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Solid-state NMR provides unique possibilities to study insoluble or noncrystalline molecules at the atomic level. High-resolution conditions can be established by employing magic-angle spinning at ultrahigh magnetic fields. We discuss NMR methods that make use of these experimental improvements and allow for the study of multiply or uniformly [¹³C,¹⁵N]-labeled polypeptides and proteins. Recent biophysical applications are reviewed.

Continuous environmental air monitoring is possible with open-path FTIR spectroscopy. Efficient chemometric tools are needed for the identification of unknown compounds that are observable in remote sensing of volatile emissions into the atmosphere. A qualitative analysis using spectra recorded at a resolution of 0.2 cm⁻¹is proposed, based on the cross-correlation function and calculated with data from component-specific intervals from library absorbance spectra. The characteristic wave-number intervals were selected on the grounds of the most intense component absorption bands for which negligible overlap was present with atmospheric absorption lines. The algorithm has been implemented for 36 different gaseous substances into an expert system for the evaluation of atmospheric FTIR spectra, recorded for routine work in active open-path monitoring. Detection limits for substance identification from mixture spectra are discussed. The influence from overlapping spectral features of co-existing atmospheric compounds can be reduced by preprocessing, including such techniques as scaled absorbance subtraction with appropriate spectra of the known gases. A discussion of identification strategies previously presented in the literature is included. © 2001 John Wiley & Sons, Inc. Field Analyt Chem Technol 5: 50–59, 2001

FTIR spectroscopy has been established for the monitoring of diffuse emissions into the open atmosphere. The method of choice for the evaluation of the atmospheric spectra uses the fitting of reference spectra by classical least squares. Important refinements can be achieved by selecting the optimal wavelength ranges based on objective mathematical criteria, improved spectral background strategies, and high-quality reference spectra that allow for the adaptation of nonlinearity effects. Under these improved conditions, new detection limits for atmospheric trace components are presented. The chemometric tools developed were integrated into an expert system, affording the evaluation of the atmospheric spectra with a minimum of user interaction. Results from several field campaign measurements within a municipal waste-treatment plant are presented, illustrating the reliability of the methods applied. Furthermore, extensive trace-gas concentration data were collected simultaneously with two FTIR spectrometer systems under various meteorological conditions and spatial scenarios for dispersion modeling of diffuse emissions from different sites. Emission rates of ammonia area sources were determined from path-integrated spectroscopic remote measurements and inverse dispersion modeling based on Lagrangian model calculations. The results were obtained within a factor of 1.4 times the actual emission rate values. © 2001 John Wiley & Sons, Inc. Field Analyt Chem Technol 5: 13–28, 2001

Improvements in the quantitative evaluation of atmospheric Fourier-transform infrared (FTIR) spectra, obtained in environmental monitoring by using a bistatic spectrometer setup, are presented. Preprocessing of interferograms and spectral data was carried out to improve the photometric accuracy and wave-number scale reproducibility, necessary for reliable quantitative analysis. Univariate component analysis was optimized, and a refined strategy for multivariate analysis by least squares was set up. Special procedures were developed for the determination of benzene and of small molecules with resolved rotation–vibration fine structure. Results from field measurements, which were obtained by using the implemented subroutines for univariate and multivariate spectrum evaluation, are presented and discussed. © 1999 John Wiley & Sons, Inc. Field Analyt Chem Technol 3: 141–159, 1999

Infrared rotatory dispersion (IRD) spectra of induced cholesteric phases resulting from solutions with liquid crystals as solvent can be used in the investigation of optically active compounds. The resolution enhancement for the so-called A-Cotton effects at the absorption bands of the originally nematic solvent by Fourier deconvolution is studied for these IRD spectra. The theoretical basis of the algorithm is discussed, and some limits are evaluated with simulated spectra. An experimental example is provided and compared with resolution enhancement by second derivatives. The application can be extended to other fields with dispersion-like spectra.

A simple interferometric determination for the refractive index of liquids in the infrared is presented. The transmittance spectra of the liquid sample are recorded with two cells. One cell is assembled with a window material of high refractive index, producing interference fringes from multiple reflections (Fabry-Perot etalon); the other cell yields negligible interference as it is constructed from window material with a refractive index matched to that of the sample. By absorbance subtraction it is possible to eliminate most of the absorbance features, and the resulting channel spectrum can be used for the refractive index determination without the use of iterations and Kramers-Kronig transformation. The limitations are given by a theoretical consideration for Lorentzian band shapes, and two experimental examples are presented.

