Vacuum drying systems, properties

Brouwer T, Todd DB et al (2002) Flow characteristics of screws and special mixing enhancers in a co-rotating twin screw extruder. Int Polym Process 17(l) 26-32 Carpenter J, Katayama D et al (2009) Measurement of Tg in lyophilized protein and protein exdpient mixtures by dynamic mechanical analysis. J Therm Anal Calorim 95 881-884 Chiang P-C, Ran Y et al (2012) Evaluation of drug load and polymer by using a 96-well plate vacuum dry system for amorphous solid dispersion drug delivery. AAPS Pharm Sci Tech 13(2) 713-722 Chokshi RJ, Sandhu HK et al (2005) Characterization of physico-mechanical properties of in-domethadn and polymers to assess their suitability for hot-melt extrusion process as a means to manufacture sohd dispersion/solution. J Pharm Sci 94(11) 2463-2474... 

Citrate method The preparation procedure consisted in the dissolution of the metal salts, namely Mn(N03)2 4H20 and Ce(N03)3 6H20, in distilled water, the complexation of the metallic cations with citric acid and the rapid concentration of the liquid by evaporation under vacuum. The viscous liquid was dried at 80°C and the amorphous precursor obtained was decomposed in air prior to calcination. Owing to the complexing property of the citrate anion, this procedure leads to the formation of finely dispersed two-phase systems or favours the formation of mixed oxide phases upon calcination, when these exist. Samples were calcined for 5 hours at 200, 300,400 or 500°C. 

Moisture content was determined by drying them under vacuum to constant weight at 60°C (AOAC, 1980). Water activity was measured at 25°C by using a Decagon Cx-3 (Aqualab) hygrometer. Mechanical properties of dried samples with different water content were analyzed at 30°C by using a puncture test with a Universal Texture Analyser (TA.XT2, Stable Micro Systems). A cylindrical 2.0 mm diameter pimch was used at a penetration rate of 1.5 mm/sec until total sample penetration. Determinations were made in five different samples with the same water content. 

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