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The Human Nail: Structure, Properties, Therapy and Grooming
Published in Heather A.E. Benson, Michael S. Roberts, Vânia Rodrigues Leite-Silva, Kenneth A. Walters, Cosmetic Formulation, 2019
Kenneth A. Walters, Majella E. Lane
Dynamic vapour sorption is a gravimetric method for studying the sorption properties of materials under controlled conditions of temperature and humidity. Recently we evaluated the sorption properties of human nails in a specialised DVS apparatus, which was also fitted with an NIR probe (Walters et al., 2012). Nail clippings from six volunteers were subjected to a fixed temperature of 32°C and a range of relative humidity values, ranging from 40% to 90%, with 10% increments. The increase in the relative humidity (40–90%) was associated with a linear change in mass profile. The NIR spectra also indicated increases in band absorbance (second derivative spectra) at 1422 nm and 1908 nm. Good correlations (Figure 5.3 ) were obtained for the gravimetric changes and band absorbances at 1422 nm and 1908 nm.
Solid State Testing of Inhaled Formulations
Published in Anthony J. Hickey, Sandro R.P. da Rocha, Pharmaceutical Inhalation Aerosol Technology, 2019
Philip Chi Lip Kwok, Hak-Kim Chan
Dynamic vapor sorption can be performed to examine solid-water interactions by monitoring the mass change of the sample as a function of RH. The RH is programmed to step up and down sequentially at a constant temperature to obtain sorption-desorption isotherms (Ward and Schultz 1995, Buckton and Darcy 1995). The sample mass increases and decreases during the sorption and desorption phases, respectively. Water absorbed into amorphous regions may act as a plasticizer and lowers the glass transition temperature. This may trigger the recrystallization of these regions and results in a sudden mass loss due to the partial desorption of water upon the formation of crystalline regions, which have lower water affinity than their amorphous counterparts. The recrystallization event can be verified by running the sample through two sorption-desorption cycles. If the recrystallization of amorphous regions was completed in the first cycle, then the corresponding mass loss should not recur in the second cycle. The sample should also be less hygroscopic in the second cycle because it is crystalline (Ward and Schultz 1995).
Data-driven approach to mitigate quality impact of hygroscopic pharmaceutical raw materials throughout the supply chain
Published in Pharmaceutical Development and Technology, 2022
Mary K. Chaves, Ron C. Kelly, Jacqueline E. Milne, Susan E. Burke
Moisture sorption data to determine the hygroscopicity classification was collected using a DVS Endeavor (Surface Measurement Systems) dynamic vapor sorption (DVS) analyzer. Samples (∼100 mg) were evaluated in an aluminum pan by equilibrating at 30% RH (equilibration set to a dm/dt of 0.001% wt/min with a minimum of 10 min and maximum of 3 h), then an intermediate step at 65% RH (equilibration set to a dm/dt of 0.001% wt/min with a minimum of 10 min and maximum of 3 h) then the final hold at 80% RH (for 24 h) at 25 °C with a nitrogen flow rate of 500 sscm. Equilibrium was not always achieved during this final 24 h hold. The increase in mass from the end of the 30% RH step to the end of the 80% RH step was used to assign the hygroscopicity classification (‘H-1′ to ‘H-4′) according to Table 1 unless otherwise noted in the result tables. The qualitative term of ‘hygroscopic materials’ used in this manuscript includes materials classified as hygroscopic (H-3) or very hygroscopic (H-4). Since the end of the 30% RH step is the zero point (or baseline), any weight loss/gain recorded during the 30% RH step is additive to the weight gain at 80% RH. In some cases (evaporative liquids), the experiment was started at 80% RH as noted in the data tables to avoid evaporation at lower humidity.
The role of the solid state and physical properties of the carrier in adhesive mixtures for lung delivery
Published in Expert Opinion on Drug Delivery, 2018
Andrea Della Bella, Enrico Salomi, Francesca Buttini, Ruggero Bettini
Indeed, techniques such as powder X-Ray diffraction and differential scanning calorimetry, which are commonly used for the characterization of pharmaceutical solids, are not sufficiently discriminating to identify the solid-state changes induced by processing. Newly formed phases might be generated in quantities that are considerably lower than the detection limit of the analytical techniques. Additionally, distinctive signals could be partially or totally overlapped to those of the starting material, thus resulting hardly observable. In this respect, dynamic vapor sorption, nuclear magnetic resonance, or Raman spectroscopy (in particular when coupled with confocal microscopy) may represent more suitable technique allowing for higher resolution and more accurate detection of the crystalline composition of the solid under investigation.
Comparison study of physicochemical and biopharmaceutics properties of hydrophobic drugs ground by two dry milling processes
Published in Pharmaceutical Development and Technology, 2022
M. Dandignac, S. P. Lacerda, A. Chamayou, L. Galet
The dynamic vapor sorption measurements were carried out on the DVS apparatus of the SMS (Surface Measurement Systems) (Allentown, PA). All experiments were performed at 25 °C. Dry nitrogen is blown through the probe for 60 min. The relative pressure of the probe is controlled using a computer program that sets the appropriate flow rate on the wet side (100% relative pressure of the probe) and the dry side (dry nitrogen). Fifty to 100 mg was placed into the pods. Measurements were recorded on a scale from 0 to 95% relative humidity (RH) with a measurement step of 10% RH. The final step was set at 95% RH. Two measurement cycles were conducted.