Interpretation:
An internal standard and its uses needs to be explained.
Concept introduction:
Use of an internal standard before actual sample analysis is an established method in analytical tests and is one important step towards eliminating/reducing the sources of errors and ensuring the accuracy and precision of the results.
Answer to Problem 10.1QAP
An internal standard is a chemical substance, added to the sample, blank or calibration standards to identify and account for uncontrollable variables. The uncontrollable variables are expected to affect the internal standard and the analyte to a similar extent.
Explanation of Solution
Before actual analytical analysis of a substance, a blank and/or a calibration standard is run. This consists of a chemical substance of known composition and purity. It is added in a known quantity. This responds to the analytical and measurement processes as will the actual substance sample.
This is used to draw a calibration curve with the signals of internal standard on Y axis.
The accuracy of the results is increased as the instrument noise gets eliminated. This is because the signal to noise ratio is the same for the internal standard as for the substance under analysis.
Running the internal standards prior to running the analyte, improves the accuracy of the results. The internal standard, however, is to be properly selected.
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Chapter 10 Solutions
Principles of Instrumental Analysis, 6th Edition
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