Fourier transform infrared (FTIR) spectrometry for the assay of polyhedral boron compounds in plasma and pharmaceutical formulations.

The determination of polyhedral boron compounds such as sodium borocaptate directly in blood plasma is described using FTIR with computed nonlinear background subtraction of the water absorption band. The procedure can be performed in less than 15 min to a sensitivity level of 5 ppm boron (as a signal/noise ratio of 2.5), which is satisfactory in the clinical application of such compounds in neutron capture therapy of cancer. For boron compounds with suitable organic solubility, extraction from plasma into carbon tetrachloride is described as an alternative approach not requiring computed subtraction and capable of achieving a sensitivity level of 1 ppm. Both the boron and the lipid content of liposome formulations containing the polyhedral boron compounds can be measured simultaneously by FTIR. After extraction into CHCl3:CH3OH (1:1) or dispersion in ethanol, the extracts are evaporated to dryness and redissolved in carbon tetrachloride for FTIR assay.