laPart iclesize analys is-Laserdiffra ction method s(ISO-13320-1)Introd uctio nLaser diffra ction method s are nowada ys widely used for partic le sizing in many differ ent applic ation s. The succes s of the techni que is based on the tact that it can be applie d to variou s kindsof partic ulate system s, is fast and can be automa ted and that a variet y of commer cialinstru ments i s availa ble. Nevert heles s, the proper use of the instru mentand the interp retat i on of the result s requir e the necess ary cautio n.Theref ore, there i s a need for establi shin g an intern ation al standa r d for partic l e size analysi s by laserdiffra ction method s. Its purpose i s to provid e a method ol ogy for adequa te qualit y contro l in partic l e size analysis.Histor icall y, the laserdiffra ction techni que starte d by taking only scatte ri ng at small angles into consid erati on and, thus, has been knownby the followi ng names:-fraunh oferdiffra cti on;-(near-) forwar d lightscatte ring;-low-angle l aser light scatte ring (LALLS).Howeve r, the techni que has been broade ned to include lightscattering in a wider angula r range and applic a tion of the Mie theory in addition to approx i mati ng theori es such as Fraunh ofer and anomal ous diffraction.The laserd iffra ction techni que is basedon the phenom enon that particles scatte r light in all direct i ons with an intensity patter n that is dependent on partic l e size. All presen t instru ments assume a spheri cal shape f or the partic l e. Figure1 illust rates the charac teris ticsof single partic lescatte ringpatter ns: altern ation of high and low intens ities, with patter ns that extend for smalle r partic les to wider angles than for larger particles[2-7,10,15 in the biblio g raph y].Within certai n limits the scatte ri ng patter n of an ensembl e of particles is identi cal to the sum of the indivi dualscatte ringpatter n s of all partic les presen t. By using an optica l model to comput e scatte ring f or unit volume s of partic l es in select ed size classe s and a mathem atica l deconvoluti on proced ure, a volume tricpartic le size distri butio n is calcul ated, the scatte ringpatter n of which fits best with the measur e d patter n (see also annex A).A typica l diffra ction instru m entconsis t s of a lightbeam (usuall y a laser), a partic ulate disper singdevice, a detect or for measuri ng the scatteringpatter n and a comput er for both contro l of the instru ment and calculation of the partic l e size distri butio n. Note that the laserdiffra ction technique cannot di stin gui sh betwee n scatte ri ngby single partic l es and scatteringby cluste r s of primar y partic l es formin g an agglom erate or an aggreg ate. Usuall y, the resulti ng partic l e size for agglom erate s is relate d to the cluste r size, but someti mes the size of the primar y partic l es is reflected in the partic l e size distri butio n as well. As most partic ulate sample s contai n agglom erate s or aggreg ates and one is genera lly intere sted in the size distri butio n of the primar y partic l es, the cluste r s are usuall y dispersed into primar y partic l es before measur ement.Histor i call y, instru ments only used scatte ring angles smalle r than 14°,which limite d the applic a tion to a lower size of about 1μm. The reason for this limita ti on i s that smalle r partic l es show most of theirdistinctive scatte ring at larger angles (see also annex Z).Many recent instruments allow measur ement at larger scatte ri ng angles, some up to about150°,for exampl e throug h applic a ti on of a conver ging beam, more or larger lenses, a second laserbeam or more detect ors. Thus smalle r particles down to about 0.1μm can be sized. Some instru ments i ncorp orate additi onal i nform ati on from scatte ring i ntensities and intensity differ ences at variou s wavele ngths and polari zatio n planes in order to improv e the charac teriz ati on of partic l e sizes in the submic r ometre range.Partic l e size analysis – Laser diffra ction m ethod s-Part 1:Genera l princi ples1 scopeThis part of ISO 13320provid e s guidan ce on the measur ement of size distri butio n s of partic l es in any two-phase system, for exampl e powder s, sprays, aerosol s, suspen si ons, emulsi ons and gas bubble s in liquid s, throug h analysi s of their angula r lightscatte ring patter ns. It does not addres s the specif i c requir ement s of partic le size measur ement of specif i c produc t s. This part of ISO13320 is applic a ble t o partic l e sizesrangin g from approx i mate ly 0.1μm to 3μm.For non-spheri cal partic l es, an equiva lent-sphere size distri butio n is obtain e d becaus e the techni que uses the assump tionof spheri cal partic l es in its optica l model. The resulti ng partic l e size distri butio n may be different from thoseobtain e d by method s basedon otherphysic al princi ples(e.g. Sedime ntati on, sievin g).3,terms, defini tions and symbol sFor the purpos es of this part of ISO 13320, the follow ing terms, defini ti ons and symbol s apply.3.1 terms, defini ti ons3.1.1 absorp ti onintrodu ctio n of intensi ty of a lightbeam traver singa medium throug h energy conver si on i n the medium3.1.2 coeffi cient of variati on (变异系数)Noativ e measur e(%) for precis i on: standa rd deviat ion divide d by mean value of popula ti on and multip l ied by 100 or normal di stri butio n s of data the median is equal t o the mean3.1.3compl ex refrac tive i ndex（Ｎｐ）Refrac tive i ndexof a partic l e, consis tingof a real and an imagin ary (absorp tion) part.Np=n p-ik p3.1.4 relati ve refractive index（m）comple x refrac tive i ndexof a partic l e, relati ve to that the medium。
