UV-Vis Spectrophotometer 

A UV-Vis spectrophotometer is a widely used instrument to take absorbance

measurements. There are many commercial manufacturers of these instruments,

but they all have the same basic working components: a light source, a way to

select the wavelength of light, a sample holder, and a way to detect the amount

of light.

The light source, wavelength selector, and light detector are all typically

controlled by the instrument’s computer interface, while the specifics will depend

on the instrument being used. The typical sample holder for UV-Vis absorption

spectroscopy experiments is a cuvette. A cuvette is small container - typically

made of quartz, glass, or plastic - with a known width (commonly 1 cm). If

measurements are being done in the visible region, then glass or plastic will work

well, but quartz must be used if measurements are performed in the ultraviolet

region of the spectrum. Proper care and use of a cuvette are two of the most

important steps for achieving accurate and reliable results in UV-Vis

spectroscopy.

Use of a Cuvette

The entire technique relies upon how much light makes it through the sample.

The light passes through the walls of the cuvette and the sample before being

detected by the instrument. This makes the walls of the cuvette a critical part of

the measurement. Think about trying to look through glasses that have a

fingerprint on them. The amount of light that reaches your eye changes because

of the presence of the fingerprint! When working with the cuvette our goal is to

minimize the impact of the cuvette walls on the measurement and to make the

impact from the walls consistent for each measurement. To accomplish this, use

the following guidelines:

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Figure 8.5: 4.4: UV-Visible Spectroscopy is shared under a CC BY 4.0 license and was authored,

remixed, and/or curated by Pavan M. V. Raja & Andrew R. Barron (OpenStax CNX).