Loren J Schieber | PubMed Health

PubMed2006

Investigation of solid-state NMR line widths of ibuprofen in drug formulations.

Solid-state nuclear magnetic resonance spectroscopy (SSNMR) line widths were measured for various ibuprofen preparations, including crystallization from different solvents (acetone, acetonitrile, methanol), melt-quenching, manual grinding, cryogrinding, compacting, and by blending with various excipients. Ibuprofen recrystallized from acetonitrile exhibited broader lines than ibuprofen recrystallized from either acetone or methanol. Manually ground ibuprofen had SSNMR line widths that were indistinguishable from the commercial sample, but cryoground ibuprofen had larger line widths than either. Physical mixtures with most excipients decreased the SSNMR line widths. Only dilution in talc led to line width increases, which is attributed to the magnetic susceptibility anisotropy of the talc excipient. Our results show that SSNMR line widths can be used to understand physical characteristics including particle size and morphology, degree of order in the materials, and physical environment.

Chemistry, Pharmaceutical↗

PubMed2005

Multiple-sample probe for solid-state NMR studies of pharmaceuticals.

Solid-state NMR spectroscopy (SSNMR) is an extremely powerful technique for the analysis of pharmaceutical dosage forms. A major limitation of SSNMR is the number of samples that can be analyzed in a given period of time. A solid-state magic-angle spinning (MAS) probe that can simultaneously acquire up to seven SSNMR spectra is being developed to increase throughput/signal-to-noise ratios. A prototype probe incorporating two MAS modules has been developed and spectra of ibuprofen and aspirin have been acquired simultaneously. This version is limited to being a two-module probe due to large amounts of space required for the tuning elements located next to the MAS modules. A new probe design incorporating coaxial transmission lines and smaller MAS modules has been constructed. This probe allows for close proximity of the MAS modules (within 3 cm), adequate proton decoupling power (>50 kHz), and the capability of remote tuning and sample changing. Spectra of hexamethylbenzene (HMB) have been acquired and show signal-to-noise ratios comparable to existing SSNMR probes. Adamantane line widths are also comparable to conventional probe technology. Decoupling powers of 70 kHz have been achieved using a MAS module suitable for 3 cm spacing between modules. Remote tuning has also been achieved with this new coaxial transmission line design. This probe design can be easily scaled to incorporate multiple MAS modules, which is a limitation of the previous design. The number of modules that can be incorporated is only limited by the number of transmission lines that will fit in a cross-sectional diameter of the bore and the axial field length of the magnet.

Complex Mixtures↗