Explain the Calibration Curve method & Standard addition method.

(1) Calibration Curve Method:

We take some known concentration of the given solution and find the intensity of the emitted light.

Conc.	O.D.
5 ppm	50
10 ppm	100
15 ppm	150
20 ppm	200
25 ppm	250
30 ppm	300
Unknown	125

A graph of intensity measured Vs Conc is plotted. Now the intensity of the test solution is measured.

Take this value on the intensity axis and draw the line parallel to the X-axis where it cuts the standard curve, from there draw the perpendicular to the conc axis which will give the concentration.

(2) Standard Addition Method:

In this method the intensity of the light of the test solution is measured with reference to the blank. Now known increasing amount of the element to be determined are then added to a number of the test solutions and the solutions are diluted to the same volume in each case.

Conc.	O.D.
x + 0 ppm	150
x + 5 ppm	200
x + 10 ppm	250
x + 15 ppm	300
x + 20 ppm	350
x + 25 ppm	400
x + 30 ppm	450

Intensity of the light of each solution is determined. A graph of readings Vs slandered conc added is plotted the graph will be straight line this line is extrapolated on conc axis which gives the concentration.