Monitoring of environmental quality often requires determination of substances occurring in very small quantities in presence of plenty of unwanted materials which interfere in the process of analyses. The classical methods of Analytical Chemistry which include gravimetry, titrimetry or volumetry etc. are often inadequate for the purpose.
These methods fail miserably when heavy metals, toxic ions and pesticides present in trace quantities (in the concentration range of part per million or so) have to be investigated. In addition to these methods which essentially utilize the chemical properties of a substance for analyses, a number of methods are available which make use of physical properties as well.
In order to characterise and measure these properties accurately sophisticated instruments are required and hence these methods are also referred to as instrumental methods of chemical analyses. Today, these methods have become the back-bone of analytical chemistry. They very often measure accurately concentrations in the range of parts per million or even parts per billion, and are convenient and cheap as well.