Spectra of mixtures

An investigation of the infra-red spectra of mixtures of nitric acid and acetic anhydride supports these conclusions. The concentration of nitronium ions, measured by the absorption band at 2380 cm, was... 

Figure 6.23 Fluorine-19 nmr spectra of mixtures of boron halides showing the presence of mixed fiuorohalogeno-boranes.

Lee, J., Wang, Y., and Gibson, B. G. (1990). Recovery of components of fluorescence spectra of mixtures by intensity- and anisotropy decay-associated analysis the bacterial luciferase intermediates. Anal. Biochem. 185 220-229. 

Fig. 34.2, UV-visible spectra of mixtures of fluoranthene and chrysene (see Fig. 34.3 for the pure spectra).

Spectra at p (=20) wavelengths. Because of the Lambert-Beer law, all measured spectra are linear combinations of the two pure spectra. Together they form a 15x20 data matrix. For example the UV-visible spectra of mixtures of two polycyclic aromatic hydrocarbons (PAH) given in Fig. 34.2 are linear combinations of the pure spectra shown in Fig. 34.3. These mixture spectra define a data matrix X, which can be written as the product of a 15x2 concentration matrix C with the 2x20 matrix of the pure spectra ... 

The study of molecular diffusion in solution by NMR methods offers insights into a range of physical molecular properties. Different mobility rates or diffusion coefficients may also be the basis for the separation of the spectra of mixtures of small molecules in solution, this procedure being referred to as diffusion-ordered spectroscopy (DOSY) [271] (Figure 5.11). In this 2D experiment, the acquired FID is transformed with respect to 2 (the acquisition time). 

The mass spectra of mixtures are often too complex to be interpreted unambiguously, thus favouring the separation of the components of mixtures before examination by mass spectrometry. Nevertheless, direct polymer/additive mixture analysis has been reported [22,23], which is greatly aided by tandem MS. Coupling of mass spectrometry and a flowing liquid stream involves vaporisation and solvent stripping before introduction of the solute into an ion source for gas-phase ionisation (Section 1.33.2). Widespread LC-MS interfaces are thermospray (TSP), continuous-flow fast atom bombardment (CF-FAB), electrospray (ESP), etc. Also, supercritical fluids have been linked to mass spectrometry (SFE-MS, SFC-MS). A mass spectrometer may have more than one inlet (total inlet systems). 

ESI mass spectra of mixtures are difficult to interpret, because each component produces ions with many different charge states. The most direct and reliable method to solve this problem is to use high-resolution MS and calculate the charge states by measuring the spacing of the isotope peaks. ESI mass spectrometry of (polymeric) mixtures with broad molecular weight distribution benefits from a prior separation that reduces the polydispersity of the analyte. 

The use of computer algorithms to deconvolute MALDI or ESI spectra of mixtures of microorganisms obtained under uncontrolled conditions is less likely to be successful, as discussed above. 

Because unidimensional NMR spectra of denatured proteins lack resonance dispersion and resemble spectra of mixtures of free amino acids, it was assumed that the denatured state behaves as a random coil (McDonald and Phillips, 1969). Calculations (Brant et al., 1967 Zimm and Bragg, 1959) and spectroscopic measurements on... 

IR Spectroscopy. Samples of the hexane layer (8-4, 4-4, 2-4, 1-4), after evaporation of the solvent, gave IR spectra of mixtures of TBTC1 and TBTA. The amount of TBTA depended on the concentration of sodium chloride solution and its volume, as evidenced by the intensity of the broad peak at 1650 cm-1. 

Fig. 9. Experimental and simulated room-temperature X-band CW-EPR spectra of mixtures of oxo-Cr(V)/36.

To construct a CIS model, the pure spectra for all analytes are obtained to fonn the S matrix. Two CLS methods are discussed, direct (Section 5.2.1), where the spectra are measured directly, and indirect (Section 5.2.2), where the pure spectra are computed from spectra of mixtures with known composition. 

The calculation of spectra of pure compounds from spectra of mixtures. 

H NMR spectra of the trimeric isopropoxides M(OCHMe2)4 (M = Zr or Hf) indicate rapid exchange of terminal and bridging isopropoxide groups 1HNMR spectra of mixtures of... 

Spectrum.5—The arc and spark spectra of tellurium have been investigated, the arc being produced in an atmosphere of carbon dioxide between tellurium electrodes or between carbon electrodes one of which carried pieces of tellurium in a small cavity. Fifteen distinctive lines between 3175 and 2081 A 6 and forty of wave-length less than 2080 A 7 have been measured. The most prominent lines are 2142-75, 2259-02, 2383-24, 2385-76, 2769-65 and 3175-13 A. The lines at 2769-65 and 3175-13 have been shown to be distinct from those of antimony (2769-94) and tin (3175-04) by photographing the spectra of mixtures of these elements with tellurium, when in each case the two separate lines were obtained.8... 

Fig. 85. Two-dimensional, 3C spin diffusion spectra of mixtures of adamantane and 2,2,3,3-tetramethylbutane at 75.4 MHz (424) (a) Mixture of powders (b) mixture by melt. Note the absence of cross-peaks between signals belonging to different species in the heterogeneous sample in (a).

Fig. 9. Fluorescence emission spectra of mixtures of nuclease-T-(49,50-149) with nuclease-T-(6-48) or synthetic peptides upon excitation at 295 nm. Samples containing 2 X 10 s M nuclease-T-(49,50-149) and 4 X 10 M nuclease-T-(6-48) or synthetic peptide were in 0.05 M tris, pH 8, with 0.01 M CaCh and 0.0001 M pdTp. The spectrum for nuclease-T-(49,50-149) alone was corrected for the small measured emission exhibited by the buffer solution containing pdTp and Ca2+. The spectra for mixtures of synthetic peptide or nuclease-T-(6-48) with nuclease-T-(49,50-149) were corrected for the measured emission exhibited by the appropriate synthetic peptide tor nuclease-T-(6-48) 1 alone in buffer containing pdTp and Ca t. (0) Nuclcase-T-(6-48), (O) synthetic (6-47), (A) synthetic (9-47), (A) synthetic (18—47), ( ) synthetic (33-47), and ( ) nuclease-T-(49, 50-149) alone. Taken from Ontjes and Anfinsen (87).

Grondey et al. [1986] used this method to analyze the INS spectra of mixtures (CH. Kr, in which the available configurations include not only various spin-rotational states of methane molecules, but also the states where these molecules are partially substituted by krypton atoms. 

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