What is solvent evaporation method?
In the solvent evaporation method, the drug is dissolved, dispersed, or emulsified into an organic polymer solution, which is then emulsified into an external aqueous or oil phase. The microspheres are formed after solvent diffusion/evaporation and polymer precipitation.
What type of organic solvent is used in solvent evaporation technique?
Commonly used solvents include methylene chloride (also called dichloromethane or DCM) (Singh et al., 2008), ethyl acetate (Cho and Sah, 2005), and acetone/methanol mixtures. The single emulsion technique is generally employed for synthesis of microparticles encapsulating hydrophobic drugs.
What are the types of microencapsulation technique polymerization?
15.4. 1 Microencapsulation mechanisms
| Category | Specific methods |
|---|---|
| Chemical method | Interfacial polymerization, in situ polymerization, piercing-solidifying |
| Physical-chemical method | Simple coacervation, complex coacervation, phase separation, drying bath, powder bed grinding, melting-dispersion-condensation, capsule-core exchange |
Which microencapsulation technique is known as Wurster process?
AIR SUSPENSION TECHNIQUES
AIR SUSPENSION TECHNIQUES (WURSTER) PROCESS: In this process, the drug particles are coated and dried while suspended in an upwardly moving current of air.
Which solvent evaporates the fastest?
Acetone evaporates faster than MEK and, in fact, is the fastest evaporating of all the solvents commonly available to consumers. It is used in many industries as a cleaner and degreaser.
What is solvent displacement method?
In solvent displacement method, the polymer is precipitated from an organic solution and the organic solvent diffuses in the aqueous medium in the presence or absence of surfactant. Semipolar water miscible solvent (acetone, ethanol) is used to dissolve polymers, drug, and or lipophilic surfactant.
What is double emulsion solvent evaporation method?
Formation of double emulsion (particulate dispersion) is followed by evaporation of the organic solvent (O) from the dispersed phase leading to a point of insolubility and consequently, hardening of the polymer encapsulating the active material.
What are the different methods of microencapsulation?
Large number of techniques for microencapsulation include spray chilling, spray cooling, fluidized bed coating, liposome entrapment, extrusion, freeze drying, and coacervation.
Which of the following method is used in microencapsulation?
(c) Spray drying and Spray congealing, both methods have been used for many years as microencapsulation techniques.
What is Wurster method?
The Wurster process is recognized as the technology for precision application of a film coating onto particulate materials such as powders, crystals, or granules, and other solid ingredients with diameters ranging from 30 µm to several centimeters.
What is the formula for evaporation?
The equation states that, the evaporation rate, W = (95+0.425*V)*(Pw-Pa)/Y, where W is the Evaporation rate in lb/h-ft2; V is the air velocity at water surface; ft/min; Pw is the saturation vapor pressure at water temperature, in. Hg; Pa is saturation vapor pressure at air dew point, in.
What is evaporation solvent rate?
Evaporation Rate – How fast the solvent will evaporate in given air flow. More usually described as Relative Evaporation Rate (RER) with respect to a standard solvent such as n-butyl acetate, nBuAc.
Which method is a displacement method?
The Displacement Method
From a system of equilibrium equations, the deformations can be calculated from which internal forces and reactions are calculated. The displacement method is superior to the force method when the number of unknown forces exceeds the number of unknown displacements and rotations.
What are the displacement methods?
The displacement method (submersion, or dunking method) can be used to accurately measure the volume of the human body and other oddly shaped objects by measuring the volume of fluid displaced when the object is submerged, as illustrated in the figure below.
What is double emulsion used for?
Double emulsions are used in a range of industries, most usually Pharmaceuticals, Food and Cosmetics, to protect or isolate sensitive ingredients.
What are double emulsions?
Definition. Double emulsions are liquid dispersion systems known also as emulsions of emulsions, in which the droplets of one dispersed liquid (emulsion, microemulsion, liposome, etc) are further dispersed in another liquid (water or oil), producing double layered liquid droplets.
What are the types of microcapsules?
Different types of microcapsules: (i) simple microcapsule, (ii) matrix (microsphere), (iii) irregular microcapsule, (iv) multicore microcapsule, (v) multiwall microcapsule, and (vi) assembly of microcapsule.
What are micro encapsulation used for?
Microencapsulation is used to reduce adverse aromas, volatility, and reactivity of food products and to provide food products with greater stability when exposed to adverse conditions (e.g., light, O2, and pH) [5, 6].
What is the size range of microencapsulation?
The size of the obtained microcapsules is in the range of 35–5000 μm, with the upper value having no size limit with respect to the technological process, but with respect to the microparticle system. Various mechanical means are used for microencapsulation using centrifugal force.
Which technique is used for coacervation micro encapsulation technique?
Microencapsulation technology for smart textile coatings
Phase coacervation is one of the oldest and most widely used techniques of microencapsulation and can be divided into two groups: simple coacervation, which implies the use of one colloidal solute such as gelatine, chitosan, etc.
What is fluidized bed coating?
Fluidized bed coating or granulation is a process by which granules or coated particles are produced in a single piece of equipment by spraying a binder as solution, suspension, or melt onto a fluidized powder bed. This process is sometimes classified as the one-pot system.
Which of the following are components of microencapsulation?
Simply defined, microencapsulation involves the coating of a substance with a protective material, usually a polymer, such that small particles of less than about 1 mm are formed. Terms commonly used to describe the microencapsulated substance include core material, active agent, internal phase, and fill.
What is the unit of evaporation?
Units. The evapotranspiration rate is normally expressed in millimetres (mm) per unit time. The rate expresses the amount of water lost from a cropped surface in units of water depth. The time unit can be an hour, day, decade, month or even an entire growing period or year.
What is the factors affecting evaporation?
Factors affecting evaporation:
- Temperature: On increasing the temperature the rate of evaporation also increases.
- Wind speed: Wind speed and rate of evaporation are directly proportional to each other.
- Surface area: As the surface area increases, the rate of evaporation also increases.
- Humidity:
What is evaporation process?
Evaporation is the process that changes liquid water to gaseous water (water vapor). Water moves from the Earth’s surface to the atmosphere via evaporation. Evaporation occurs when energy (heat) forces the bonds that hold water molecules together to break.