Page 9 - Instrumental Analysis - Pharm D Clinical- 07-PA403

UV-visible Spectrophotometry

• We focus here on absorption spectroscopy in the UV/visible region of
the EMR spectrum.

• Ultraviolet (UV) region = 200 – 400 nm. Visible region = 400 – 800 nm.
• A beam of light carrying radiation of several wavelengths is said to be

polychromatic.
• A beam of light carrying only one discrete wavelength is said to be

monochromatic.

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Types of Electronic Transitions

n
n
Electrons in a molecule can be classified into:
• Covalent single-bond electrons ( “sigma” electrons).
• Covalent double or triple bonds electrons ( “pi” electrons).
• Non-bonding pairs of electrons (n electrons). These can be
found on elements like O , N and halogens.

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