The use of optical emission spectrometry with microwave induced plasma (MIP) discharges in a surfatron combined to different types of hydride generation for the determination of arsenic

The stability and analytical figures of merit of argon microwave induced plasma (MIP) discharges in a surfatron as sources for optical emission spectrometry (OES) are described. These MIPs have been used for the determination of arsenic after hydride generation. They could cope with the excess of hydrogen developed during the hydride generation step and thus not necessitated an isolation of the hydrides before releasing them into the MIP. Two methods for the generation of the volatile AsH₃ were applied. First a micro method was used with solid NaBH₄ on which 10 1 of the acidified sample solution is transferred. Its capabilities were compared to those of continuous hydride generation using a 5% (w/w) NaBH₄-solution and continuous liquid removal in a flow cell. Both methods were optimized for an argon MIP operated at a power of 120–160 W and gas flows of 20 l/h Ar. In the case of solid NaBH₄ the detection limit for As has been found to be 1.0 g/ml (10 ng) and with the flow cell hydride generation 50 ng/ml. The calibration curves are linear over three orders of magnitude. Interferences caused by Sb, Fe, Sn and NaCl were investigated. No interferences occurred for Sb up to an interferent concentration of 250 g/ml. The presence of Fe causes a significant depression of the As signal whereas an increase of the As signal was observed in the case of Sn. High NaCl concentrations did not influence the As signals when using continuous hydride generation, but had a great influence when using solid NaBH₄.     

Ein neues Cobaltat mit Inselstruktur: Li6[CoO4]

A New Cobaltate with Isolated Anion Structure: Li₆[CoO₄] For the first time transparent, blue single crystals of Li₆[CoO₄] have been prepared (Li₂O/Na₂O/?CoO”? (Li:Na:Co = 1.3:1.3:1), Co-tube, 580°C, 22 d). Corresponding to Li₆□CoO; it is an ordered variant of the Li₂O-type of structure: P4₂/nmc; a = 653.6(1) pm, c = 465.4(1) pm; Z = 2; d_x = 2.75 g cm^?3, d_pyk = 2.71 g cm^?3 (4-circle-diffractometer-data (PW 1100), AgKα; 230 from 936 I₀(hkl); R = 9.58%, R_W = 5.25%). Parameters see text. The Madelung Part of Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, these via Mean Fictive Ionic Radii, MEFIR, are calculated and discussed. The magnetic properties are measured in the temperature range of 14–297 K.     

Neues über Oxoferrate(III). I. Zur Kenntnis von Li5FeO4 [1] Mit einer Notiz über Mischkristalle Na5Fe1−xGaxO4

News on Oxoferrates(III). I. On Li₅FeO₄ (with a Remark on Na₅Fe_1?xGa_xO₄ Solid Solutions) For the first time transparent dark yellow single crystals of Li₅FeO₄, corresponding to Li₅□₂FeO₄ an ordered variant of the Na₂O-type of structure, are prepared [by mixtures of Li₂O and α-NaFeO₂ with Li:Na:Fe = 6:1:1, sealed Ag-cylinders, 700°C, 16 d]. Li₅FeO₄ is isostructural with Li₅GaO₄: a = 921.8(1), b = 921.3(1), c = 915.9(1) pm, Z = 8 [space group: Pbca, 4-circlediffractometer data, 2525 I₀ (hkl), R = 9.58% and R_w = 5.85%, d_pyk = 2.60 and d_x = 2.64 gcm^?3, parameters see text]. The Madelung Part of Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, these via Mean Effective Ionic Radii, MEFIR, are calculated and discussed. The magnetic properties are measured in the temperature range of 3.9–251.3 K.     

Neue Oxoferrate(III). Na2Li3[FeO4] und K2Li3[FeO4]

New Oxoferrates (III). Na₂Li₃[FeO₄] and K₂Li₃[FeO₄] . Na₂Li₃[FeO₄] and K₂Li₃[FeO₄] (transparent, pink or light yellow single crystals) have been prepared by heating mixtures of the oxides (Na:Li:Fe = 2.2:3.3:1; Ag-tube, 720°C, 27 d or K:Li:Fe = 2.2:3.3:1; analogous, 700°C, 40 d). Na₂Li₃[FeO₄] is isotypic with Na₂Li₃[GaO₄] (a = 832.2(1), b = 796.0(1), c = 656.3(1)pm, Pnnm) and K₂Li₃[FeO₄] with K₂Li₃[GaO₄] (a = 557.7(1), b = 880.6(1), c = 1101.8(2)pm, β = 111.51(2)°, P2₁/c). Four cycle diffractometer data: MoK_α, 525 out of 686 I₀(hkl), R = 9.36%, R_w = 5.97% or 1424 out of 1424 I₀(hkl), R = 8.45%, R_w = 5.66%. Parameters see text. The structures are characterized by calculations of the Madelung Part of Lattice Energy, MAPLE. The Effective Coordination Numbers, ECoN, which are calculated by means of Mean Fictive Ionic Radii, MEFIR, are compared with the analogous gallates.