Page 22 - Instrumental Analysis - Pharm D Clinical- 07-PA403

UV-visible Spectrophotometry

1- Source of Light

• It must be of sufficient energy.
• It must cover the desired spectral range.
• It should provide an output that is both intense and

stable during measurement time.
• In visible region, we use tungsten lamp (380-800 nm).
• In UV region, we use deuterium lamp (D2) or hydrogen

lamp (120-380 nm).

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2- Wavelength Selector
(monochromator or dispersing system)

• It converts polychromatic light to monochromatic light.
• In the isolation of a monochromatic light from the spectrum, we need

to mention 2 values: the nominal λ (average λ) and the bandwidth.
• For example, if the radiation comprises λ values in the range 520-

530 nm, thus nominal λ = 525 nm and bandwidth = 10 nm.
• Types of monochromators:

I- Filters
II- Prisms
III- Gratings

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