Regions of spectrum

Sample detection in polymer HPLC is a large problem. Only few polymers bear chromophores that allow direct application of photometers, typical for HPLC of many low-molar-mass substances. The use of detectors that operate in the infrared region of spectrum is complicated by the absorptivity of eluents. Still, there is observed some revival in this area, especially in the SEC of polyolefins. 

Figure 5. Infrared spectrum at room temperature of VSil545 after evacuation at 500 C (a) and after contact at room temperature with 50 torr of propane (b). Reported in the inset is the expansion in the 1300-1550 cm region of spectrum b after subtraction of spectrum a. The background spectrum due to gaseous species has been subtracted.

FiG.ll. NMR spectra of H2O solutions of Cua domains from (A) Paracoccus denitrificans, 800 MHz, pH 5.6, and (B) Thermus thermophilus, 600 MHz, pH 4.5. Asterisks denote exchangeable signals. The 100- to 500-ppm region of spectrum (A) is recorded as a H NMR spectrum. Signals a and c are not visible in the H spectrum. NOE connectivities are also shown. Adapted with permission from Luchinat et al. (1997 Copyright 1997 American Chemical Society). 

Other characteristics of conjugated molecules can also be indicated the shift of the UV absorption maximum of butadiene and other polyenes to the longwave region of spectrum as compared to ethylene, the lowering of ionization potentials, and so on. In short,. there is much evidence pointing to the fact that the properties of conjugated systems are determined by the interaction of multiple bonds. 

Figure 7. Two-color fluorescence spectra of the I-naphthylmethyi and 2-naphthyl-methyl radicals. Spectra were produced by excitation of the sample with a 25-ps, 266-nm laser pulse followed by a 25-ps, 355-nm pulse delayed by 60 ps. Key to (halo-methyljnaphthalenes a, I-(chIoromethyI)naphthaIene b, 2-(chloromethyl)naphthalene c, I-(bromomethyI)naphthalene and d, 2-(bromomethyl)naphthalene. Note the fluorescence in the blue region of Spectrum c is due to impurities that contaminated the sample of l-(bromomethyl)naphthalene (28).

X in GaAsj. P. Substrate A/nm Observed colour or region of spectrum... 

Th Mai(PET) No interfering peaks in this region of spectmm Mai (PET) No interfering peaks in this region of spectrum... 

FIGURE 40.6 Electrospray ionization spectrum of MC-LR obtained using a quadrupole ion-trap mass spectrometer, (a) Source CID-MS spectrum (b) Expanded MS region of spectrum A m/z = 130-140 [125]. 

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