粒度表征及激光粒度分析技術進展

1、 Mar. 31, 2004, Mar. 31, 2004, 顆粒特性分析測定儀器顆粒特性分析測定儀器n英國馬爾文公司英國馬爾文公司n激光衍射粒度分析儀激光衍射粒度分析儀 0.02 3500 微米 500/1000 Hz 掃描速率n激光動態(tài)光散射分析儀激光動態(tài)光散射分析儀 1 5000納米/ZETA電位n干粉干粉/噴霧粒度分析儀噴霧粒度分析儀n在線粒度分析儀在線粒度分析儀n高濃度超聲粒度分析儀高濃度超聲粒度分析儀n絕對分子量分布測定儀絕對分子量分布測定儀 100 1 e 12 Daltonsn美國康塔公司美國康塔公司n全自動比表面及孔隙度分析儀全自動比表面及孔隙度分析儀 (分析站數(shù)可選 1/2

2、/3/6) 0.005 m2/g 3.5 5000 埃n壓汞儀壓汞儀 3.6納米 426 微米孔徑n化學吸附儀化學吸附儀 (TPR/TPD)n流動法快速比表面測定儀流動法快速比表面測定儀n全自動真密度計全自動真密度計n自動堆密度分析儀自動堆密度分析儀Malvern Instruments UK Headquarters 英國馬爾文儀器有限公司英國馬爾文儀器有限公司 _激光粒度分析儀的創(chuàng)始人激光粒度分析儀的創(chuàng)始人- - 世界上最大的激光粒度分析儀專業(yè)設計和生產(chǎn)廠家世界上最大的激光粒度分析儀專業(yè)設計和生產(chǎn)廠家- - 世界上第一臺相關處理器世界上第一臺相關處理器- - 世界上第一臺激光衍射法粒度分析

3、儀，世界上第一臺激光衍射法粒度分析儀，- - 世界上第一臺激光世界上第一臺激光PCSPCS粒度分析儀粒度分析儀- - 世界上第一臺超聲粒度分析儀世界上第一臺超聲粒度分析儀- - 銷售量占世界第一，僅中國大陸已有銷售量占世界第一，僅中國大陸已有450450臺以上臺以上- - 已獲得已獲得ISO9001ISO9001標準標準, , 歐洲歐洲EMCEMC標準認證標準認證, GMP, GMP標準認標準認 證，唯一完全符合美國證，唯一完全符合美國FDA QSpecFDA QSpec要求要求- - 多方位應用支持，在中國設立正式技術服務中心多方位應用支持，在中國設立正式技術服務中心. .First .19

4、77- IEE McRobert Award1977- Queens Award for Technical Achievement1981- Queens Award for Export Achievement1987- TASC Award for Analytical Equipment1988- Queens Award for Technical Achievement1988- Queens Award for Export Achievement1993- Engineering Safe Workers Award1994- British Safety Council Aw

5、ard and?.誰關心粒度分布？石油石化、材料科學、化工、制藥、地質、涂料和顏料、陶瓷、磨料、造紙、電池、能源和航空，稀土，非礦，航天，軍工墨粉，食品，環(huán)保（水處理和沙塵）等領域 Malvern End User Field Distributionin 2000 (* new gain point)4%18%13%17%10%2%4%8%4%4%4%2%8%2%Pharm.*Inst./Univ.Petro./Chem*Chem.(Coat,dye.)*Geo./Soil/sand*Cement*Electronics/BatteryPowder/Mineral*Non-Fe MatalC

6、eramicsAerospace*Coal Slurry*Alumina Factory*Cosmetic激光粒度儀在輕工行業(yè)的應用n食品、醫(yī)藥工業(yè)：新型天然高吸收率食品、飲料、藥品或保健品n1）動物超細粉:超細鱉粉、蛇粉、螞蟻粉、蛆粉等等。n2）植物超細粉：植物奶、蔬菜汁（粉）、果汁或粉、天然植物色素等等。n3) 超細藥物：藥物超細后，可提高吸收率和療效；中藥材超細后，不僅可提高吸收率和療效，而且還是服用方便，避免傳統(tǒng)復雜的飲片煎煮。n4) 其他：超細麩皮粉、玉米胚芽渣粉、甘蔗渣粉、粉茶、靈芝粉、花粉、螺旋藻粉、人參粉等等。激光粒度儀在輕工行業(yè)的應用n 紡織工業(yè)：n加入超細氧化硅、氧化鈦可以