An investigation of the microwave spectra of ethyl cyanide CH3CH2CN and the isotopes CH2DCH2CN, CH3CD2CN was carried out. The ground vibrational state of CH3CH2CN was reexamined under high resolution to give three centrifugal distortion constants DJ, DJKand DK. From the rotational constants of the ground vibrational state of CH3CH2CN, CH3CD2CN, CH2DCH2CN (symmetric) and CH2DCH2CN (asymmetric), CH3CH213CN and CD3CHDCN a r0-structure is derived. For the isotopes CH3CD2CN, CH2DCH2CN (symmetric) and CH2DCH2CN (asymmetric) the diagonal elements Χaa, Χbband Χccof the quadrupole tensor with respect to the principal axes of inertia were deduced from the hyperfine structure of the rotational lines. The off-diagonal element Χabfor CH3CD2CN and CH2DCH2CN (symmetric) and the principal elements Χzz, Χxxof the quadrupole coupling tensor were obtained from Χaa, Χbbof the two molecules and from the principal axis rotation angle about the c-axis produced by isotopic substitution. For the analysis of the rotational spectra in the first excited states of methyl torsion and the lowest frequency in plane bending vibration of normal ethyl cyanide a molecular model with two internal degrees of freedom is considered. From the rotational line splittings in both states the coefficients V3and V6of the Fourier expansion of the potential hindering the internal rotation of the methyl group are determined.

The measurements of the ground state rotational spectra of CH3CH2C15N and CH3CD2CN were extended to calculate the centrifugal distortion coefficients DJ, DJKand DK. The rotation-torsion-vibration interaction for these molecules including the normal species CH3CH2CN was studied in the rotational spectra of the first excited state of the methyl torsion and the CCN-in plane deformation. With respect to previous work a more detailed check of a model with five degrees of freedom comprising the overall rotation and the two lowest vibrations was possible. Potential parameters were fitted simultaneously to the splittings of the rotational transitions in the two lowest excited vibrational states of the three isotopic molecules. The coefficients V3and V6of the Fourier expansion of the hindering potential for the torsion and an interaction constant V'3cfor the torsion and the CCN-in plane deformation were determined. Using these results it was possible to reproduce the frequencies of the torsional and CCN vibrations. With less success the torsional overtones could also be calculated.

The microwave spectra of CD3CH2CN, 13CH3CH2CN, CH313CH2CN and CH3CH2C15N have been measured. In addition the spectrum of CH3CH213CN has been remeasured with greater accuracy. From these spectra and those previously reported - CH3CH2CN, CH3CD2CN, CH2DCH2CN (sym) and CH2DCH2CN (asym) - a complete rs-structure has been calculated by the equations of Kraitchman and Chutjian. r0-structure calculations were performed with different assumptions due to the symmetry of the molecule. A comparison between r0- and rs-structure was made and showed good agreement especially for the atoms of the frame.

The infrared spectrum of gaseous acetyl cyanide, CH3COCN, has been recorded from 90 - 3200 cm-1. The Raman spectrum of the liquid phase has been measured between 100 and 500 cm-1. The eighteen fundamental vibrations have been assigned, mainly on the basis of the infrared band contours, and a normal coordinate analysis has been made.

Interferometry provides us with valuable geometry information about layer thicknesses. A comparison in performance is given for different algorithms applied to infrared spectral or Fourier transformed data of empty standard liquid cells of different path lengths. Of the two procedures in the spectral domain, either only the wave numbers of the extreme values in the interference pattern are considered, or the experimental cell transmittance is fitted to a theoretical model over the whole spectral range. Fourier transformed data evaluation offers the advantage of being fast, more precise and easily interpretable. As an alternative, single-beam interferograms also offer the possibility for a straight-forward thickness analysis. The limitations of each method are discussed.

IR-spectroscopy can assist in the reliable identification of chromatographic analytes. With the direct IR-measurement of TLC and HPLC fractions, the substrate or the eluent, respectively, can render difficulties in the detection of microsamples. After isolation of the analyte, the microsampling for the different separation techniques is the same. Experiences are reported using diffuse reflectance and transmittance measurements from micropellets and enriched solutions in microcells. The performances of the microsampling techniques are compared. For often varying samples, the sample handling presented is more flexible than the different existing interfaces for the coupling of chromatography with IR-spectroscopy.

