Physical Pharmacy Lecture 1 PDF

Faculty of Pharmacy & Drug Manufacturing PHYSICAL PHARMACY 1  Course Specifications Program(s) on which the course is given: Pharm D Clinical & Pharm D. Major or Minor element of programs: Pharmaceutics. Department...

Faculty of Pharmacy & Drug Manufacturing PHYSICAL PHARMACY 1  Course Specifications Program(s) on which the course is given: Pharm D Clinical & Pharm D. Major or Minor element of programs: Pharmaceutics. Department offering the program: Department of Pharmaceutics. Department offering the course: Department of Pharmaceutics & Ind. Pharmacy Basic Information: Course Name: Physical Pharmacy Course Code: PT 202 Total Credit hours: 3 hrs Lecture: 2 hrs Tutorial/Practical: 1 hrs 2  Calendar for the 2nd Term of The Academic Year 2019/2020 Subject Items Surface Tension Surface tension, attraction forces, adhesive forces and cohesive forces Surface active agents, structure of surfactants and classification of surfactants with examples. HLB system Critical micelle concentration (CMC), structure of micelles and factors affecting micelle formation and CMC. Pharmaceutical applications of surface active agents. Polymorphism Def. of polymorphism. Crystal Structure and External Appearance Pharmaceutical Implications of Polymorphism. Crystal solvates, crystal hydrates, polymorphic solvates and peudopolymorphic solvates. Differences between crystal solvates and anhydrates. Solubility Def. of solubility, solution, Saturated, Unsaturated (subsaturated) and Supersaturated. Solubility expressions (Qualitative expressions and Quantitative expressions including Percentage, Molarity, Normality and Molality). Types of solutions. Factors Affecting Solubility of solids in liquids. Factors Affecting Solubility of gases in liquids and Henry's law. Solubility of liquids in liquids (Ideal Solutions Non-ideal solutions = Real solutions). Raoult’s Law. Diffusion & Dissolution Def. of Diffusion. Fick’s first law of diffusion. Fick’s second law of diffusion. Absorption from biological membranes. 3  Calendar for the 2nd Term of The Academic Year Subject Items Collegative properties What are Colligative properties of a solution? Explanations of colligative properties. Applications of colligative properties. Buffer Solutions Buffer solutions, Buffer Action How a mixture of a weak base or a weak acid and its salt will behave? Henderson-Hasselbach equation for acidic and basic buffer solutions. Buffer capacity Factors Affecting pH of buffer Solutions Biological Buffers Applications of Pharmaceutical Buffers Buffered Isotonic Solutions Adsorption Def. of Adsorption, Sorption and Desorption. Types of Adsorption. Factors affecting adsorption. Adsorption Isotherm Pharmaceutical Applications of Adsorption Rheology Def. of rheology, tensile strength, shearing stress and types of deformation. Newtonian flow and Non-newtonian flow (Plastic, pseudoplastic and dilatant flow) Def. of Viscosity, Kinmatic viscosity, specific viscosity and relative viscosity. Thixotropy, irreversible thixotropy and rheopexy Pharmaceutical applications of rheology Partition Co-efficient Def. of partition co-efficient. Factors affecting partition co-efficient. Applications of partition co-efficient. 4 Student assessment methods - Written final and quizzes to assess general understanding and basic knowledge - Oral exam to assess student understanding and ability to communicate and express their knowledge efficiently - Practical exams to assess the student’s abilities and skills in compounding and dispensing different dosage forms and solving problems of pharmaceutical calculations - Evaluation of each practical lesson to assess the student effective participation in class activities. 5 Assessment schedule 1st Quiz ………………………….....……………………………………………….…. week 2nd Quiz ………………………………………………..………………….……............ week Practical Exam ……………………………………...………………………....………..week Final Written Exam ……………………...................................................................…..week Oral………………………….....………………………………………………………. week Weighing of assessments Quizzes ………………………………….…………….……………………………….(15) marks Midterm ………………………………………………………………………...……. (15) marks Practical ………………………………………………………………………...……. (20) marks Final – term examination ……………………………………..…………...…………. (40) marks Oral ……………………………………………………………………..……….…… (10) marks Total ……………………………………………..….……………………...……….…(100) marks 6 SURFACE AND INTERFACIAL TENSION  Interface: is the boundary between 2 phases in contact with each other. Surface: is the boundary between 2 phases, one of them is gas or vapor. 7  Surface Interface No interface between two gases because they mix in all proportions. 