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The Quantitative Analysis of an Analgesic Tablet: An NMR Experiment for the Instrumental Analysis Course

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Thomas A. Schmedake and Lawrence E. Welch

Knox College, Galesburg, IL 61401

J. Chem. Educ., 1996, 73 (11), p 1045

DOI: 10.1021/ed073p1045

Publication Date (Web): November 1, 1996

Section:

History, Education, and Documentation

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.

Keywords (Audience):

Second-Year Undergraduate

Keywords (Domain):

Analytical Chemistry

Keywords (Pedagogy):

Hands-On Learning / Manipulatives

Keywords (Subject):

Quantitative Analysis

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This article has been cited by 2 ACS Journal articles (2 most recent appear below).

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