Internal standardization method: 

in these techniques, known amounts of sample and standard are mixed and chromatographed. The peak areas for sample elements and for standard are measured and ratios of both peak areas are determined. Either area ratios are plotted against weight ratios to acquire a graph or area ratios for unknown are compared directly along with those for the known amounts. Therefore, accurately known quantity of the internal standard is added to the unknown sample and this combination is chromatographed and area ratios are measured.

The needs for a appropriate internal standard are summarized as follows:

• The standard must be a compound that is well separated from all elements of the mixture being analyzed.
• The standard must not react along with any component of the sample, nor should it influence the physical properties of the other elements, e.g. volatility.
• It could yield a symmetrical chromatographic peak.
• It must be chemically same to the unknown.
• It should have concentration comparable to the elements of interest.