Internal Standard Method:

Within this method, a constant amount of another metal that is not present in the sample is added to both the unknown sample and a series of standard solutions of the components be determined. This is known as internal standard, for example, lithium is added within the determination of sodium metal. Because both the element and the internal standard are in the similar solution, the emission readings at the wavelengths of both an internal standard and the element to be enclosed are concurrently determined. The intensity ratio for the two parts is then plotted against concentration of the standard solution. From the observed ratio for the sample, the concentration of the element in it could be determined. Let us take an instance to understand it.