Element-selective trace detection of toxic species in environmental samples using chromatographic techniques and derivative diode laser absorption spectrometry

-7 absorption per square root of detection bandwidth are obtained if sufficient laser power is available and if the absorption is also subject to additional modulation. The analytical versatility of these techniques is demonstrated by quantitative analysis of very low concentrations of (i) Cr(VI) species in tap water and (ii) chlorinated poly-aromatics (chlorophenols) in plant extracts, both after chromatographic separation. The atomic absorption measurements were performed in an air–acetylene flame (Cr) and in a low-pressure microwave-induced plasma (chlorophenols). Received: 2 April 1998     

Mikroanalyse von Eisen und Stahl. I. Silicium

Zusammenfassung Es wird ein Verfahren zur mikroanalytischen Bestimmung von Silicium in Eisen und Stahl mit Einwaagen von 10 bis 100 mg beschrieben. Das Silicium wird photometrisch als Silikomolybdänsäure bestimmt. Der Zeitbedarf für eine Einzelbestimmung beträgt etwa 25 Minuten, der relative Fehler im Mittel ±1 bis 2%.

---

Summary A method is described for the microanalytical determination of silicon in iron and steel with samples from 10 to 100 mg. The silicon is determined photometrically as silicomolybdic acid. The time required for a single determination is around 25 minutes; the relative error is ± 1 to 2%.

---

Résumé On décrit un procédé de dosage micro-analytique du silicium dans le fer et dans l'acier sur des prises d'essai de 10 à 100 mg. On dose le silicium par photométrie à l'état d'acide silicomolybdique. La durée d'un seul dosage est d'environ 25 minutes, l'erreur relative ± 1 à 2% en moyenne.

     

The nuclear structure of198Au from the reaction197Au(n, γ)198Au

Precise energies and intensities of about 450γ-rays of the¹⁹⁷Au(n, γ)¹⁹⁸Au reaction have been investigated in the energy range from 30 keV to 1 MeV with a bentcrystal spectrometer. Prompt and delayedγ-γ coincidences have been studied with Ge(Li) detectors. A half-life of 124±4 ns has been measured for the state at 312.036 keV, which is found to decay to the ground state through the cascade 97.195–214.841 keV. A new level scheme based on these results has been constructed which contains 160 transitions. Spin and parity assignments have been made for most of the levels.     

Fine structure at the carbon 1s K edge in vapours of simple hydrocarbons

Electron yield spectra in the range of 280 ? ?ω ? 300 eV which basically resemble the absorption spectra, have been measured for gaseous methane, ethane, ethylene, benzene and acetylene using synchrotron radiation. The spectra being fairly simple compared to the valence shell absorption are characterized by weak maxima for energies below the ionization threshold for C 1s for methane and ethane whereas additional strong resonances are observed in the spectra from molecules containing π-electrons. The nature of these excitations is discussed on the basis of their term values using information from XPS-measurements.     

Polyurethane foams as selective sorbents for noble metals : Quantitative extraction and separation of rhodium from iridium in hydrochloric acid containing tin(II) chloride

The distribution of rhodium(III) between polyether-type polyurethane foam and 0.5–5.0 mol dm^?3 hydrochloric acid in the presence of small amounts of tin(II) chloride is described. The distribution of rhodium is affected by the extraction temperature, acid concentration and the Sn(II):Rh ratio. The capacity of the polyurethane foam for rhodium is in excess of 0.5 mmol g^?1. Rhodium is presumably sorbed in the form of a chloro(trichlorostannato)rhodium(III/I) complex anion. Iridium is not extracted by the foam under corresponding conditions and can be separated quantitatively from rhodium.     

Microscopic theory of laser gain in semiconductor quantum wells

Received: 31 October 1997/Accepted: 31 October 1997