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. Author manuscript; available in PMC: 2017 Feb 1.
Published in final edited form as: J Pharm Sci. 2016 Jan 29;105(2):664–672. doi: 10.1002/jps.24539

Figure 2.

Figure 2

13C-NMR spectra of pyruvic acid (1, oxo form and its hydrate) at different pH values, 5.4, 2.3 and 0.9 (top to bottom on the left).Observed chemical shifts (δobs) of the signals arising from the carbon in position 1 associated with the oxo and hydrated forms of 1 plotted against pH (right).The two continuous lines with a sigmoidal shape are described by Eq. 14, fitting δobs values at different pH values.