7、提高產(chǎn)品的質量和光潔度；n利用納米氧化鋅吸收紫外線的能力，制成防紫外線服裝化纖；n利用納米氧化鋅對遠紅外發(fā)射性能，制成內衣、護腰、護腕，可以改善血液循環(huán)和組織供氧能力，加強機體水分子共振，促進新陳代謝，從而起到輔助理療保健功效；也可利用其抑菌、殺菌作用制成抗菌纖維。n皮革：超細蠶絲的加入可制出高性能、高光潔度的皮革。n化妝品和日用品：n超細鈦白粉、碳酸鈣、蠶絲和色素等是口紅、粉餅、護膚膏、肥皂、牙膏、洗發(fā)液的重要組成原料。另外，利用納米TiO2吸收紫外線的能力，可制成防曬劑、抗菌劑等。激光粒度儀在輕工行業(yè)的應用n油漆、涂料：n加入超細粉后，可制成高性能、高附著力的新型產(chǎn)品；加入TiO2達到抗菌

8、、消臭的目的；加入超微粉體香味劑制成自然香型涂料。n造紙、橡膠、塑料等工業(yè)：n加入固體填料如重質碳酸鈣、氧化鈦、氧化硅等超細粉后，可制成高性能銅板紙、塑料及橡膠制品；納米陶瓷粉與高分子材料復合可顯著的提高工程塑料的力學性能。n抗菌防臭的餐具、衛(wèi)生潔具，包裝材料等等。n其他：超細碳黑可制成高質量的復印或打印粉墨。 激光粒度儀在乳品及相關行業(yè)的應用 粒度與食品色澤、口感、穩(wěn)定性密切相關n脫脂奶及奶制品的穩(wěn)定性：光明乳業(yè)n植物油脫色：白土n香精香料等原料：蘇州丹尼斯克，國際香精香料公司n巧克力：可可粉和蔗糖粒度作為品質及口感的指標： 確保巧克力只溶在口：Cadbury Ltd.n高品質奶油、冰激淋、

9、人造黃油和低脂黃油片需要粒度控制：Unilever 。n環(huán)境保護：水質監(jiān)測和廢水處理：粒度和zeta電位n面粉粒度控制：機械化生產(chǎn)面條及其他面食所必需。Story.Story.來自一個懊悔者的傾訴來自一個懊悔者的傾訴- 2002- 2002年年3 3月月1919日日面粉烏冬面還需要粒度控制？No￥3000萬投資萬投資60車皮廢品車皮廢品 ！ 粉體顆粒粒度是產(chǎn)品的主要質量指標，它可用來預測產(chǎn)品穩(wěn)定性、紙張涂層特性、顏料覆蓋能力、水泥凝固時間、藥物活性，食品色澤及口感等等，也是選擇分離設備，預測濾餅層的滲透性或比阻等的依據(jù)。 粉體顆粒粒度在各個環(huán)節(jié)的實時監(jiān)控是現(xiàn)代化生產(chǎn)的重要手段。為什么他們關心粒

10、度分布？為什么他們關心粒度分布？粒度分布控制有什么意義？由粗放型向集約型經(jīng)營轉變的必備手段（1）晶粒：晶粒：指單晶顆粒，即顆粒內為單相，無晶界。（2）一次顆粒：一次顆粒：指含有低孔隙率的一種獨立的粒子。它能被電子顯微鏡觀察到。（3）團聚體：團聚體：是由一次顆粒為降低表面勢能而通過范德華力或固定的橋鍵作用形成的更大顆粒。團聚體內含有相互連接的孔隙網(wǎng)絡，它能被電子顯微鏡觀察到。（4）二次顆粒：二次顆粒：指人為制造的粉料團聚粒子。 目前所謂“納米材料”的功能絕大多數(shù)體現(xiàn)為 團聚體的功能，其粒度能被馬爾文激光粒度儀 精確測出。若能將團聚體分散成一次顆粒，則 將表現(xiàn)出納米顆粒更多的特性。 關于顆粒的基本

