UV-Visible and Infrared Spectroscopic Methods in Environmental Analysis - Fundamentals of Environmental Sampling and Analysis - page 207

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Light source Monochromator Sample cell Detector Readout

Figure 8.14 Schematic diagram of a typical single beam UV-visible light spectrometer

Monochromator (wavelength selector) : It consists of an entrance slit
that narrows the bandwidth of radiation, a collimator that makes the
radiation parallel, a grating or prism that disperses unwanted radiation,
and an exit slit that isolates the desired wavelength of radiation from the
grating. Glass prisms and lens can be used in the visible range, but quartz
or fused silica materials must be used in the UV region.
Cuvette (sample cell) : It is used to hold sample. Quartz cuvettes are
transparent to UV and visible radiation and, therefore, are more com-
monly used for UV-VIS spectroscopy.
Detector (transducer) : It changes the radiation transmitted from the
UV-VIS spectrometer into a current or voltage for the readout device
to use. Solid-state photodiodes, photoemissive tubes, and photomulti-
plier tubers (PMT) are commonly used as single element detectors,
whereas solid-state array detectors are used as multielement detectors.
The operational principles are complicated (Albert Einstein received the
Nobel Prize in 1921 for his discovery of the photoelectric effect, not for
his well-known relativity theory), but fortunately, practical users can
consider it as a black box and they rarely need to know the theory behind
these detectors in examining the electronic and mechanical details of
these optical instruments.

Absorbance readout

Mode indicators

Mode select button

Wavelength readout

Decrease

Increase

550 0.000

Spectronic 20D

Wavelength control

Sample holder

On/Off switch - Zero control

100% Transmittance control

Figure 8.15 A simple visible wavelength light spectrometer (http://www.chemistry.nmsu.edu/

Instrumentation/Spectronic-20.html)