Infrared attenuated total reflection spectra of 133 whole EDTA blood samples, from patients of a general hospital population, in the range from 1500 to 750 cm-1 were used for the calibration of glucose. Reference concentration values were provided by the enzymatic glucose dehydrogenase method. The partial-least squares (PLS) algorithm was used to solve the inverse regression problem. The prediction results from, calculations using spectral and Fourier-transformed data were compared, and in the latter case, the data reduction yielded no advantage. The spectral range optimization for calibration can be carried out more flexibly in the spectral domain which is more readily interpreted by the spectroscopist.

For a solution of optically active compounds in liquid crystals, the infrared rotatory dispersion can be measured by Fourier transform spectroscopy. The results of a resolution enhancement by Fourier deconvolution and second derivative approach for the spectral features of the so-called A-Cotton effects are discussed. The experimental spectrum shown was recorded from a solution of cholesteryl oleyl carbonate in liquid crystal MBBA.

Infrared Spectroscopy can be employed for the identification of HPLC-and TLC-fractions. Different microsampling techniques with compound isolation were considered: transmittance measurements using micropellets and microcells with enriched solutions; other experiments were done with accessories for diffuse reflectance. The performance of the techniques is limited by the isolation step. The identification limits for ideal samples (about 50 ng) can be one order of magnitude lower than for Chromatographic fractions due to sample handling problems.

50 patients suffering from acute or chronic urticaria have been subjected to a xylose-test. In these patients resorption disturbances of the small intestine with regard to carbohydrates could be clearly demonstrated in terms of statistics. Particularly patients suffering from chronic urticaria were affected. However, none of the aforementioned disturbances were to be observed both in urticaria facticia and urticaria-type exanthems caused by drugs. So far only in a small group of patients suffering from pruritus and prurigo, respectively an increase in the resorption of carbohydrates could be suspected.

Investigations were carried out on the basis of the hypothesis that Cr6+ is reduced to Cr3+ on penetrating the skin. Therefore, skin cuts, taken from positive and negative Cr6+ patch skin tests, were treated with fluorescensed Cr3+ antisera. The positive patch skin test showed deposits of chromium ions in the corium. In the negative Cr6+ test, however, chromium ions were found in the stratum corneum and in the upper stratum granulosum only. Negative Cr3+ control-tests delivered deposits in the stratum granulosum and in the upper stratum spinosum. Differences in resorption between sensitized and nonsensitized skin can be assumed from these results.

Investigations of skin cuts taken from positive potassium bichromate patch skin tests were carried out by means of the indirect fluorescence technique according to Weller and Coons. Punctiform indications of fluorescence were to be found due to ?-globulin-complexes. On this method the fluorescence is considered to be specifical, it is, however, pointed out that the antibody character of the ?-globulin-complexes located at these spots cannot be proved. The controltests carried out yielded negative results. The investigations are continued.

Chloro-dinitrobenzene eczema of guinea-pigs were treated with Dimethylsulfoxide (DMSO). The following results were obtained:1.The guinea-pigs were treated with a 1% solution of chloro-dinitro-benzene in aceton with DMSO added, and a pure 1% solution of chloro-dinitro-benzene in aceton. The sensibilisation was faster by application of the solution with added DMSO.2.The DNCB-DMSO treated guinea-pigs showed a higher degree of sensibilisation in comparison with the group which was treated without DMSO.3.It is possible to reduce the concentration of the chloro-dinitrobenzene solution if DMSO is added. Guinea-pigs which were sensibilisised with chlorodinitrobenzene dissolved in acetone only, showed an allergic reaction when they were treated with that less concentrated solution.

Die drei verschiedenen Prinzipien der Anwendung fluorochrommarkierter Antikörper werden herausgestellt. Über die Herstellung von fluorochromiertem Anti-Gamma-Globulin zum indirekten Antikörpernachweis nach Welleru. Coonswird ausführlich berichtet. Besonderer Wert wird auf die Darstellung der Tiersensibilisierung und der Fluorochromierung des Antiserums gelegt. Einige methodische Varianten werden dabei einer kurzen Kritik unterzogen. Über die bei verschiedenen Dermatosen mit diesen fluorochromierten Antiseren gewonnenen Erkenntnisse wird in weiteren Mitteilungen berichtet.