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Published on April 26, 2014

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A Seminar on PARTICAL Characterization.:  APPASAHEB BIRNALE COLLEGE OF PHARMACY, SANGLI. 2012-13 . A Seminar on PARTICAL Characterization. Presented By Guided By Mr. Basavraj S. Ramshetti. Dr. R.R.Shaha M pharm I (Pharmaceutics) HOD Pharmaceutics Dept. 1 Content..: Content. . Introduction. Need Some Equivalent Diameters. Particle Characterization methods . -> Optical microscopy. -> Sieving method. -> Sedimentation. -Anderson pipette. -Photo sedimentation. -> Conductivity method. -> Transmission electron microscopy (TEM) -> Light scattering - Static light scattering (SLS) - Dynamic light scattering (DLS) -> Shape factor. -> XRD Method. -> Gas absorption method. -> Air permeability method. Conclusion. References. 2 Introduction.: Introduction. Particles have some micron in size. So difficulty to characterize size, shape, surface area etc. Several advanced techniques used to characterize these parameters of particle. Spherical particles are easy to express in diameter but not the irregular particles. But particles are irregular in shape, so for expressing it equivalent diameters are used. 3 NEED...: NEED. .. Particle size & surface area influence the release of drug from a dosage form that administered orally, rectally, parenteraly & topically. & also affects- -> Absorption & drug action. -> Physical stability. -> Dose uniformity. So to study these parameters, there is necessary to characterize particle size, shape, surface area etc . 4 SOME EQUIVALENT DIAMETERS..: SOME EQUIVALENT DIAMETERS.. Surface diameter :- Diameter of a sphere having the same surface area as the particle Volume diameter:- Diameter of a sphere having the same volume as the particle. Projected area diameter:- Diameter of the circle having the same area as the projection area of particle. Stoke’s diameter:- Diameter of equivalent sphere having same sedimentation rate of particle. 5 Conti...: Conti... Sieve diameter:- Diameter of sphere that passes through the same sieve as that of particle. Volume-Surface diameter:- Diameter of sphere that has same volume to surface area ratio as that of particle. Martin diameter:- Length of the line that bisect the particle image. Feret diameter:- Distance between two tangents on opposite sides of the particle 6 Particle size determination by-:  Particle size determination by- Optical microscope. Range -0.2 to 100 micron Ultra microscope is used for lower limit . Expressed diameter- Projected area diameter . METHOD- Calibrate eyepiece micro-meter. Prepare suspension of particle in suitable solvent like paraffin oil. Mount & estimate the size of particles with help of eyepiece scale. Repeat it for 625 particles. 7 Sieving method:-:  Sieving method:- Range- 50 to 1500 microns. Expressed diameter- Sieve diameter. METHOD: - Arrange sieve in the order of coarse to fine from top to bottom. Pass particles from top & shake it. It flows due to gravity. Weigh the particles retained in each sieve. Calculate mean of that resp. sieve & is reported as under size Data are analyzed for normal, log-normal, cumulative % frequency distribution curve. Calculate geometric mean weight diameter. 8 Sedimentation method...:  Sedimentation method... Range- 1 to 200 micron. Stoke’s diameter :- d st =√18 η h/( ρ s- ρ 0) gt Use : 1. Formulation & evaluation of suspension emulsion. 2.Molecular weight determination of polymer. Principle:= Rate of settling of particle….. Large > Medium > Small. Hence, study involve sampling during sedimentation at different time interval. 9 Particle consideration:=: Particle consideration:= => suspension should diluted(1-2%). => flow should laminar -> R e > 0.2 Turbulent flow. If larger particle, increase density & viscosity of medium. Method:= Anderson Apparatus . -> It contain 550 ml cylinder & 10 ml two way pipette. lower tip of pipette should 20 cm from surface of suspension. -> prepare 2% suspension & transfer to cylinder, shake place 2 way pipette in it. -> At different time 10 ml sample removed. -> Evaporate sample % weigh as undersize then weight is converted. -> Diameter calculated by Stokes law. 10 Photo-sedimentation.: Photo-sedimentation. Measure photo metrically rate of particle settling. Force causing the particle settling- -> Gravitational force. -> Centrifugal force. Range => 0.01 to300 micron. 