Chemistry Reference
In-Depth Information
7
Analytical spectroscopy
Analytical spectroscopy is the science of determining how much of a
substance is present in a sample by accurately measuring how much light is
absorbed or emitted by atoms or molecules within it. Different types of
spectroscopy are available, depending on the type or wavelength of electro-
magnetic radiation absorbed or emitted by the atom or molecule. A detailed
review of all types of modern instrumental analysis is beyond the scope of
this topic, but the use of
spectroscopy in the analysis of
drugs and
medicines is very important and will be considered.
Light is a form of electromagnetic radiation, so called because it
consists of an electric component and a magnetic component, which oscil-
late in mutually perpendicular directions and perpendicular to the direction
of travel of the radiation through space (see Figure 7.1).
Electric component
Magnetic component
Direction of travel of light
Figure 7.1
A diagrammatic representation of electromagnetic radiation.
The complete spectrum of electromagnetic radiation is shown in
Figure 7.2 and ranges from low-energy radio and television waves through
to very high-energy gamma rays. The tiny part of the electromagnetic spec-
trum that human eyes can detect (approximately 400-700 nm) is called the
visible spectrum, and spectroscopy carried out at these wavelengths is
termed visible spectroscopy or 'colorimetry'.
