Quantitative nuclear magnetic resonance analysis of solid formoterol fumarate and its dihydrate.
Carbon-13 cross-polarization magic-angle spinning nuclear magnetic resonance spectra of anhydrous formoterol fumarate and the dihydrate are presented, together with some relaxation time measurements. The latter enabled quantitation of mixtures of the anhydrate and dihydrate to be made. Quantitative nuclear magnetic resonance measurements were then performed on mixtures of the two forms formulated in lactose. Relative amounts of the forms could be assessed at a total formulation level of 2%, whereas the dihydrate on its own in lactose was detectable at the 0.45% level. The optimum experiment involves dipolar dephasing, because that minimizes the intensity of signals from the lactose.
Apperley
David C
DC
Department of Chemistry, University of Durham, South Road, Durham DH1 3LE, United Kingdom.
Harris
Robin K
RK
Larsson
Tomas
T
Malmstrom
Torsten
T
D004983:Ethanolamines / Q000032:analysis* / Q000737:chemistry*; D000068759:Formoterol Fumarate; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*
D004983:Ethanolamines; D000068759:Formoterol Fumarate