematic phase analytical studies of the systems RE-Ir-X (X = Sn, Pb, Sb, Bi) led to 15 new stannides, plumbides, antimonides and bismuthides with the composition RE₅Ir₂X. The compounds have been synthesized and characterized by X-ray powder diffraction. The structures of Gd₅Ir₂Sb and Dy₅Ir₂Bi have been refined from single crystal X-ray diffractometer data: Mo₅SiB₂ type, I4/mcm, a = 775.2(2), c = 1361.3(5) pm, wR2 = 0.0933, 404 F² values, 16 variables for Gd₅Ir₂Sb and a = 767.5(1), c = 1368.9(3) pm, wR2 = 0.0694, 571 F² values, 16 variables for Dy₅Ir₂Bi. Magnetic measurements of Gd₅Ir₂X (X = Sn, Pb, Sb, Bi), Tb₅Ir₂X (X = Sn, Pb, Sb, Bi), Dy₅Ir₂Pb, Dy₅Ir₂Bi and Ho₅Ir₂Pb indicate ferromagnetic transitions at T_C = 154.3, 159.3, 124.4, 119.3, 99.2, 98.2, 65.5, 68.6, 45.1, 35.6 and 23.5 K, respectively. Gd₅Ir₂Bi and Gd₅Ir₂Sb show an additional antiferromagnetic transition at T_N = 118.5 and 91.0 K. The magnetocaloric effect of Gd₅Ir₂X (X = Sn, Pb, Sb, Bi) in terms of the isothermal entropy change ΔS_m is −7.3(3), –6.5(3), –8.7(3) and −9.0(3) J kg⁻¹ K⁻¹ at temperatures of 153, 157, 120 and 126 K for a 5 T field change. ¹¹⁹Sn Mössbauer spectra of Gd₅Ir₂Sn at 78 K show a huge transferred hyperfine field of 21.9(1) T and an isomer shift of 1.94(1) mm s⁻¹, typical for stannides. ¹²¹Sb Mössbauer spectra of Gd₅Ir₂Sb at 78 K show a transferred hyperfine field of 14.2(3) T and an isomer shift of −7.45(8) mm s⁻¹ reflecting the antimonide character.     

Interferences of hydride forming elements and of mercury in the determination of antimony, arsenic, selenium and tin by hydride-generation AAS

Summary By means of the radiotracer technique supplemented by conventional absorption measurements, the interferences of As, Bi, Hg, Pb, Sb, Se, Sn and Te in amounts between 10 g and 1 mg with the determination of As, Sb, Se and Sn by hydride generation AAS using heated quartz tube were investigated during the hydride-generation and the atomization stages. Amounts up to 100 g of Hg and Pb do not cause any detectable interference. The interference of Bi and Te is dominant in the hydride-generation stage and that of As, Se, Sb and Sn in the atomization stage. Tin is retained to a considerable extent in the quartz tube and the resulting memory effect makes the determination of As, Sb, and Se impossible. In the absence of interfering elements, the efficiency of the formation of hydrides of As, Sb, Se and Sn was close to 100%. However, a reduction of Sb(V) to Sb(III) prior to the hydride-generation is necessary for which an improved procedure was developed.

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Störungen von Hydridbildnern und von Quecksilber bei der Bestimmung von Antimon, Arsen, Selen und Zinn durch die Hydrid-AAS

Zusammenfassung Mittels der Radiotracertechnik und Atomabsorptionsspektrometrie wurde der Störeinfluß unterschiedlicher Mengen (10–1000 g) von As, Bi, Hg, Pb, Sb, Se, Sn und Te auf die Bestimmung von As, Sb, Se und Sn mit der Hydrid-AAS untersucht. Durch diese Verfahrenskombination war es möglich, das Ausmaß der Störungen durch diese Elemente sowohl im Hydrierungs- als auch im Atomisierungsschritt zu bestimmen sowie zum großen Teil auch die Gründe für ihr Auftreten aufzuklären. Keine nachweisbare Störung verursachen Hg und Pb bis zu jeweils 100 g. Die Störung durch Bi und Te tritt hauptsächlich im Hydrierungsgefäß auf, hingegen die durch As, Sb, Se und Sn im wesentlichen in der Quarzabsorptionszelle. Bei Zinn wurde ein starker Memoryeffekt festgestellt, der aus der Ablagerung dieses Elements in der Quarzküvette resultiert und der die Bestimmung von As, Sb und Se völlig unmöglich macht. Ohne diese Störelemente liegen die Hydrierungsausbeuten für As, Sb, Se und Sn bei nahezu 100%. Bei Antimon ist allerdings eine vorherige Reduktion von Sb(V) zu Sb(III) notwendig, für die ein verbessertes Verfahren vorgeschlagen wurde. Denn durch die Radiotracertechnik konnte nachgewiesen werden, daß die während der Alterung von Sb(V)-Lösungen durch Kondensationsprozesse entstehenden Polysäuren nicht mehr hydriert werden können.