The determination of tellurium by nondispersive atomic fluorescence spectrometry using the hydride generation technique

Atomic fluorescence spectrometry with a nondispersive measuring system is combined with a hydride generation technique for the determination of tellurium. Atomic fluorescence measurement is based on the reduction of tellurium by either metallic zinc or sodium borohydride, introduction of the generated tellurium hydride into a premixed argon (entrained air)-hydrogen flame, and excitation with a tellurium electrodeless discharge lamp. The comparison of the zinc and the sodium borohydride reduction methods is discussed in terms of detection limit, precision and interference. The best attainable detection limits for tellurium are 2ng (0.1 $\text{ng}\text{ml}$) and 30 ng (1.5 $\text{ng}\text{ml}$) with the zinc and the sodium borohydride methods respectively. Analytical working curves obtained from peak-height and peak-area measurements are linear over a range of approximately 4 orders of magnitude. Of the mineral acids examined in the range up to 2.0 m. nitric acid gives a depressing interference in the range greater than 0.5 m in the zinc method, whereas all of the acids greater than 1.0 m give a slight enhancement of the signal in the sodium borohydride method. The presence of several elements including other hydride-forming elements in 1000-fold ratio to tellurium causes a depressing interference, while enhancing interferences from tungsten and vanadium are observed in the zinc and the sodium borohydride methods, respectively. The present system coupled with the zinc method has been applied to the determination of tellurium in several samples of high-purity copper metal after separation of the analyte from copper by passing an ammoniacal solution of the sample through Chelex-100 resin. The results are in good agreement with those obtained by graphite furnace atomic absorption spectrometry.     

Photochemistry of 5.6-epoxy-1,3-dienes : Influence of a 7-hydroxy substituent

Triplet sensitization of the 7-hydroxy-5,6-epoxy-1,3-diene 10 causes cleavage of the C(5),0 epoxide bond followed by the formation of the three isomers 11–13 or induces scission of the C(6), C(7) bond followed by the formation of the aldehyde 14 and the bicyclo[3.2.0]heptanols 15 and 16. However, irradiation of the corresponding acetate 18 gives only C(5),0 epoxide bond scission (18 → f) followed by the cyclization process f → 19, the 1,2-Me shifts f → 20, 21 and the γ-H abstraction f → g leading to the cyclopropane formation g → 22.     

The extraction of niobium (V) and Tantalum (V) by Octylarsinic acid in chloroform

Dioctylarsinic acid (HDOAA) in chloroform solution extracts Nb(V) and Ta(V) efficiently from solutions containing oxalate and oxalic acid at hydrochloric acid concentrations greater than 1M.The extraction coefficients are 92.5 at 7M hydrochloric acid and 251 at 6M hydrochloric acid for niobium and tantalum, respectively. These metals can be extracted even more efficiently from sulfuric acid solutions. The results of the reagent- and pH-dependence studies suggested that a trimeric, monobasic oxoacid of niobium, associated with ten HDOAA molecules, is extracted. Tantalum appears to be present in the organic phase as (H₂DOAA)⁺ [Ta(C₂O₄)₃ (HDOAA_n] (n=l or 2).     

Differential determination of arsenic(III) and arsenic(V), and antimony(III) and antimony(V) by hydride generation-atomic absorption spectrophotometry,and its application to the determination of these species in sea water

A method is described for the differential determination of As(III) and As(V). and Sb(III) and Sb(V) by hydride generation-atomic absorption spectrophotometry with hydrogen-nitrogen flame using sodium borohydride solution as a reductant. For the determination of As(III) and Sb(III), most of the elements, other than Ag⁺, Cu²⁺, Sn²⁺, Se⁴⁺ and Te⁴⁺, do not interfere in an at least 30,000 fold excess with respect to As(III) or Sb(III). This method was applied to the determination of these species in sea water and it was found that a sample size of only 100 ml is enough to determine them with a precision of 1.5–2.5%. Analytical results for surface sea water of Hiroshima Bay were 0.72 μgl^?1, 0.27 μgl^?1 and 0.22 μgl^?1 for As(total), As(III) and Sb(total), respectively, but Sb(III) was not detected in the present sample. The effect of acidification on storage was also examined.     

Determination of ten trace elements in meteorites and lunar materials by radiochemical neutron activation analysis

A procedure is reported for the determination of Ni, Ge, Ru, Au, Ir, Zn, Ga, Cd, In and U in meteorites and lunar materials. The precision in multiple determinations at the 95% confidence level is less than 10% except for gold (15%). Ruthenium and uranium are determined by counting ⁹⁷Ru and ¹⁰³Ru x-rays; the chemical yield is determined from ¹⁰⁶Ru added before sample dissolution. The activity of ^116mIn is determined with improved sensitivity from integral counts in the region 1.5–3.0 MeV on a NaI(TI) detector.     