11 PowerPoint Presentation: 12 Photo-sedimentation apparatus:= Assumption of STOKE’s equation: Assumption of STOKE’s equation Particle must spherical, smooth & rigid. All particle have same density. Move particles independently, possible only when at low concentration.(1%) Fluid behave as continuum with constant velocity. Independent on any velocity & concentration gradient. 13 Photometric measurement.: Photometric measurement. Measurement of solution absorbance as function of time. di2= ∆Ai/Ki.k.c.b.ni where, ∆Ai= change in absorbance. Ki = absorption coefficient. k = shape factor. c = particle concentration. b = path length. n i = no of particle. d i = particle size. 14 PowerPoint Presentation:  Conductivity Method:= Range=> 0.5 to 500 micron Measured diameter = Volume diameter.(measure particle volume convert it to V d. ) Application .=particle growth in suspension & solution. =dissolution of drug in desired medium. =effect of antibacterial agent on growth of microbs. Principle & Working := -> Particles are suspended in electrolyte solution & is filled in sample cell, that has an orifice. Maintain contact with external environment. -> Two electrodes are placed in solution(inside) & suspension(outside). Constant voltage is applied over the electrode, current is passes. -> When suspended passes through orifice, it displaces its own volume of electrolyte & net result change in electrical resistance. -> Is measured in terms of voltage pulse & is related to volume of particle. -> Voltage is amplified & fed to pulse analyzer which previously calibrated in terms of particle size for different threshold setting. 15 PowerPoint Presentation: Conductivity apparatus:= 16 Transmission Electron microscopy(TEM):=: 17 Transmission Electron microscopy(TEM):= A thin sample is subjected to a beam of electrons. The dark spots on the positive of the detecting film correspond to dense areas in the sample that inhibit electron transmission. These dark spots form the outline of metal particles or crystallites and, hence, their sizes can be determined. Next slide A TEM of sintered Pt, dispersed on TiO 2 (500Å ) PowerPoint Presentation: 18 Light scattering:=:  Light scattering:= Measures - Area diameter or volume diameter. Principle of operation Interaction with laser light the light are scattered and the intensity of the scattered light are measured Two principles; Static light scattering Dynamic light scattering Size range- 0.0001-1000 m Benefits Well established instruments are easy to operate yield highly reproducible data Drawbacks Diluted samples-changes in properties. 19 Static light scattering:=:  Static light scattering:= Particle size information is obtained from intensity of the scattering pattern at various angles. Intensity is dependent on wavelength of the light Scattering angle particle size relative index of refraction n of the particle and the medium. Range= 0.1-2000 micron 20 PowerPoint Presentation: 21 Static light scattering Apparatus:= Light scattering Small and large particles: Light scattering Small and large particles Small particles, one scattering centre < 10 nm Scatter intensity independent of scattering angle. Large particles, multiple scattering centres Scattering depend on angle and gives diffraction pattern 22 Light scattering Mie theory: Light scattering Mie theory The complete solution for homogeneous sphere Incident light of only a single wavelength is considered. No dynamic scattering effects are considered. The scattering particle is isotropic. There is no multiple scattering. All particles are spheres. All particles have the same optical properties. Light energy may be lost to absorption by the particles. Applicable for all sizes Needs to know the refractive index to calculate the size 23 .: . Relay scattering = d < 0.05 λ . Debye scattering = 0.05 λ < d < λ . Mie scattering = d > λ . Mie theory is not applicable for mixture of different components. 