Lecture 1 Pharmaceutical Technology I.pdf

Pharmaceutical Technology I PIP 418 By Prof. Mahmoud Soliman  Extraction Objectives: By completing this chapter, the students will able to: - Define the extraction process. - Acquire knowledge about the factors affecting extraction process. - Identify Types of ext...

Pharmaceutical Technology I PIP 418 By Prof. Mahmoud Soliman  Extraction Objectives: By completing this chapter, the students will able to: - Define the extraction process. - Acquire knowledge about the factors affecting extraction process. - Identify Types of extraction process. - Acquire knowledge about Extraction Equipment.  Extraction (Defnition) Extraction is the removal of soluble material from an insoluble residue, either solid or liquid, by treatment with a liquid solvent (Menstruum). It is a mass-transfer process depending on the rate of diffusion of solute through the liquid boundary layer or layers at the interface. Tinctures (1 herb: 3 solvent), and Extracts (1 herb: 1 solvent) are the pharmaceutical products most commonly prepared from extractives.  Extraction ❑Crude drug contains a number of constituents that may be soluble in a given solvent, so the products of extraction do not contain just a single constituent but rather varying constituents, depending on the drug used and the conditions of the extraction. ❑The solvent systems used in extraction are selected on the basis of: Their capacity to dissolve the maximum amount of desired active constituents The minimum amount of undesired constituents. Extraction (Types)  The Choice of Extraction Method in Leaching Process ❑The choice of extraction method depends primarily on: 1. The physical properties of the extracted material. 2. The particle size of extracted material. I- For the coarse and rigid material which forms highly permeable bed, percolation is operated. The use of pressure extends the application of percolation to materials that form beds of low permeability. Alternatively, permeability may be increased by grinding the solids with a supporting material such as glass wool.  The Choice of Extraction Method II- For fine powders or compressible animal tissues that will not form permeable beds, Immersion is operated. The use of finer powders provides intimate contact between solids and liquid and prevents channelling which gives a more rapid and more complete extraction. But this is associated with difficulties of separation and the dilution of the extract during washing. Examples of Solvent  Examples of Solvent 1- Water and alcohol, and mixtures of the two are widely used. Both are nonselective leaching varying proportions of gums, mucilages, and other unwanted components. Acidified or alkaline mixtures of water and alcohol are used to extract insulin from minced pancreas. Most of the tinctures and liquid extracts used in pharmacy are simple, impure extracts made with water or mixtures of water and alcohol. 2- Petroleum solvents and benzene. Used for selective extraction of many alkaloids Subsequent purification by fractional crystallization is facilitated by the absence of gums. Factors Affecting The Rate of Leaching  1- The size and size distribution of the solid particles ❑Decreasing particle size by grinding induced the following: 1. Reduced the distance of diffusion and greatly increases the rate of leaching. 2. Increased the surface area of contact between the matrix and the surrounding liquid. 3. Increased the concentration gradient. 4. Facilitates the transfer of solute at the boundary layer ❑ But the extraction of very fine materials associated with difficulties in the separation of solid and liquid after extraction.  1- The size and size distribution of the solid particles ❑The optimum particle size for any particular extraction is determined by the physical nature of the solids. For example: A dense, woody structure would be extracted as a fine powder. A leafy structure would be more satisfactorily leached as a coarse powder.  1- The size and size distribution of the solid particles ❑Advantages of the narrow size distribution of solid materials: 1) It promotes high porosity for the bed. 2) It gives even packing and creates a regular system of pores. 3) It promotes even movement of solvent and solution through the bed. ❑After grinding, it is necessary to classify the product and remove undersize material. As the small particles may otherwise fill the interstices created by the contact of larger particles.  2- Temperature ❑The increase in temperature increases the solubility of most materials and consequently achieved higher solute concentrations and higher concentration gradients. ❑Both higher solute concentrations and higher concentration gradients increase diffusivity and consequently give higher extraction rates. ❑ In many cases, however, materials are susceptible to heat degradation, and cold extraction must be used as in case of enzymes or thermolabile materials.  