Semiconductor gas sensors in bioreactor control

A simple semiconductor gas sensor (TGS 812) is used for the on-line measurement and control of indole during the production of l-tryptophan from indole and l-serine with immobilized E. coli cells. Indole is estimated in the reactor gas space. In combination with an automatic indole supply system, a feed-batch process became possible. The indole concentration was monitored and kept within the optimal range (300–600 mg l^?1). A simple gas-sensing electrode dipped in the reaction medium provides direct measurement of organic solvents and gases in the liquid. Such a system is suitable for on-line determination of ethanol (10–70 g l^?1) during continuous production of ethanol with immobilized yeast cells.     

Impedance laser spectroscopy in a small RF-excited neon discharge

Laser impedance spectroscopy in a miniature neon RF-discharge operating at 0.27 bar was performed. The dominant role of the metastable atoms to the size and the sign of the RF-signal was investigated. Excellent linearity of the RF-signal but poor detection sensitivity of excited metastable neon atoms were found at low laser powers.     

Synthese und Struktur von [(Ph3PAu)3NPPh3][PF6]2, einem Gold(I)‐phosphoraniminato‐Komplex

Synthesis and Crystal Structure of [(Ph₃PAu)₃NPPh₃][PF₆]₂, a Gold(I) Phosphoraneiminato Complex The photolytic reaction of Ph₃PAuN₃ with Cr(CO)₆ in THF yields the phosphoraneiminato complex [(Ph₃PAu)₃NPPh₃]²⁺ in low yield as well as the cluster cation [(Ph₃PAu)₈]²⁺ as the main product. The phosphoraneiminato complex crystallizes from CH₂Cl₂ with [PF₆]^? ions as [(Ph₃PAu)₃NPPh₃][PF₆]₂·CH₂Cl₂ in the triclinic space group with a = 1200.8(1), b = 1495.6(2), 2053.5(5), α = 86.97(2)°, β = 82.79(1)°, γ = 81.87(2)°, and Z = 2. The phosphoraneiminato ligand bridges through its N atom three Au atoms, which itself are connected to each other by weak aurophilic interactions.     

Tetragonal low-temperature structure of LiAl

The cubic face-centered structure of LiAl (, at ) transforms into a tetragonal body-centered structure (I4₁/amd, , at ). This first-order phase transition at about during heating is probably the reason for the so-called “ anomalies” in some physical properties like specific heat, electrical resistivity and nuclear-spin lattice relaxation. This transition seems to be correlated with the composition Li:Al of the alloy and the amount of Li vacancies.     

Binucleare Nickel(0)-Komplexe mit „Schlangenliganden”︁ vom 1-Azadientyp: Modellsysteme der oxidativen Kopplung von 1-Azadienen und 1,3-Dienen am Nickel(0)

Binuclear Nickel(0) Complexes with “Snake Ligands” of 1-Azadiene Type: Model Systems of the Oxidative Coupling of 1-Azadienes and 1.3-Dienes at Nickel(0) Synthesis, properties, and reactions of dimeric nickel(0) complexes with special 1-azadiene typ ligands (“snake ligands”) are described. The X-ray analysis of a typical compound (Bis-(bis-cinnamaldehyde-N,N'-propylendiimine)-dinickel(0)) shows that both central atoms have the coordination number 3. The four 1-azadiene groups are coordinated in a different way: unidendate coordination by N-Ni(1) bond and bidendate coordination by N-Ni(1) and olefine-Ni(2) bond. The compound is a good model system for the oxidative coupling reaction of 1-azadienes with 1.3-dienes at 2 nickel(0) centres. IR and electronic spectra show other complexes with this type of ligands to have an analogous coordination sphere.     

Beiträge zur Chemie der Silicium—Stickstoff-Verbindungen, 21. Mitt.

Zusammenfassung Durch Umsetzung von Disilbercyanamid mit Organyl- und Alkoxy-halogensilanen wurden 9 bisher unbekannte zweifach silylsubstituierte Carbodiimide der Stoffgruppen (R₃SiN)₂C, [(RO)₃SiN]₂C, (R₂RSiN)₂C und R₃SiNCNSiR₃ dargestellt und in ihrer Struktur über¹⁴N- und¹H-kernmagnetische Resonanzmessungen, IR- und Raman-Spektren eindeutig als Carbodiimidderivate aufgeklärt.20. Mitt.:U. Wannagat undH. Kuckertz, Angew. Chem.75, 95 (1963).Zugleich 2. Mitt. über silylsubstituierte Carbodiimide; 1. Mitt.J. Pump undU. Wannagat, Ann. Chem.652, 21 (1962); Angew. Chem.74, 117 (1962); Österr. Chemiker-Ztg.62, 319 (1961).     

Thin-layer chromatography combined with diode laser desorption/atmospheric pressure chemical ionization mass spectrometry

The desorption of an analyte by a continuous wave diode laser from a porous surface of a thin-layer plate covered with a graphite suspension is presented. The thermally desorbed analyte molecules are ionized in the gas phase by a corona discharge at atmospheric pressure. Therefore, both essential processes--the desorption and the ionization of analyte molecules, which are often performed in one step--are separated. The target preparation is easy and fast since no additional extraction process is required. The mass spectrometric background signal was mostly limited to the low mass range showing no interference with typical compounds of interest. In this study, the calmative and antihypertensive drug reserpine was chosen as model analyte, which is often used for specification of mass spectrometers. No fragmentation was observed because of efficient collisional cooling under atmospheric pressure. The influence of diode laser power and the composition of the graphite suspension were investigated, and a primary optimization was performed.