Influence of Particle Size on the Ultraviolet Spectrum of Particulate-Containing Solutions: Implications for In-Situ Concentration Monitoring Using UV/Vis Fiber-Optic Probes

Abstract

For solutions containing small (submicron) felodipine particles, UV spectra were influenced by absorption of the particles and contributions from absorption of dissolved molecules and scattering of the particles. Caution should be applied when using in situ UV/VIS-probes to monitor the amount of dissolved material during dissolution, in particular when small particles are present (e.g. dissolution of nanoparticulate formulations) or generated (e.g. precipitation of supersaturated solutions) in the dissolution medium.

Evaluation of the Microcentrifuge Dissolution Method as a Tool for Spray-Dried Dispersion

“…Previous studies had been reported on the parameters affecting supersaturation such as temperature (13,14). Reports have shown that the supersaturation profiles are affected by the changes of drug load in SDD (11,15,16,17). The studies we presented here show that supersaturation profiles are affected by the revolutions per minute speed of centrifuge, the centrifuge time, the filtration of supernatant.…”

Impact of Solubilizing Additives on Supersaturation and Membrane Transport of Drugs

“…Ultraviolet (UV) extinction measurements (4,21,25) were used to evaluate the phase behavior of felodipine and nifedipine at different solution concentrations. Felodipine and nifedipine were dissolved in methanol to obtain a drug stock solution of 20 mg/mL.…”

“…In addition, at very high supersaturations, a non-crystalline drug-rich may be formed (17)(18)(19). Formation of a disordered drug-rich phase has been widely observed during dissolution of amorphous solid dispersions (20)(21)(22)(23)(24)(25)(26). Certain polymers are believed to facilitate formation of this disordered phase by inhibiting crystallization and can stabilize the resultant drugrich phase in the nano-sized regime (23,24).…”

Using Environment-Sensitive Fluorescent Probes to Characterize Liquid-Liquid Phase Separation in Supersaturated Solutions of Poorly Water Soluble Compounds

“…Several techniques are currently employed to detect and characterize LLPS. Light scattering techniques such as static light scattering (19,20), quasi-elastic light scattering or dynamic light scattering (20) as well as extinction measurements (14,21) have been used to examine self-association or aggregation in small molecules. Other techniques that have been used include scanning electron microscopy and polarized light microscopy (PLM) (14,22).…”