Lecture_1 Equipment.pdf
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PHMD 1012 1 EXTEMPORANEOUS PHARMACEUTICAL COMPOUNDING Lecture 1 - Equipment OUTLINE: EQUIPMENT 1. BALANCES -PRESCRIPTION -ELECTRONIC DIGITAL -USE OF A BALANCE -WEIGHING...
PHMD 1012 1 EXTEMPORANEOUS PHARMACEUTICAL COMPOUNDING Lecture 1 - Equipment OUTLINE: EQUIPMENT 1. BALANCES -PRESCRIPTION -ELECTRONIC DIGITAL -USE OF A BALANCE -WEIGHING -TRITURATION -GEOMETRIC DILUTION 2. MORTARS AND PESTLES 3. SPATULAS 4. VOLUMETRIC GLASSWARE 2 Learning objectives… 3 1. Balances: Selection based on: Nature of material Quantity of material Accuracy required Prescription balance: May be beam on knife edge or torsion Every licensed pharmacy must have one Sensitivity represented by sensitivity requirement (SR) Courtesy: A Practical Guide to Contemporary Pharmacy Practice, 3e 4 1. Balances: SR is the weight which will cause a specified change Prescription balance requires SR of 6 mg 6 mg will cause a deflection of 1 unit on index plate Capacity usually 120 g Courtesy: Torbel balances 5 Electronic balances…. Use electromagnetic force to restore beam to neutral Electric current proportional to mass of object Very quick and easy to use Must be protected from electromagnetic fields May be affected by temperatures Wide range of capacity and sensitivity from 1mg to 300 g Courtesy: A Practical Guide to Contemporary Pharmacy Practice, 3e 6 Use of a balance: Should be kept on level solid surface Area free from vibration, air movement and dust Calibration Must be done when electronic balances moved Weight is the force gravity exerts on a mass Force of gravity varies with altitude 7 Error, accuracy and precision... Pharmaceuticals must be prepared with a low percentage of error Tolerance of ± 5% acceptable for most Accuracy is extent to which a measure agrees with true value % Error can be calculated from: Error of measurement % Error = 100% Quantity desired Error of measurement = measured value minus the desired value 8 Error of measurement- example Example: you intend to dissolve 6 g of drug A in 100 mL of water. You measured 100 mL of water in a graduated cylinder, but actual volume transferred was 98 mL due to error of parallax. Calculate the %error of measurement What is the % error in drug concentration 9 Error, accuracy and precision… If the sensitivity (potential error) of the balance is known, can calculate the % error when any amount is weighed from: Sensitivity % Error = 100% Quantity desired Similarly, can calculate the smallest quantity which can be weighed at a desired level of accuracy; lowest weighable quantity (LWQ). Very important concept Sensitivity LWQ = 100% % Error tolerated 10 Error, accuracy and precision… Accurate X Accurate √ Precise X Precise X 1 2 Accurate X Accurate √ Precise √ Precise √ 3 4 11 Trituration… Process of grinding a drug in a mortar with a pestle in order to reduce particle size or to blend powders May also refer to a blended mix of powders and the dilution of a potent drug with an inert diluent powder AJP Jan 2018 12 Trituration… Powders are mixed in a definite proportion by weight Allows removal of an aliquot (weighable quantity) which will contain the desired quantity of drug with acceptable accuracy Must always remember that any substance being weighed must exceed the lowest weighable quantity for the balance AJP Jan 2018 13 Geometric dilution… Process used when a small amount of material is to be mixed with a much larger amount of solid or semi-solid material Product homogeneity very important and this technique is effective for mixing Courtesy LP3 Network 14 2. Mortars and pestles: Utensils commonly used for small scale comminution Comminution is mechanical process of reducing particle size 15 2. Mortars and pestles: Mortars and pestles may be made of glass or porcelain Glass for soft powders, liquid incorporation or semi-solids like ointments, when communition is not desired Glazed porcelain similar to glass but Wedgewood somewhat rougher Wedgewood or Porcelain for comminution of crystalline material and for primary emulsions Glass or glazed porcelain best for colored material and volatile oils 16 3. Spatulas: May be made of stainless steel or plastic Steel should not be used with: * Materials like iodine or strong acids which could corrode the metal Materials where trace amounts of metal may be harmful to the product Drugs or materials which oxidize easily such as phenol * Modern stainless steel is usually not a problem 17 3. Spatulas: Primarily used for mixing cream or ointments 18 Levigation… Process of mixing powder with small amount of liquid (levigating agent) in which the powder is insoluble to make a smooth paste Agent aids in wetting of powder Used to reduce particle size and break down aggregates Often done with flexible spatula on a glass slab Can also be done in a mortar 19 4. Volumetric glassware: Used to measure exact quantities of liquids All are marked with capacity and have calibration marks for measuring May be ‘to deliver’ (TD) or ‘to contain’ (TC) Pipettes are TD while cylindrical graduates and volumetric flasks are TC Although Erlenmeyer flasks, beakers and prescription bottles may have graduate markings, they are NOT volumetric and should not be used for measuring 20 Pipettes… Used to measure volumes smaller than 5 mL Volumetric delivers a fixed volume while Mohr delivers variable volumes measured from near the tip to the nominal capacity of the pipette Should be filled using a bulb – mouth-pipetting is both unacceptable and dangerous Mechanical or autopipettes becoming more common 21 Syringes… Variety of nominal sizes from 0.5 to 60 mL Good accuracy Available for both parenteral and oral use Courtesy: Becton-Dickinson 22 Volumetric flasks… Used to prepare specific volumes Sizes range from 1 to 5000 mL Courtesy: Wikipedia 23 Graduated cylinders… Used for measuring and transferring liquids when the volume is greater than about 2 mL May be made of glass or plastic May be cylindrical or conical but cylindrical has better accuracy and conical are rarely used today When measuring liquids must use device most appropriate to volume being measured; a general guide is that the volume being measured must be at least 20% of the capacity. Courtesy: Wikipedia 24 Graduated cylinders… When measuring, the level of liquid to the mark should be measured at eye level and to the bottom of the meniscus to avoid error of parallax Courtesy: Wikipedia