Determination of fluorine in standard rocks by photon activation analysis

A highly sensitive determination of fluorine in standard rocks by photon activation using the¹⁹F(,n)¹⁸F reaction combined with pyrohydrolysis for the separation of¹⁸F has been reported. The irradiation energy was operated at 20 MeV to avoid the interference from Na, because Na is one of the major element in rocks and¹⁸F is also produced from Na via²³Na(,n)¹⁸F reaction above its threshold energy, 20.9 MeV. After irradiation, fluorine was extracted by pyrohydrolysis and separated as LaF₃ precipitate. It was ascertained that the average recovery of fluorine in standard rocks was about 90% and the precipitate was of high radiochemical purity. This method was applied to the analysis of ten GSJ rock reference samples and two USGS standard rocks issued by the Geological Survey of Japan and the United States Geological Survey, respectively. The detection limit of this method was 0.02 g/g, and the results obtained by this method were in good agreement with the recommended values. This method was easily applied to the determination of a few ppm level of fluorine in rock samples, such as ultrabasic rock and feldspar.     

The precise and accurate determination of silicon in rocks by 14-MeV neutron activation analysis

The errors associated with the measurement of silicon in silicate rocks by fast neutron activation analysis have been investigated. The accuracy has been determined by comparing the values obtained with the accepted values for 22 silicate rock standards. Precisions of 0.25 % and accuracies of about 0.45 % are possible.     

Determination of manganese(II) in powdered barnacle shells by electron paramagnetic resonance

A rapid precise method of determining Mn(II) (as opposed to total manganese) in powdered barnacle shells by e.p.r. is described. The method is based on the linear relationships between the intensity of the first-derivative e.p.r. signal and the weight and Mn(II) concentration in the sample. Atomic absorption was used as a reference method. For eleven samples, the difference between the a.a.s. and e.p.r. methods was, on average, within 3 %; the detection limit was 20 p.p.b. A good correlation between the Mn(II) content of the shell and the position of the animal in an inter-tidal zone was found.     

Studies on metal carboxylates: XI. Reactions of rhenium carbonyl with picolinic acid and of the tungsten(I) complex [W(CO)3(pic)]n with monodentate tertiary phosphines

The reactions of the tungsten(I) complex of picolinic acid [W(CO)₃(pic)]_n with certain monodentate tertiary phosphines affords a convenient route to complexes of the types W(CO)₃(PR₃)₃ and HW(CO)₂(PR₃)₂(pic). The latter hydrido complexes of tungsten(II) have been characterized by infrared and NMR spectroscopy. The reactions of Re₂(CO)₁₀ with picolinic acid have also been investigated and the new series of rhenium(I) derivatives of the types Re(CO)₃(L)(pic), where L = py, 4-Ph-py, PPh₃ or dppe, and Re(CO)₂(L')₂(pic), where L' = PPh₃ or $\text{1}\text{2}$dppe, have been isolated and characterized.     

Spectrophotometric determination of manganese utilizing metal ion substitution in the cadmium-α,β,-γ,δ -tetrakis(4-carboxyphenyl)porphine complex

Manganese(II) reacts quickly with α, β, γ, δ-tetrakis(4-carboxyphenyl)porphine [T(4-CP)P] at room temperature by metal substitution with a cadmium—T(4-CP)P complex in weakly alkaline medium containing imidazole. Oxidation by dissolved oxygen gives a manganese(III) complex having the Soret band at 469 nm. This forms the basis of a spectrophotometric method for the determination of manganese in the range 25–560 μg l^-1. The sensitivity (0.001 absorbance) is 0.56 ng cm^-2. Interferences of 17 cations and 8 anions were examined; only Cu²⁺, Co²⁺, Cr³⁺ and Pb²⁺ interfered markedly. The method was successfully applied to the determination of manganese in tea leaves.     

Flow enthalpimetric determination of glucose, based on oxidation by 1,4-benzoquinone and use of an immobilized glucose oxidase column

A flow enthalpimetric method for the determination of glucose is presented. The method is based on the reaction of glucose with 1,4-benzoquinone in the presence of immobilized glucose oxidase. d-Glucose concentrations ranging from 0.02 to 75mM can be determined. The method is applicable to the determination of glucose in soft drinks, wines, beers, jams and serum.     

