Of spectrograde solvents

Table 7.9 Electronic Absorption Bands for Representative Chromophores Table 7.10 Ultraviolet Cutoffs of Spectrograde Solvents Table 7.11 Absorption Wavelength of Dienes Table 7.12 Absorption Wavelength of Enones and Dienones Table 7.13 Solvent Correction for Ultraviolet-Visible Spectroscopy Table 7.14 Primary Bands of Substituted Benzene and Heteroaromatics Table 7.15 Wavelength Calculation of the Principal Band of Substituted Benzene Derivatives...

TABLE 7.10 Ultraviolet Cutoffs of Spectrograde Solvents Absorbance of 1.00 in a 10.0 mm cell V5. distilled water. 

The cut-off point in the ultraviolet region is the wavelength at which the absorbance approaches 1.0 using a 1-cm cell path with water as the reference. Solvents should not be used for measurements below the cut-off point, even though a compensating reference cell is employed. The cut-off points are very dependent on the purity of the solvent used. Most of the solvents listed above are available in highly purified spectrograde quality. 

Oresyl violet (Exiton) was used as received. Spectrograde acetonitrile, methanol and ethanol were used without further purification. Two or three samples of each solvent with different dye concentration in the order of 10" M were used for the measurements. No concentration effect on the time correlation function was observed. 

Solvent. The following solvents that are transparent in the UV—Vis region are usually used water, MeOH, EtOH, acetonitrile, cyclohexane, and hexane. When a sample is weakly soluble in EtOH, a mixed solvent is used the sample is dissolved in a small amount of 1,4-dioxane and then diluted with EtOH. Spectrograde solvents should be used. 

Acetonitrile (Eastman Spectrograde) was used without further purification, since fractional distillation had little effect on the spectrum of the solvent or upon the rate of pyrimidine photolysis in die neat solvent. 

TaUe 5. Detennination of cesium in spectrograde solvents, body fluids, and environmental samples by field desorption mass spectrometry using an external standard ... 

Polymer Characterization. Proton NMR spectra at 300 MHz were obtained from a Varian HR-300 NMR spectrometer. Deutero-benzene and spectrograde carbon tetrachloride were used as solvents. The concentration of the polymer solutions was about 1-5%, Carbon-13 NMR spectra were obtained from a Varian CFT-20 NMR spectrometer, using deuterochloroform as the solvent for the polymers. The concentration of the solutions was about 5%. Chemical shifts in both proton and carbon-13 spectra were measured in ppm with respect to reference tetramethylsilane (TMS). All spectra were recorded at ambient temperature. 

All solvents used are either spectrograde or analytical grade. The analytical grade solvents are further purified by fractional distillation whenever blank determinations suggest the presence of impurities detectable by flame ionization GC. 

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