11、概念關于顆粒的基本概念n什么是顆粒？什么是顆粒？nFeret 直徑 - 平行切面之間的距離. nMartin 直徑 - 等分線直徑n最長直徑n最短直徑n等效周長直徑 - 同等周長的圓圈直徑n等效投影面積直徑 - 與投影面積相同的圓面直徑n等效表面積直徑n等效體積直徑各種方法對球體粒徑平均值的不同表征各種方法對球體粒徑平均值的不同表征對于三個直徑分別為1、2、3單位的球體，它們的平均值是多少呢？n電子顯微鏡法：取長度平均值 D1，0 平均直徑=（1+2+3）/3 = 2.00 =d/nn 圖像分析儀： 取面積平均值 D2，0 平均直徑=Sq. rt. (12+22+32)/3 = 2.16 =

12、Sq. rt.(d2/n)n 電場感應法： 取顆粒的體積平均值 D3，0 平均直徑=Cube rt. (13+23+43)/3 = 2.20 = Cube rt.(d3/n)n激光衍射法： 取平均當量體積值 D4，3，因為它不需要顆粒數(shù) 如果顆粒的密度不變，這個值與平均當量重量值是一致的。 D4,3 = (14+24+34)/(13+23+33) = 2.72 =d4/ d3 D3,2 = (13+23+33)/(12+22+32) = 2.57 = d3/d2 D3，2稱作當量面積平均值，或稱作索爾特平均直徑（SMD）， 它通常應用于顆粒的表面活性或表面積顯得非常重要的領域（如 催化作用或燃

13、燒作用）。 哪種表征或結果是哪種表征或結果是“正確正確”的？的？都正確，都反映了顆粒的某種特性即使是球體，不同的方法也給出不同的平均值在描述粒徑大小時，必須同時指明測定方法才有意義不同粒度測定方法之間的比較沒有意義不同方法之間的比較必須轉化成 同一粒徑的定義 常見粒度分析方法統(tǒng)計方法代表性強, 動態(tài)范圍寬分辨率低n篩分方法 38微米- n沉降方法0.01-300微米n光學方法0.001-3500微米非統(tǒng)計方法分辨率高代表性差, 動態(tài)范圍窄n顯微鏡方法重復性差光學 1微米-電子0.001微米-n電域敏感法0.5-1200微米優(yōu)點n統(tǒng)計量大, 代表性強n便宜n重量分布缺點n下限38微米n人為因素影

14、響大n重復性差n非規(guī)則形狀粒子誤差n速度慢顯微鏡方法優(yōu)點n可直接觀察粒子形狀n可直接觀察粒子是否團聚n光學顯微鏡便宜缺點n代表性差n重復性差n測量投影面積直徑n速度慢stsfugd218沉降法優(yōu)點n測量重量分布n代表性強n經(jīng)典理論, 不 同 廠 家儀器結果對比性好n價格比激光衍射法便宜缺點n對于小粒子測試速度慢, 重復性差n非球型粒子誤差大n不適應于混合物料n動態(tài)范圍比激光衍射法窄光學方法n激光衍射方法( 0.02-3500微米)nPCS 光子相關光譜方法( 0.001-3微米)n光阻方法(0.01-250微米) 英國馬爾文儀器公司英國馬爾文儀器公司 世界最大的專業(yè)設計及制造廠家世界最大的專業(yè)

15、設計及制造廠家 Small particles scatter light at wide anglesLaserParticlesDetectorFourierLensBeamLarge particles scatter light at narrow anglesParticle CharacterizationTypical Elements of InstrumentsBeamLaser Fourier LensParticle SampleChamber Detector ArraySample Particles Light Scattered from Particles Me

16、asured Scattered Light Intensity Profile0 .3 /3 /3 0 /3 0 0角 度散射光強粒子直徑減少粒子直徑減少10倍，散射光強減弱一百萬倍倍，散射光強減弱一百萬倍 !根據(jù)瑞利散射定律：根據(jù)瑞利散射定律： I D6 / 4 散射光強 粒子直徑 光源波長HeNeLaser2mw Power0. 63 m wavel engt hSpat i alFi l t erPar t i cl essuspendedi nGasorl i qui dFour i erTr ansf or mLensUnscat t er edLi ghtScat t er ed

