NQR frequencies of anhydrous carbamazepine polymorphic phases

الأصل · EN

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 ν₁III=3.876 MHz, ν₂III=3.829 MHz, and ν₃III=2.909 MHz; and for form I centered at ν₁ⁱ=3.876 MHz, ν₂ⁱ=3.840 MHz, ν₃ⁱ=2.911 MHz, and ν₄ⁱ=2.830 MHz.