Preliminary Regions to Examine

It is usually advisable to tackle the bands at the higher-frequency end of the spectrum, the most intense bands being looked at first and associated bands. 

Small traces of moisture in an organic solvent, such as carbon tetrachloride or hydrocarbon solvents, give rise to bands due to O-H vibrations in this region. A broad, weak band may also be observed near 1650 cm (6.06 gm). Such bands are particularly noticeable using thick sample cells of long pathlength. 

Occluded water in some fused silica windows gives rise to a sharp band. 

Solid samples containing water have a band in this region and also a band near 1650 cm (6.06 gm). 

A band due to atmospheric carbon dioxide may be observed in older or poorly-adjusted instruments, for example, if the sample and reference beams of a double-beam spectrometer are not properly balanced. Also, a band near 665 cm (15.04 gm) is observed. 

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