Rapid Quantitative GLC Analysis of Digoxin

X-ray Diffraction of Water in Polyvinylpyrrolidone

“…A two-phase exponential increase in water sorption is found with time but becomes stretched at longer times. The final water contents correspond to (a) ∼0.5 wt % water with 1 H 2 O molecule to 34 PVP monomers for 35% RH 27 °C for 30 h and (b) ∼0.8 wt % water with 1 H 2 O molecule to 22 PVP monomers at 75% RH 40 °C for 50 h. These values are considerably lower than the equilibrium moisture contents of ∼6 wt % water at 35% RH and 25 °C and ∼30 wt % at 75% RH and 40 °C . Diffusion measurements on PVP films have found an initial diffusivity of ∼10 –8 cm 2 /s for < 0.1 wt % H 2 O, rising to ∼10 –6 cm 2 /s at 0.3 wt % H 2 O .…”

“…The EPSR simulation for pure PVP was performed on 50 PVP K15 molecules (comprising of 5 repeat units) using a cubic box under periodic boundary conditions, using an atomic number density of 0.118 atoms Å –3 , corresponding to a cubic box size of ∼30 Å. The K -value denotes the approximate molecular weight for different grades of polymer by using viscosity in aqueous solution relative to water, calculated using Fikentscher’s equation. , We note that although the nominal density of PVP (ρ = 1.18 g cm –3 ) corresponds to 0.109 atoms Å –3 , this had to be refined in order to get a good fit between the EPSR model and the X-ray data for dry PVP in the region of first few intramolecular peaks in the X-ray PDF. The X-ray consistent density of dry, amorphous PVP was found to be 0.118 atoms Å –3 (1.28 g cm –3 ) significantly higher than the nominal value.…”

“…Hydration studies were performed on Kollidon 15PF (BASF used as received), which has ∼6% water content at 10% RH and 25 °C, a nominal bulk density of 1.18 g/mL, and average molecular weight of 8000 . Powder was pressed into a ca.…”

“…The hydrophilic nature of PVP has been widely characterized and is largely independent of molecular weight; PVP can absorb up to ∼45% by weight at 80% humidity at room temperature . Assimilation of ambient water is useful to solubilize a product but also can lead to unwanted degradation that can decrease the efficacy of an amorphous formulation.…”

“…Polyvinylpyrrolidone (PVP, povidone, trade name Kollidon) is one of the most important substances in the pharmaceutical and cosmetic industries. − PVP is a highly soluble amorphous polymer consisting of a repeating chain of linear 1-vinyl-2-pyrrolidinone groups (C 6 H 9 NO) n and is widely used as an excipient to enhance the solubility and bioavailability of an active pharmaceutical ingredient in amorphous solid dispersions. , The PVP polymer matrix traps the active pharmaceutical ingredient to inhibit crystallization at the molecular level, , which can alter the product’s physical properties and chemical stability and lead to an increased dissolution rate of the orally administered drug in the gastrointestinal tract. − Due to PVP’s excellent wetting properties it is commonly used as a binder in the manufacture of tablets, granules, capsules and in coating processes. PVP is also used in formulation matrices to provide controlled release dosages, including in treatments for COVID-19 …”