How much medicine is in my medicine?

NMR spectroscopy is typically introduced to undergraduate students in the organic chemistry curriculum with an emphasis on structural elucidation. Although this approach is great for qualitative analysis, students are not introduced to the quantitative aspect of NMR, termed quantitative NMR (qNMR), an equally important and powerful aspect of NMR spectroscopy, especially for industrial applications. In this blog post we show a simple experiment that teaches students how common over the counter (OTC) medications can be qualified and quantified for their different active pharmaceutical ingredients (API) using qNMR spectroscopy. This experiment can easily be incorporated into any undergraduate laboratory and demonstrates the applicability of NMR in different applications, especially in the pharmaceutical industry. For a more detailed experimental procedure on how to qualify and quantify simple OTC medication, click here .

An OTC medication containing acetaminophen was acquired from the local drug store. One capsule was then crushed up and a small amount was co-dissolved into DMSO-d₆ with maleic acid (the internal calibrant for qNMR) and analyzed with the Nanalysis 60 MHz instrument. Shown below (Figure 1) is a graphic which highlights the different chemical species present in our medication as well as their respective ¹H NMR signals. The NMR spectra are stacked on top of one another to aid in visualizing and identifying which signals are representative of each chemical species. Figure 2 showcases the different regions that were integrated to determine the relative amounts of each API.

Figure 1. Stacked plot of ¹H (60.7 MHz) NMR spectra representing OTC medication with maleic acid internal calibrant (1), acetaminophen (2), caffeine (3), and maleic acid (4).

Figure 2. ¹H (60.7 MHz) NMR spectrum of an OTC medication and maleic acid dissolved in DMSO-d₆. Signals of interest for acetaminophen, maleic acid, and caffeine are annotated, peak picked, and integrated.

Table 1. Comparison between masses obtained via ¹H NMR spectroscopy and manufacturer’s label.

After identifying the different components in the medication, the APIs can easily be quantified by qNMR (click here to learn more about qNMR). Table 1 displays the relative amounts of each API and compares the result we obtained to the labels present on the medication. As we can see, the values obtained using the Nanalysis 60 MHz instrument correlates well with the pharmaceutical labels. This experiment was simple to perform and can easily be incorporated into undergraduate laboratories to emphasize the importance of NMR spectroscopy as both a qualitative and quantitative analytical technique. If you would like to know more about experiments with NMR spectroscopy or are interested in how benchtop NMR could help you, please do not hesitate to contact us.