24 Continue... Light scattering Fraunhofer theory:=: Light scattering Fraunhofer theory:= Treats that the particle as transparent, spherical adsorbing disc. does not account for light transmitted or refracted by the particle. Diffraction pattern known as ‘Airy pattern.’ x=2 π rs/ λ f . Broader pattern = Smaller particle.& vice-versa. Only applicable to particles much larger than the wavelength of the light Do not need to know the refractive index Much simpler math 25 Dynamic light scattering:=:  Dynamic light scattering:= Range = nano to 5 microns. Measures = Hydrodynamic particle diameter. Particle size is determined by correlating variations in light intensity to the Brownian movement of the particles related to diffusion of the particle. d h = k T/3 π η Dt where, dh= Hydrodynamic particle diameter. k = Boltzmann’s constant . T = Absolute temperature. η = Viscosity of medium. Dt = Transitional diffusion coefficient . 26 . PowerPoint Presentation: 27 Dynamic light scattering Instrumentation. Movement of particle causes fluctuation in pattern.:  Movement of particle causes fluctuation in pattern . The pattern fluctuation Movement is defined by rate of fluctuation. 28 Experimentally the intensity of one speckle is measured. Particle shape:=:  Particle shape:= Particle shape will influence surface area , flow property, packing & compaction property of particle. Sphere has minimum surface area per unit volume. So to decide shape, these property can be compared for sphere & assymetricle particle. α s= π ds2/dp2 α v= π ds3/6dp3 α s=3.124 α v=0.524 shape factor=3.124/o.524 =6 Minimum possible value for shape factor 6 represents sphere . PROPERTY SPHERE PARTICLE Surface area π d s2 α s d p2 Volume (1/6) π ds 3 α v d p3 29 Surface area by:= Absorption method:= :  Surface area by:= Absorption method:= Particle having large specific surface area are good absorbents of gases & solutes from solution. Amount of gas that is absorbed to from a monomolecular layer on the absorbent is function of surface area of the powder. This principle is used to estimate the specific surface. This method is also used to estimate surface diameter. 30 Air permeability method:=: Air permeability method:= PRINCIPLE . Powder packed in sample holder as compact plug. In this packing, surface-surface contacts between particles appear as series of capillary. Surface of these capillary is function of surface area of powder. The air, when allowed to pass, travel through these capillaries so is related to surface area of powder. When air passed through powder bed at constant pressure the bed resist flow of air. These result in pressure drop, greater the surface area per gram of powder, greater the resistance to flow. Permeability of air for given pressure drop is inversely proportional to specific surface. V= A.∆P.t. є / η .Sw2.K.l.(1- є )2 31 PowerPoint Presentation: 32 Air permeability X-Ray Diffraction(XRD):=: X-Ray Diffraction(XRD):= USED TO : 1) characterize – crystallographic structure crystallite size 2) preferred orientation in polycrystalline or powdered solid samples. 3) to identify unknown substances (comparing diffraction data against a database maintained by the International Centre for Diffraction Data). 4) provide structural information of unknown particle. 5) for determining strains in crystalline materials. n λ =2d.sin Φ 33 Conclusion: Conclusion Techniques like microscopy & sieving these have several drawbacks. -> No accuracy. -> Reproducibility. -> Range limit. To overcome these, using advanced technique. TEM, DLS, LS, XRD photo- sedimentation etc. 34 References..: References.. ‘Text book of physical pharmacy’ by Subrhamanyam. Micromeritics. A. Martin, J. Swarbrick & A. Cammarata, physical pharmacy. IIIrd edition. Kaye B. H.: A Random Walk Through Fractal Dimensions (second edition). VCH, Weinheim 1994. Biophysical Measurement (Physics 173) - UCSD - Spring 2002 Bernhard Englitz . Lerk C. F., Bolhuis G. K., Smedema S. S. Interaction of lubricants and colloidal silica during mixing with excipients. Pharm. Acta Helv. 1977;52:33–39. . Bos C. E., Bolhuis G. K., Doorne H., Lerk C. F. Native starch in tablet formulations: properties on compaction. Pharm. Weekbl. Sci. Ed. 1987;9:274–282. 35 THANK YOU….: THANK YOU…. 36

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