Solvent evaporation kinetics in spray drying and how to consider heat loss

Author(s):  
Claudius Weiler ◽  
Christian Budde ◽  
Jörg Schiewe
1995 ◽  
Vol 398 ◽  
Author(s):  
I.J. Ford

ABSTRACTThe spray drying of a droplet containing a substance in solution can produce solid particles with a variety of final shapes: hollow, punctured, squashed, as well as solid spheres. The geometry affects the properties of the product. Models are presented here which describe the processes of solvent evaporation and solute crystallisation as drying takes place. The formation of a crust on the surface of the droplet is addressed. It is proposed that such a crust with a thickness of two crystallite diameters can develop into dry hollow shell. Some example calculations of the spray drying of droplets of sodium chloride solution are described.


Author(s):  
SILVIA SURINI ◽  
NADIA HUSNUL KHOTIMA

Objective: Tocotrienol is a natural Vitamin E compound with greater antioxidant activity than tocopherol. However, tocotrienol is considered unstable,which limits its handling and use in various product formulations. In this study, to enhance the stability of tocotrienol, tocotrienol oil was convertedinto a powder through a microencapsulation method using ethylcellulose (EC) as the coating material.Methods: Tocotrienol microcapsules were formulated with EC in ratios of 1:2 and 1:3 by solvent evaporation (SE) and spray drying techniques.The obtained microcapsules were then characterized in terms of shape and morphology, particle size, entrapment efficiency, percentage yield,flow properties, water content, swelling, and drug release. In addition, stability studies at both room temperature and elevated temperatures wereperformed.Results: Our results demonstrated that the tocotrienol microcapsules were of a white-yellowish powder of irregular shape, with particle sizes between1 μm and 60 μm and entrapment efficiency of 21.60% and 99.75%. After 12 weeks of storage at room temperature, the remaining level of tocotrienolin the microcapsules was 96.46–97.74%. In the accelerated stability study at elevated temperatures, the resulting k25 values ranged from 1.02×10-5 to1.32×10-5/h. Thus, the predicted shelf-life (t90) of the microencapsulated tocotrienol was determined to be between 11.01 and 14.27 months.Conclusion: The microencapsulation of tocotrienol with EC using SE and spray drying techniques produced a solid form of tocotrienol that wasconsiderably more stable than the natural form of tocotrienol.


Author(s):  
J P Raval ◽  
D R Naik

Designing and evaluating a multiparticulate controlled release dosage form, to increase the efficacy of acyclovir (a selective antiherpes agent). Spray drying technique for microsphere production is compared with novel solvent evaporation-matrix erosion technique for variable drug loading in different concentration of ethyl cellulose. The microspheres were characterized for physicochemical properties. The microspheres sizes were ranged from 7-25 μm. The spray dried microspheres had better encapsulation efficiency (up to 91%) compared to that of novel solvent evaporation-matrix erosion technique microspheres. Scanning electron microscopy confirmed spherical geometry due to high cross-linking density. Differential scanning calorimetry, Fourier-transform infrared spectroscopy and x-ray diffraction studies showed chemical stability and intactness of entrapped drug in the microspheres. In vitro release of acyclovir from spray dried microspheres continued for longer period compared to novel solvent evaporation-matrix erosion method. Overall, the release studies depended on the concentration of ethyl cellulose, extent of drug loading, and the technique used to prepare microspheres. Thus, marked retardation of drug release may provide a useful effective anti-retroviral drug therapy.  


2016 ◽  
Vol 34 (15) ◽  
pp. 1758-1772 ◽  
Author(s):  
Rameshwar Deshmukh ◽  
Pankaj Wagh ◽  
Jitendra Naik

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