Calorimetric and spectroscopic studies of the critical phase transition in (CH3NH3)2[SnCl6]

(CH₃NH₃)₂[SnCl₆] undergoes a critical phase transition at 154.32 ± 0.06 K with the critical exponents α = 0.36 ± 0.04, α' = 0.19 ± 0.02, the critical entropy ratio 0.062 and the total transition entropy (1.60 ± 0.18) R. Infrared spectral change favors the order-disorder mechanism of the transition proposed from the thermodynamic data.     

Assignment of photoelectro bands for naphthalene and anthracene by penning ionization electron spectroscopy

The Ne¹(³P₂) Penning electron spectra and the Ne I photoelectron spectra were measured in the gas phase. The observed systematic differences in their relative intensities were interpreted in terms of the electron distributions of the relevant molecular orbitals and used for assignment of the deep π bands, π₁ (12.4 eV) for naphthalene, and π₂ (11.9 eV) and π₁ (12.8 eV) for anthracene.     

Molecular structure of carbonyl fluoride as studied by gas electron diffraction and microwave data

The molecular structure of carbonyl fluoride has been determined by electron diffraction. The results have been used in conjunction with the rotational constants reported by Carpenter in a combined structure analysis. The values so obtained are r_z (C=O) = 1.1717 ± 0.0013 Å, r_z (C-F) = 1.3157 ± 0.0005 Å, and ∠_zF-C-F = 107.71 ± 0.08°. These agree with the corresponding parameters estimated by Carpenter from the rotational constants alone. The effective constants, α₃, representing the cubic anharmonicity of bond stretching vibrations have been estimated.     

New synthesis of β-lactams

α-Methylene-β-lactams 3 were synthesized from the various 2-bromoallylamine derivatives 2 using a catalytic amount of Pd(OAc)₂ or PD(acac)₂ and PPh₃, under 1–4 atom pressure of CO in good yields. Similarly, α-alkylidene-β-lactams 20 were synthesized from 3-alkyl-2-bromoallylamines 19, which were easily prepared from the olefins 14, in the same manner.     

Determination of submicrogram amounts of selenium(IV) by means of the catalytic reduction of 1,4,6,ii-tetraaza- naphthacene

In the presence of glyoxal and hypophosphorous acid 1,4,6II-tetraazanaph-thacene is reduced to I,6-dihydro-I,4,6,II-tetraazanaphthacene. The reaction is catalyzed by selenium(IV). By means of this catalytic reaction, submicrogram amounts of selenium(IV) can easily be determined. The method is simple and sensitive, and there are few interferences.     

Application of multiconfigurational many-body perturbation theory to the calculation of ionization potentials,electron affinities and excitation energ

Multiconfigurational many-body perturbation theory is applied to the problem of calculating ionization potentials, electron affinities, and excitation energies. H₂O, C₂H₄, and H₂ are studied, with correlation corrections through third order and inclusive of certain higher-order terms. Results are compared with those by other many-body theoretical methods.     

Cation analysis by thin-layer chromatography and reflectance spectroscopy : Part II. The determination of copper,nickel and zinc

A method has been developed whereby micro quantities of copper, nickel and zinc resolved on cellulose chromatoplates can be analyzed in situ by means of reflectance spectroscopy. Copper and nickel were determined in the presence of 11 other cations without any interference by employing neocuproine and dimethylglyoxime, respectively, as chromogenic reagents. In the case of zinc, the use of 3,3'-dimethyl-naphthidine was equally successful except in the presence of tin, cadmium and iron. Deviations to be expected when the procedure is employed routinely to determine nickel, copper and zinc, were estimated to be 2.1, 2.8 and 5.6%, respectively.     

Tautomerism in monothio-β-diketones studied by PMR and quantum chemical calculations

It is shown by proton NMR and quantum chemical PCILO calculations that monothio-β-ketones

in solution exist as different isomers depending on substituents, solvent and temperature. In solvents with low dielectric constants the hydrogen-bridged cis enol form predominates, and is in fast equilibrium (in the NMR scale) with nonchelated trans enol forms down to ?100°C at least. Transition enthalpies are of the order of 7–15 kJ mol^?1. In compounds with R₂ = Me the rotation of the Me -CS group around the neighbouring C-C- bond can be detected and the thermodynamic and kinetic parameters estimated. The reason for the slowing down of this rotation, inferred from the line broadening in NMR, is probably the stabilization of a trans isomer by interaction between the protons of the methyl group and the lone pairs of the oxygen atom. There are no indications for the presence of chelated and non-chelated enethiol isomers from the PMR studies and quantum chemical calculations performed.