1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationColloidal systems Methods for zetapotential determinationPart 2: Optical methodsBS ISO 13099-2:2012National forewordThis British Standard is the UK implementation of ISO 13099-2:
2、2012.The UK participation in its preparation was entrusted to Technical CommitteeLBI/37, Particle characterization including sieving.A list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purport to include all the necessary provis
3、ions of a contract. Users are responsible for its correct application. The British Standards Institution 2012Published by BSI Standards Limited 2012 ISBN 978 0 580 70477 2 ICS 19.120Compliance with a British Standard cannot confer immunity from legal obligations.This British Standard was published u
4、nder the authority of the Standards Policy and Strategy Committee on 31 July 2012.Amendments issued since publicationDate Text affectedBRITISH STANDARDBS ISO 13099-2:2012 ISO 2012Colloidal systems Methods for zeta-potential determination Part 2: Optical methodsSystmes collodaux Mthodes de dterminati
5、on du potentiel zta Partie 2: Mthodes optiquesINTERNATIONAL STANDARDISO13099-2First edition2012-06-15Reference numberISO 13099-2:2012(E)BS ISO 13099-2:2012ISO 13099-2:2012(E)ii ISO 2012 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2012All rights reserved. Unless otherwise specified, no part o
6、f this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCase postale 56 CH-
7、1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in SwitzerlandBS ISO 13099-2:2012ISO 13099-2:2012(E) ISO 2012 All rights reserved iiiContents PageForeword ivIntroduction v1 Scope 12 Normative references . 13 Terms, definitions and symbols 13.1
8、 Terms and definitions . 13.2 Symbols . 24 Principles . 35 Microscopic methods . 46 Electrophoretic light-scattering (ELS) method 56.1 General . 56.2 Cell design . 56.3 Reference beam optical arrangement 66.4 Cross-beam optical arrangement . 66.5 Signal processing . 76.6 Determination of electrophor
9、etic mobility 97 Calculation of zeta-potential . 98 Operational procedures .108.1 Requirements .108.2 Verification 128.3 Sources of measurement error 138.4 Test report .15Annex A (informative) Electroosmosis within capillary cells .16Bibliography .19BS ISO 13099-2:2012ISO 13099-2:2012(E)ForewordISO
10、(the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical comm
11、ittee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrote
12、chnical standardization.International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member
13、 bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying
14、any or all such patent rights.ISO 13099 was prepared by Technical Committee ISO/TC 24, Particle characterization including sieving, Subcommittee SC 4, Particle characterization.ISO 13099 consists of the following parts, under the general title Colloidal systems Methods for zeta-potential determinati
15、on: Part 1: Electroacoustic and electrokinetic phenomena Part 2: Optical methodsThe following part is under preparation Part 3: Acoustic methodsiv ISO 2012 All rights reservedBS ISO 13099-2:2012ISO 13099-2:2012(E)IntroductionZeta-potential is a parameter that can be used to predict the long term sta
16、bility of suspensions and emulsions and to study surface morphology and adsorption on particles and other surfaces in contact with a liquid. Zeta-potential is not a directly measurable parameter. It can be determined using appropriate theoretical models from experimentally determined parameters, suc
17、h as electrophoretic mobility. Optical methods, especially electrophoretic light scattering, have been widely used to determine electrophoretic mobility of particles or macromolecules in suspension or in solution. The purpose of this part of ISO 13099 is to provide methods for measuring electrophore
18、tic mobility using optical means and for calculating zeta-potential. ISO 2012 All rights reserved vBS ISO 13099-2:2012Colloidal systems Methods for zeta-potential determination Part 2: Optical methodsIMPORTANT This part of ISO 13099 shall be read in conjunction with ISO 13099-1, which gives a compre
19、hensive overview of the theory.1 ScopeThis part of ISO 13099 specifies two methods of measurement of electrophoretic mobility of particles suspended in a liquid: video microscopy and electrophoretic light-scattering. Estimation of surface charge and determination of zeta-potential can be achieved fr
20、om measured electrophoretic mobility using proper theoretical models, which are described in detail in ISO 13099-1.2 Normative referencesThe following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated refere
21、nces, the latest edition of the referenced document (including any amendments) applies.ISO 13099-1, Colloidal systems Methods for zeta-potential determination Part 1: Electroacoustic and electrokinetic phenomenaISO Guide 30: Terms and definitions used in connection with reference materials3 Terms, d
22、efinitions and symbols3.1 Terms and definitionsFor the purposes of this document, the following terms and definitions apply.3.1.1Brownian motionrandom movement of particles suspended in a liquid cause by thermal movement of medium molecules3.1.2Doppler shiftchange in frequency and wavelength of a wa
23、ve for an observer moving relative to the source of the wave3.1.3electric surface potentialdifference in electric potential between the surface and the bulk liquidNOTE Electric surface potential is expressed in volts.INTERNATIONAL STANDARD ISO 13099-2:2012(E) ISO 2012 All rights reserved 1BS ISO 130
24、99-2:2012ISO 13099-2:2012(E)3.1.4electrokinetic potentialzeta-potential-potentialdifference in electric potential between that at the slipping plane and that of the bulk liquidNOTE Electrokinetic potential is expressed in volts.3.1.5electroosmosismotion of liquid through or past a charged surface, e
25、.g. an immobilized set of particles, a porous plug, a capillary or a membrane, in response to an applied electric field, which is the result of the force exerted by the applied field on the countercharge ions in the liquid3.1.6electroosmotic velocityeouniform velocity of the liquid far from the char
26、ged interfaceNOTE Electroosmotic velocity is expressed in metres per second.3.1.7electrophoretic mobilityelectrophoretic velocity per electric field strengthNOTE 1 Electrophoretic mobility is positive if the particles move toward lower potential (negative electrode) and negative in the opposite case
27、.NOTE 2 Electrophoretic mobility is expressed in metres squared per volt second.3.1.8electrophoretic velocityeparticle velocity during electrophoresisNOTE Electrophoretic velocity is expressed in metres per second.3.1.9slipping planeshear planeabstract plane in the vicinity of the liquid/solid inter
28、face where liquid starts to slide relative to the surface under influence of a shear stress3.2 Symbolsa particle radiusD diffusion coefficientE electric field strengthkBBoltzmann constantI light intensityNAAvogadros numbern medium refractive indexRcapcapillary radius2 ISO 2012 All rights reservedBS
29、ISO 13099-2:2012ISO 13099-2:2012(E)S() frequency power spectrum of scattering characteristic Lorentzian half peak width medium permittivity electrokinetic potential (zeta-potential)0medium viscosity angle between incident light and scattered light angle between two cross-beams reciprocal Debye lengt
30、h wavelength electrophoretic mobilityeoelectroosmotic mobility of liquid frequency angle between scattered light and electric field direction delay time in autocorrelation function volume fraction rotational frequency (= 2)4 PrinciplesA suspension of particles having a given electrokinetic charge is
31、 placed in a cell which has a pair of electrodes placed some distance apart (Figure 1). This cell can be in the form of either a cylindrical or rectangular capillary with electrodes at either end, or a pair of electrodes at a known fixed distance apart that are dipped into a cuvette or other vessel.
