Paramagnetic Analysis

Paramagnetic oxygen analyzers (Firma Mayhac, Hamburg) allowed Brunnho-fer et al. (1968 a, b) and Marcelle (1975) to measure oxygen exchange of whole CAM plants continuously over complete diurnal cycles. These authors showed 

Kalanchoe daigremontiana, temperature 20° C (modified after Brunnhofer et al, 1968 a) 

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Samples of the exit gas were withdrawn through 3.2-mm quartz tubing at about 0.8 cm /sec. The gas passed through a condenser, a water trap, a tube containing Drierite, and a vacuum pump and was collected in a Teflon bag for analysis. CO and CO2 were determined by non-dispersive infrared, O2 by paramagnetic analysis, NO, by chemiluminescence, and hydrocarbons by flame ionization. N2 and H2O were calculated from stoichiometry. 

More P J 1989 Analysis of polarized electron paramagnetic resonance spectra Advanced EPR Applications In Biology and Biochemistry ed A J Hoff (Amsterdam Elsevier) ch 12... 

Mounting electrodes in a bioreactor is costly, and there is an additional contamination risk for sensitive cell cultures. Some other sensors of prac ticai importance are those for dissolved oxygen and for dissolved carbon dioxide. The analysis of gas exiting from a bioreactor with an infrared unit that detects carbon dioxide or a paramagnetic unit that detects oxygen (after carbon dioxide removal) has been replaced by mass spec trophotometry. Gas chromatographic procedures coupled with a mass spectrophotometer will detect 1 the volatile components. 

The product is a black-brown solid that is very sensitive to oxygen. The same cation can be obtained by oxidation of S4N4 with AsFs and is unusual in being the only sulfur-nitrogen (paramagnetic) radical that has been obtained as a stable crystalline salt. X-ray diffraction analysis shows the structure to be a planar 5-membered ring with approximate... 

The applications of EPR spectroscopy reviewed in the present chapter are based on the sensitivity of the spectrum displayed by iron-sulfur centers to various characteristics, such as the redox state of the center, the distribution of the valences on the iron ions, the nature and the geometry of the ligands, and the presence of nearby paramagnetic species. Although considerable progress has been made during the past few years in the quantitative analysis of these various effects in the case of the conventional iron-sulfur centers described in Section II, the discovery of centers exhibiting unusual EPR properties as... 

Compared with the extensive application of NMR procedures, electron paramagnetic resonance (EPR) is used less frequently except for analysis of the state of metals in enzymes and coenzymes. There has, however, been increasing awareness of the role of radical-mediated reactions and some examples are used to illustrate its potential. 

The ESR measurements were made at RT or 77 K on a Varian E-9 spectrometer (X-band), equipped with an on-line computer for data analysis. Spin-Hamiltonian parameters (g and A values) were obtained from calculated spectra using the program SIM14 A [26]. The absolute concentration of the paramagnetic species was determined from the integrated area of the spectra. Values of g were determined using as reference the sharp peak at g = 2.0008 of the E i center (marked with an asterisk in Fig. 3) the center was formed by UV irradiation of the silica dewar used as sample holder. 

The spin-Hamiltonian concept, as proposed by Van Vleck [79], was introduced to EPR spectroscopy by Pryce [50, 74] and others [75, 80, 81]. H. H. Wickmann was the first to simulate paramagnetic Mossbauer spectra [82, 83], and E. Miinck and P. Debmnner published the first computer routine for magnetically split Mossbauer spectra [84] which then became the basis of other simulation packages [85]. Concise introductions to the related modem EPR techniques can be found in the book by Schweiger and Jeschke [86]. Magnetic susceptibility is covered in textbooks on molecular magnetism [87-89]. An introduction to MCD spectroscopy is provided by [90-92]. Various aspects of the analysis of applied-field Mossbauer spectra of paramagnetic systems have been covered by a number of articles and reviews in the past [93-100]. 

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