8 Surface and interfacial tension: Adhesion force: act between molecules of different phases. Cohesion force: act between molecules of the same phase. Cohesion forces keep the phases separate while adhesion force tends to increase the affinity of two phases. If adhesion forces are stronger miscibility takes place. Molecules at the surface do not have the proper attraction force like in the bulk of liquid or solid. Therefore, the surface of a liquid contract and the molecules at the interface pulled together and this yields the surface tension. ✓ Surface tension: is the force per unit length (dyne/cm) on the surface of a liquid which opposes expansion of the surface area. OR : ✓ Surface tension: is the force per unit length (dyne/cm) that must be applied parallel to the surface so as to counterbalance the net inward pull of molecules of interface together. 9 10  INTERFACIAL TENSION It is present at the interface between two immiscible liquids. 11 Surface and interfacial tension: ✓ Interfacial tension: is the force per unit length existing at the interface between two immiscible liquid phases, and has the unit of dyne/Cm. ✓ Interfacial tensions are less than surface tensions because the adhesive forces between two liquid phases forming an interface are greater than when a liquid and a gas phase exist together (increase adhesive forces cause a decrease in interfacial tension). ✓ If two liquids are completely miscible, no interfacial tension exists between them. ✓ Greater surface tension reflects higher intermolecular force of attraction, thus, increase in hydrogen bonds or molecular weight cause increase in ST ✓ Surface tension is inversely proportion to the temperature, as increasing the temperature will increase the distance between molecules so cohesive force will decrease and surface tension decrease. 12 Potential energy of a molecule on the surface of a liquid is higher than the other molecule inside of the liquid Surface tension: is the work W required to create a unit area of surface is known as SURFACE FREE ENERGY/UNIT AREA (ergs/cm2) erg = dyne. cm W=γ∆A Its equivalent to the surface tension γ Thus the greater the area A of interfacial contact between the phases, the greater the free energy. For equilibrium, the surface free energy of a system must be at a minimum. Thus Liquid droplets tend to assume a spherical shape since a sphere has the smallest surface area per unit volume. 13 Measurement of surface and interfacial tension I- capillary rise method: useful for measuring the surface and not the interfacial tension When a capillary tube is immersed in a liquid like water → the liquid immediately rises up the tube to a certain height. There are two forces opposite to each other: the upward force due to the surface tension against the force due to the liquid weight in the tube. 14  If a capillary tube of inside radius =r immersed in a liquid that wet its surface, the liquid continues to rise in the tube due to the surface tension, until the upward movement is just balanced by the downward force of gravity due to the weight of the liquid The upward component of the force resulting from the surface tension of the liquid at any point on the circumference is given by: γ= F/L F = γ cos Ө * L F = γ cos ϴ * 2 π r Ө = the contact angle between the surface of the liquid and the capillary wall 2 π r = the inside circumference of the capillary. For water the angle Ө is insignificant, i.e. the liquid wets the capillary wall so that cos Ө = unity 2 π r γ = volume*density*g 2 π r γ = π r2 h ρ g γ = 1/2 r h ρ g Cont. angle Cont. angle water and glass Mercury and glass 15 II- drop weight and drop count method: If a liquid is allowed to fall slowly through a capillary tube → the liquid first forms a drop at the tip of the tube which increase in size → finally detaches from the tip when the weight of the drop equals the total surface tension at the border of the tip. W=2 π r γ Where, W=weight of one drop of liquid R=radius of the capillary γ =surface tension of the liquid Surface tension of a liquid is determined by one of these methods using a drop pipette (stalagmometer) 1-drop weight method 2-drop count method 16 1-Drop Weight Method the stalagmometer consists of a glass tube with a bulb. It has two marks A and B one above the bulb and the other below it. There is a capillary at its lower tip. Process: clamp the stalagmometer vertically in the determined liquid. Suck up to the mark A. allow the liquid to drop down. collect 20 or 30 drops in a tarred vessel. The weight of one drop is determined (w). The surface tension is given by the equation w=2 π r γ or γ =w/2 π r We can determine the relative surface tension of a liquid, related to water.  1 m1 =  2 m2 17 2-Drop count method process: as previous method fill the liquid into the stalagmometer to be between A and B marks, the number of drops formed between A ,B are counted and apply the equation γ =vρg/2 π r n v ρ = volume x density= mass of one drop n= number of drops g= gravitational force for determination of relative surface tension of a liquid to water  1 n2 d1 n2 1 Relative surface tension of a liquid = = 2 n1d 2 n1  2 where: ρ1or d1=density of liquid ρ2 or d2= density of water=1 gm/cm3 or gm/ml n1=number of liquid drops n2=number of water drops 18