Neotame polymorphic forms

Fig. 2 Plot of the results of a multiple-contact time experiment of neotame polymorphic forms A and G showing buildup and decay of magnetization as a function of contact time. (From Ref. l)...

When attempting quantitation of a mixture of polymorphs, the first step is to identify which peaks are due to each polymorph, and to select two well-resolved peaks corresponding to the same carbon in each polymorph. A multiple-contact time experiment is then acquired to determine the rates of magnetization transfer (7ch) and decay (Tip) for each form. If these rates are identical in each form, direct integration of the peaks will provide quantitative data, with the relative areas representing the amount of each form present in the mixture. An example of the results of a multiple-contact time experiment is shown in Fig. 2—a plot of the natural logarithm of relative peak area as a function of contact time for neotame forms A and It is clear from this plot that spectra acquired at any contact time will not give equal peak area for both forms. 

Fig. 3 CPMAS NMR spectrum of a 1 1 (wt/wt) mixture of neotame forms A and G. Inset shows expansion of the peaks used for quantitation, representing the same aromatic carbon in each polymorph. Relative peak areas are shown. (From Ref 1)...

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