32、 A potential is applied between the electrodes. Due to the process of electrophoresis, particles carrying a net negative charge are drawn towards the electrode of opposite sign and vice versa. In addition, if the capillary walls are charged, then an effect called electroosmosis causes the liquid to
33、stream along the capillary walls. The direction and velocity of this flow depends on the sign and magnitude of the wall charge. The resulting velocity of the particle in the frame of references associated with the cell is superposition of the electrophoretic velocity and the velocity of electroosmot
34、ic flow. Here it should be noted that the time taken for the particle to reach the terminal electrophoretic velocity after the application of the electric field is much shorter than the period of time needed to fully establish the electroosmosis flow throughout the whole cell. This difference is exp
35、loited in some implementations. The velocity of the particles measured at a specific position can be determined using either video microscope or electrophoretic light scattering through a laser Doppler arrangement. Both the velocity and the direction of the moving particles in the frame of reference
36、s associated with the cell are determined. Provided that the distance between the electrodes is known together with the applied electric potential, then the electrophoretic mobility can be established, from which a zeta-potential can be calculated using established theories. Alternatively, calibrati
37、on with particles having a known zeta-potential can be used to eliminate the need to determine the unknown cell constant of a particular cell.There are two distinctively different approaches to monitor particle motion in the electric field. Historically, the first deals with particle images observed
38、 through a microscope. It is referred to as the “microscopic method”, or alternatively as “microelectrophoresis”. The second relies on measuring light scattered by particles and extracting information on electrophoretic mobility from the Doppler frequency shift of the scattered light. This method is
39、 called the “electrophoretic light-scattering method”. For optical techniques, a cell constant for many types of cells has to be determined, through either calculation or measurement of a solution of known conductivity. ISO 2012 All rights reserved 3BS ISO 13099-2:2012ISO 13099-2:2012(E)daKeyd dista
40、nceaMeasurement zone.Figure 1 Schematic diagram of electrophoresis measurement5 Microscopic methodsThe main principles of these methods can be traced back over two centuries (Reference 1) following the development of microelectrophoresis. A light source illuminates particles migrating under the infl
41、uence of a d.c. or a.c. electric field. The illuminated particles can be observed due to scattering. This illumination can be arranged either as a bright field or as a dark field or both (Reference 2). The contrast afforded by the bright field illumination is inadequate to illuminate particles with
42、sizes smaller than about 0,2 m. Dark field illumination is suitable for capturing images of moving nano-particles with sizes down to nanometre scale.There are several approaches to the treatment of microscopic images of the moving particles. Depending on the degree of operator involvement, it can be
43、 classified as manual, semi-automatic and automatic. Manual methods track the movement of one or several individual particles by eye and a stopwatch and therefore are typically time consuming, tedious to employ and inaccurate.In the semi-automatic methods, particles are tracked through a microscope
44、manually while the apparatus either scans the illuminating light or moves a prism reflecting the illuminated image of particles. When the light-scanning velocity or prism-moving velocity is semi-automatically adjusted so that the particle image as viewed in the microscope is static, such a velocity
45、is the electrophoretic velocity of particles (References 34). These methods are only applicable to samples having a homogeneous electrophoretic mobility.There are designs combining the manual microscopic observation with automatic electrophoretic light-scattering signal analysis to measure samples o
46、f polydisperse electrophoretic mobility (References 56).The appearance of modern charge-coupled devices (CCD) and computers has made it possible to capture images, transfer the images sequentially to a computer, and then using sophisticated image analysis to reconstruct trajectories of particles mov
47、ing under the influence of an electric field from the time-stamped video frames. Only particles confined to video visibility can be measured. In order to record accurate moving distances, from the time duration between frames and the distance each particle moved, the velocity of each particle is cal
48、culated and combined with the applied field strength, and its electrophoretic mobility is obtained. Dark field illumination extends this method to nano-particles. This method allows application of electric field for very short periods of time, which resolves the problems of thermal convection and el
49、ectrochemical contamination. Concentration of particles shall be very low in order to track individual particles.A 90 laser scattering device is a typical optical arrangement of modern instruments. The laser serves as the illumination of the microscope focal plane. Both laser beam and microscope axis are perpendicular to the electric field. In Figure 2, the field direction is perpendicular to the plane of the drawing. Laser illumination and microscope require alignment with the stationa
