【正文】 ation rate to 300 μm ? Light energy diffraction or light scattering to 500 μm laser scattering to 2022 μm photon correlation spectrum ? Laser Holography to 100 μm provide information of shape ? Cascade impaction (級聯(lián)撞擊 ) A bination of the above methods and others is often preferred to provide greater assurance of size and shape parameters. 9 Particle size and analysis Stokes’ law/relation ? ? ? ?ηηv 18 gddD9 gdd2r 212212 ????v: velocity of the sedimentation in cm/sec r: particle radius in cm D: particle diameter in cm d1: density of the particle in g/ml d2: density of the liquid in g/ml g=gravitational constant= cmcm1cm1s 1 cp =1 mPa a particle is any unit of matter having defined physical dimensions. Micromeritics includes a number of characteristics including particle size, particle size distribution, particle shape, angle of repose(休止角 ), porosity(空隙率 ), true volume(真實(shí)體積 ), bulk volume(總體積、松容積 ), apparent density(松密度 ) and bulkiness(膨松度 ) . A reduction in a powder’s particle size increases the number of particles and the powder’s total surface area. 11 particle size determined by microscopic method size group of counted particles/μm Middle value μm “d” Number of particles per group “n” “nd” 4060 50 15 750 6080 70 25 1750 80100 90 95 8550 100120 110 140 15400 120140 130 80 10400 ∑n=355 ∑nd=36850 335 536 85 0nndd av ??? ??12 particle size determined by sieving method Seive number Arithmetic mean opening (mm) Weight retained (G) % Retained %Retained Mean opening 20/40 40/60 60/80 80/100 100/120 ? ? ? ? mm 100100s i z e a ve%re t a i ne ddav ???? ?13 Angle of repose（休止角） The angle of repose is a parameter used to estimate the flowability of a powder. h r θ rhta n g e n t θ ?Powders with low angles of repose will flow freely and powders with high angles of repose will flow poorly. A number of factors, including shape and size, determine the flowability of powders. ?Shape: Spherical particles flow better than needles. ?Size: Very fine particles do not flow as freely as large particles. a) 2502022 μm: flow freely if the shape is amenable b) 75250 μm: may flow freely or cause problems, depending on shape and other factors c) less than 100 μm: Flow is problem with most substances. 14 Other characteristics of micromeritics 1 0 0V o i dP o r o s i t y ??bu lkbu lkVVVV oi d ??b u l ka Vs a m pl e t h eofw e i g h t )de n s i t y ( ρa(bǔ) ppa r e n t ?100V VVP oros i t ybu l kbu l k ???Vs a m pl e t h eofw e i g h t )de n s i t y ( ρ t r u et ?a膨松度 ρ1B)bul ki ne s s ( ?15 Comminution(粉碎 ) of drugs Definition Comminution is the process of reducing the particle size of a solid substance to a finer state of subdivisions. It is used to a) facilitate crude drug extraction, b) increase the dissolution rates of a drug, c) aid in the formulation of pharmaceutically acceptable dosage forms, and d) enhance the absorption of drugs. 16 Comminution(粉碎 ) of drugs Mechanism of minution is overing the internal adhering force(內(nèi)聚力 ) with mechanical action including: a) impaction(沖擊力 ) b) pression(壓縮力 ) c) cuttiing/shearing(剪切力 ) d) bending(彎曲力 ) e) rubbing(研磨力 ) 17 Comminution(粉碎 ) of drugs Trituration（研磨） :the process of grinding(磨碎 ) a drug in a mortar to reduce its particle size. Tools: mortar (研缽 ) and pestle (研杵 ) Application: on a small scale On a large scale Tools: ball mills(球磨機(jī) ), colloid mills(膠體磨 ), impact mills(沖擊式粉碎機(jī) ) and fluidenergy mills(流能磨 ) 18 Comminution(粉碎 ) of drugs 19 Comminution(粉碎 ) of drugs 流能磨的優(yōu)點(diǎn)： 能耗低 ； 同時(shí)完成 微粉碎和微粉分選 ； 磨損小 ，由于主要粉碎作用是粒子相互沖擊碰撞，高速粒子與壁面很少碰撞，可 適用粉碎硬度較大的物料 ； 粉碎粒度小，在 d≤5μm； 物料在氣流帶動(dòng)下自身碰撞粉碎，不帶入介質(zhì) ,無污染 。 20 Comminution(粉碎 ) of drugs Levigation（水飛 ,液中研磨） : bining the powder material and a small amount of liquid （ the levigating agent: mineral oil and glycerin） in which the powder is insoluble, then triturating the mixture to reduce the particle size and grittiness of added powders (a paste is produced), this process is termed levigation. Tools: mortar, pestle or an ointment tile Application: the smallscale preparation of ointments 21 Comminution(粉碎 ) of drugs What is ointment tile, and how to use it? It is a flat rectangular or square slab of glass or porcelain. It is also an excellent work surface for triturating and levitating sm