  In this work we propose the Nuclear Quadrupole Resonance (NQR) technique as
an analytical method suitable for polymorphism detection in active parts (or
active principles) of pharmaceuticals with high pharmacological risk. Samples
of powder carbamazepine (5H-dibenz(b,f)-azepine-5-carboxamide) are studied. In
its anhydrous state, this compound presents at least three different
polymorphic forms: form III, the commercial one, form II, and form I. Of these,
only form III possesses desirable therapeutic effects. By using the NQR
technique, it was possible to characterize two of the three polymorphic phases
(I and III) for anhydrous carbamazepine in few minutes at room temperature,
detecting the characteristic frequencies of 14N nuclei (I=1) present in their
chemical composition and in the frequency range 2.820-3.935 MHz. For form II,
characteristic lines were not detected within this range of frequencies. The
lines detected for form III are centered at the frequencies \nu_{1}^{III}=3.876
MHz, \nu_{2}^{III}=3.829 MHz, and \nu_{3}^{III}=2.909 MHz; and for form I
centered at \nu_{1}^{I}=3.876 MHz, \nu_{2}^{I}=3.840 MHz, \nu_{3}^{I}=2.911
MHz, and \nu_{4}^{I}=2.830 MHz.
