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  Home > JCE Print > Journal of Chemical Education > Issues > 1996  > November  >
In the Laboratory
The Quantitative Analysis of an Analgesic Tablet: An NMR Experiment for the Instrumental Analysis Course
Thomas A. Schmedake and Lawrence E. Welch
Knox College, Galesburg, IL 61401
Cover
November 1996
Vol. 73 No. 11
p. 1045
Abstract
A quantitative analysis experiment is outlined that uses 13C NMR. Initial work utilizes a known compound (acenapthene) to assess the type of NMR experiment necessary to achieve a proportional response from all of the carbons in the compound. Both gated decoupling and inverse gated decoupling routines with a variety of delay times are inspected, in addition to investigation of paramagnetic additives in conjunction with inverse gated decoupling. Once the experiments with the known compound have illuminated the merits of the differing strategies for obtaining a proportional carbon response, a quantitative assessment of an unknown analgesic tablet is undertaken. The amounts of the two major components of the tablet, acetaminophen and aspirin, are determined following addition of an internal standard to the mixture. The carbon resonances emanating from each compound can be identified using spectra of the pure analgesic components and internal standard. Knowing the concentration of the internal standard and assuming a proportional response to all carbons in the sample allows calculation of the amount of both analytes in the analgesic tablets. Data from an initial laboratory trial is presented that illustrates the accuracy of the procedure.
More Information
*  Citation
 Schmedake, Thomas A.; Welch, Lawrence E. J. Chem. Educ. 1996 73 1045.
*  Keywords
 Analytical Chemistry
*  History
 Created:
Last Updated:		 August 5, 1999
February 21, 2006
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