3- The physical properties of solvents ❑The ideal solvent should be: 1) Cheap, nontoxic, and non-inflammable. 2) It is highly selective, dissolving only the wanted constituents of the solid. 3) It should have a low viscosity, allowing easy movement through a bed of solids. 4) It should have a high vapor pressure, allowing easy concentration of solution by evaporation.  4- Agitation ❑Up to a certain limit, agitation of the solvent increases the diffusion and, therefore, increases the transfer of material from the surface of the particles to the bulk of the solution. ❑ More agitation will not affect diffusion of the solute from the cell matrix to the outside. ❑The major and controlling resistance to the diffusion of the solute to the bulk solution is normally found in the cell matrix.  I- Solid- Liquid extraction “Leaching” ❑Leaching: Is the extraction of a soluble constituent from a solid by a solvent. ❑The extracted liquid is sometimes called the miscella, and the exhausted solids are called the marc. ❑Application of leaching process: 1) The extraction of fixed oils from seeds/bark, e.g extraction of strychnine from Nux vomica beans, and quinine from Cinchona bark. 2) The isolation of enzymes, such as renin, from animal sources 3) The isolation of hormones, such as insulin, from animal sources.  I- Solid- Liquid extraction “Leaching” ❑Limitations of Leaching 1) In the pharmaceutical industries Leaching is usually operated as a batch process, since high- cost materials are processed in relatively small quantities. 2) Frequent changes of material may be made, creating problems of cleaning and contamination.  A- Leaching By Percolation ❑Notes: Soaking may precede the movement of liquid. The packing must be even to ensure efficient leaching. Temperature The body of the extractor may be jacketed to give control of the extraction temperature. Closed extraction vessels are used for high-temperature extraction and extraction with volatile solvents. Bed permeablity In the highly permeable bed, the solvent is moved by simple gravity. But in the dense bed, the solvent is pumped through the bed if suitable flow rates are to be secured.  A- Leaching By Percolation ❑When extraction is carried out by sprinkling the solvent (menstrum) on the upper surface of the bed, it requires large amounts of solvent and yield dilute extracts. Therefore, the extraction is followed by evaporation and the vapor leaving the evaporator is condensed and returned to the extractor. ❑These operations are often integrated in extraction plant. The leach liquids leaving the extractor enter an evaporator heated, for example, by a calandria. For heat sensitive materials, this will be operated at reduced pressure. ❑Advantages of Leaching by percolation: It provides a simple method of separating leach liquid and solid during the extraction  1- Stationary- bed (Batch percolator) It is suitable for the preparation of concentrated alkaloid extracts by percolation. ❑The packing of the coarsely ground material must be even. ❑Channelling is prevented or reduced by placing horizontal perforated plates at intervals in the bed. ❑Simple extractions of this type will require large amounts of solvent and yield dilute extracts. Therefore, extraction followed by evaporation. Batch percolator https://www.youtube.com/watch?v=wC2L7dd VXZI&embeds_referring_euri=https%3A%2F%2 Fwww.cgtrader.com%2F&source_ve_path=OTY 3MTQ 2- Moving- bed (Bollman extractor)  2- Moving- bed (Bollman extractor) 1 ❑ The solids are moved through the solvent with little or no agitation, and the process of extraction is made continuous. ❑ The Bollman Extractor, or Hansa Mühle, contains a perforated bucket-, or basket- elevator in a closed casing. 2 ❑ At the top right-hand corner 1 of the machine, the buckets or baskets are loaded with flaky solids, and are sprayed with appropriate amounts of "half miscella" as they travel downward 2. As solids and solvent flow concurrently down the right-hand side of the machine, the solvent extracts more oil from the solids. 3 ❑ Half miscella is the intermediate solvent containing some extracted oil and some small solid particles 3.  2- Moving- bed (Bollman extractor) ❑ Simultaneously, the fine solids are filtered out of the solvent, giving a clean "full miscella" from the right hand sump at the bottom of the casing 4. 6 ❑ As the partially extracted solid rise 3 through the left side of the machine, a 5 stream of pure solvent percolates counter- currently through them 5. It collects in the left-hand sump and is pumped to the half- miscella storage tank 3. ❑ Fully extracted solids are dumped from the buckets at the top of the elevator into a hopper 6. 3 4 ❑ The capacity of typical units is 50 to 500 tons of beans per 24-hours.