Raman spectrometer measures multipoint data of intensity versus
frequency known as "spectra". The bands in the spectra
are related to molecular structure, and each molecule has a very
specific overall pattern that can be matched to spectra of known
standards. The InPhotote offers a wide spectral range (to differentiate
many types of molecules), and high resolution (to separate individual
bands resulting in clearer spectra).
are spectra of four narcotics. Note how each spectrum is visibly
different. The two forms of cocaine (at bottom) are very similar,
but show distinct differences between 800 - 1300 cm-1.
These differences would be difficult to see on a spectrometer with
lower spectral resolution.
here are spectra of three clear, colorless liquids measured through
glass containers. The top is a mixture of two organic liquids, one
being acetonitrile. Acetonitrile contains a cyanide linkage that shows
up near 2250 cm-1. This band is very specific for cyanide
and can be easily used to identify other cyanide-containing unknowns.
The lower spectrum shows a mixture of chlorinated compounds; the carbon-chlorine
linkages give rise to bands at lower frequencies (below 500 cm-1).
The middle spectrum shows a pure hydrocarbon solvent, whose main bands
of the carbon-carbon backbone show up in the middle of the spectral
"over-the-counter" drugs were measured through the blister
packaging commonly used for such medications. Although the active
ingredient is usually too dilute to be identified by Raman spectroscopy,
the excipients and tablet coatings can be used to screen for counterfeit
drugs. The antihistamine tablet shows the strong bands of TiO2,
a common filler. The decongestant gelcap shows components from the
gel and gelcap. Both spectra were measured without having to open
the packaging material and without destroying the tablets.
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