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4.- An industrial analyst wishes to compare the internal standard method with the standard addition method for the analysis of K. He previously decided to use Li as a reference element in the intemal standard method. From the data specified below, calculate the concentrations of K by both methods. a) Internal standard based on the data presented in the following table: b) Standard addition: Standard samples containing 0,1,2,5,10,20 and 50ppm of K are prepared. An aliquot of 10mL of each of the previous solutions is mixed with 10mL of the problem and the following intensities: 18.0, 19.5, 21.0.25.5, 33.0, 48.0, 93.0. Note: report concentration in parts per million