Comment on “Purity Analysis of the Pharmaceuticals Naproxen and

Apr 16, 2015 - Ironically, as published, this paper offers an excellent teaching opportunity calling for close reading of the text and critical analys...
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Comment on “Purity Analysis of the Pharmaceuticals Naproxen and Propranolol: A Guided-Inquiry Laboratory Experiment in the Analytical Chemistry Laboratory” Alan M. Rosan* Chemistry Department, Drew University, Madison, New Jersey 07940, United States ABSTRACT: This letter to the editor comments on the paper, “Purity Analysis of the Pharmaceuticals Naproxen and Propranolol: A Guided-Inquiry Laboratory Experiment in the Analytical Chemistry Laboratory”. KEYWORDS: Upper-Division Undergraduate, Analytical Chemistry, Inquiry-Based/Discovery Learning, Spectroscopy

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read with interest the report by Dr. Sayo Fakayode in the January 2015 issue of this Journal.1 This informative paper introduces a guided-inquiry laboratory investigation comprising a thorough purity analysis by FT−IR, GC, GC−MS, and HPLC of the important pharmaceuticals naproxen and propranolol. However, the statement that naproxen chloride is an oftprescribed anti-inflammatory and therefore the analyte, as mentioned many times in the article and shown in Figure 1, is in error. The hydrolytic instability of naproxen chloride precludes it from being the structure of the active drug. As strongly suggested by the preparation of samples in 80:20 ethyl acetate:methanol, it is naproxen methyl ester that is being analyzed. This assignment is consistent with the IR spectrum shown in Figure 2B (ester carbonyl at 1750 cm−1) and the mass spectrum shown in Figure 4C (parent ion m/z 244 not m/z 248) that clearly does not display the chlorine isotope signature expected for the acid chloride. The base peak seen at m/z 185, incorrectly attributed to [M-COCl], is actually [M-CO2CH3]. Naproxen sodium, available in Aleve and other over-thecounter products, is the likely source of the analyte discussed here. Ironically, as published, this paper offers an excellent teaching opportunity calling for close reading of the text and critical analysis of the data presented.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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REFERENCES

(1) Fakayode, S. Purity Analysis of the Pharmaceuticals Naproxen and Propranolol: A Guided-Inquiry Laboratory Experiment in the Analytical Chemistry Laboratory. J. Chem. Educ. 2015, 92 (1), 157− 162.

Published: April 16, 2015 © 2015 American Chemical Society and Division of Chemical Education, Inc.

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DOI: 10.1021/acs.jchemed.5b00133 J. Chem. Educ. 2015, 92, 784−784