Question

Explain the principle of quantification via standard addition. Give (in general terms, without going into specific details) an example of an analytical problem/error that can be corrected for using standard addition, and explain how the internal standard helps to correct that problem/error. Then illustrate graphically how quantification of an unknown sample is done in chromatographic analyses using standard addition 2 (as opposed to external calibration)

Answer 1

Solution:

The sample analysis using chromatography intense signals are affected by sample matrix, temperature and other parameters in order to overcome (or) in rectification a standard is added directly to the sample aliquot for calibration to achieve precise signal yielding values accurately. In order to succeed in standard addition the following two points have to be fulfilled,

1. The graph have to be linear after calibration

2. The analyte must have to pass through origin in the calibrated curve

by this standard addition calibration the signal is optimized to a value of 1.3 to 3 times higher and the expression used in computation is expressed below for each addition of standards,

where, C_x is analyte concentration without standard

C_x + C_s is analyte with standard addition

The sample graph of copper ion detemination by standard adiition is expressed below for quick grasping of the concept of quantification by standard addition.