Ultraviolet-visible spectroscopy alcohols

A solvent for ultraviolet/visible spectroscopy must be transparent in the region of the spectrum where the solute absorbs and should dissolve a sufficient quantity of the sample to give a well-defined analyte spectrum. In addition, we must consider possible interactions of the solvent with the absorbing species. For example, polar solvents, such as water, alcohols, esters, and ketones, tend to obliterate vibration spectra and should thus be avoided to preserve spectral detail. Nonpolar solvents, such as cyclohexane, often provide spectra that more closely approach that of a gas (compare, for example, the three spectra in Figure 24-14). In addition, the polarity of the solvent often influences the position of absorption maxima. For qualitative analysis, it is therefore important to compare analyte spectra with spectra of known compounds measured in the same solvent. 

Following ultraviolet-visible spectrophotometry and infrared (IR) spectroscopy, gas chromatography (GC) was one of the first instrumental techniques to help in solving forensic science problems. The early very successful applications included the determination of blood alcohol by direct injection of blood or serum, and the detection and identification of petroleum products in debris from arson cases in 1958/59. The breakthrough of GC in these areas and in drug analysis was an event of the 1960s and the 1970s. 

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