2. Procedure: 1.Measure blank. 2.Measure standard. 3.Measure unknown. 4.Subtract blank from standard and from unknown. 5.Calculate concentration of unknown If you have several (N) standards, do it several (N) times

3. Use your sample as a new “blank”: Add a known amount to your sample XX + standard IxIx I x+standard Increase in intensity: because of this addition I x+standard – I x

4. Procedure: 1.Measure unknown. 2.Add a known amount to the unknown and measure this sample. 3. Subtract (2) from (1). 4. Calculate concentration of unknown If you have several (N) standard additions, do it several (N) times

5. Internal Standard Why and when? All intensities vary from sample to sample Sample 1 x s Sample 2 0.6x 0.6s Sample 3 1.2x 1.2s No reproducibility! Let us divide intensity in the first column by the intensity in the second: Sample 1 x s x/s Sample 2 0.6x 0.6s x/s Sample 3 1.2x 1.2s x/s Now they are the same!

6. Restriction: you need to measure 2 values simultaneously You may prefer to have the same amount of internal standard in all your samples Procedure: 1. Add equal amounts of the internal standard to all your standards and analytes. 2. Measure intensities of your target compound (atom) and your internal standard in your solutions. 3. For each pair of measurements, divide the intensity coming from your target compound by the intensity of the internal standard. 4. Process these new “normalized” intensities like you did before.