Sedimentation and resuspendability evaluation of pharmaceutical suspensions by low-field one dimensional pulsed field gradient NMR profilometry

Abstract

In order to study the sedimentation of pharmaceutical suspensions using low-field one dimensional pulsed field gradient nuclear magnetic resonance (1D pfg NMR) profilometry, the accuracy of signal acquisition as well as the spatial resolution of a commercial spectrometer operating at 23.4 MHz was investigated. The use of a solid Teflon spacer revealed that the accuracy of signal acquisition was independent of spatial position (height). The standard deviation of distance determinations was less than 150 µm, whereas the accuracy of water content determination was within 2% in the central part of the detection zone and deteriorated to 4% in the outer parts. The study of aqueous paramagnetic MnCl₂ solutions indicated an exponential relationship between the relative signal intensity and the transverse relaxation decay constant. From this relationship, the relative water content of suspensions could be derived from their signal intensity relative to that of water. Using concentrated paliperidone palmitate dispersions as model suspensions, low-field 1D pfg NMR profilometry has been proven to be suitable for the evaluation of both the sedimentation and resuspendability behavior of viscous, opaque suspensions, for which visual detection of homogeneity may be difficult.

Keywords::

• Pulsed field gradient
• nuclear magnetic resonance
• suspension
• sediment characterization
• sedimentation
• resuspendability

Acknowledgments

Zhu Wuxin thanks Janssen Pharmaceutica for providing a Ph.D. scholarship.

Declaration of interest

The authors kindly acknowledge the financial support of the Research Foundation− Flanders (FWO) for the NMR spectrometer. The authors report no conflicts of interest.