17、Li ghtMul t iEl ementDet ect orObscur at i onDet ect or技術難點：檢測器面積有限；小粒子散射光弱；雜散光影響選擇哪類激光光源？選擇哪類激光光源？氦-氖氣體激光器(633nm):無背景噪音，對0.3nm顆粒響應 兩類激光器的差異氦氖激光器：n 光源穩(wěn)定性好n 單色性好n 相位一致固體二極管激光器：n 光源穩(wěn)定性差n 分散性高n 相位相關性差，導致數(shù)據(jù)的重復性低Mastersizer 2000 blue light enhancement檢檢 測測 器器 系系 統(tǒng)統(tǒng)nThe first Malvern systems developed mor

18、e than 20 years ago featured a detector design shown herenThis comprised 32 concentric photodiode rings.Live detector elementsInsulating spacesParticle CharacterizationTypical Elements of InstrumentsBeamLaser Fourier LensParticle SampleChamber Detector ArraySample Particles Light Scattered from Part

19、icles Measured Scattered Light Intensity ProfileDetector DesignIn the new design, not only was the dead space completelyeliminated, but the detector dimensions were changedenabling us to measure a much greater angular range, and hence a wider size distribution.Low Angle Laser Light ScatteringThe Com

20、plete no Compromise SolutionParticles in Liquid suspension 0.05-900 micronsReverse Fourier modeExtra Large Angle DetectorsSample cellMain Detector Backscatter detectorConcentrationDetectorMastersizer 2000 光路設計 1998年10月問世FA: 前傾角檢測器； LA: 大角檢測器； BS: 背散射光檢測器Mastersizer 2000有哪些性能突破有哪些性能突破?- - 動態(tài)測定范圍加寬:0.

21、02-2000微米（一次完成）- 粒度分布的分辨率提高，特別是在亞微米區(qū)- 準確性達 1%; 重復性達0.5%- 掃描速度達1000次/秒; 一次測量僅需2秒- 高度智能化,不需更換鏡頭，沒有兩種測試混合-“插拔式”: 分散器快速更換- SOP 操作: ISO 標準化要求- 開放式軟件設計及數(shù)據(jù)庫: 無需用戶編程Carbon black ink.在0.03um 的碳黑樣品中逐步加入100um的透明玻璃球，結果顯示：- 不會對碳黑樣品測量造成影響大慶濾后水中顆粒分布測定（靈敏度實驗：顆粒濃度：4ppm,遮光度=1）趨 勢 圖2 3 4 5 6 記 錄 編號135791113151719Param

22、eterd (0.1)d (0.5)d (0.9)Mastersizer 2000噴射式干法測定噴射式干法測定釹鐵硼粒度分布釹鐵硼粒度分布 5次結果粒度分布趨勢變化分析次結果粒度分布趨勢變化分析釹鐵硼：濕法制備釹鐵硼：濕法制備 費氏粒度費氏粒度=4.7um MS2000激光粒度分析結果激光粒度分析結果: D(3,2)=4.9umContinuous SprayTimeConcentrationSizespray1.xlcNasal Spray FIG 3Latex MeasurementsParticle Diameter (m.)%0 10 20 30 40 50 60 70 80 010

23、20 30 40 50 60 70 80 90 100 0.1 1.0 10.0 100.01000.0496nm Latex-32.019um Latex-39.870um Latex-431.1um Latex-3301um Latex-3100um Latex-7Latex Mixture( single measurement)Particle Diameter (m.)%0 10 20 010 20 30 40 50 60 70 80 90 100 0.1 1.0 10.0 100.01000.0.25/2/9.9/31/100/301-11與跟蹤發(fā)展起來的同類產(chǎn)品相比-馬爾文激光粒

24、度分析儀具有以下特點： 1. 30秒內完成從加樣到打印全部操作，一次得到全范圍粒度 分布圖（例如，0.02 2000微米）。n2. 全范圍統(tǒng)一的激光衍射法，保證背景一致，不會漏檢，無假峰。n3. 速度快，重現(xiàn)性高。每次測試可在1秒鐘內達到500次掃描，重現(xiàn)性優(yōu)于0.5%，在線分析可達每秒2000次掃描。n4. 動態(tài)范圍寬，可以達到20000.02微米或35004微米一個量程。n5. 直接測量體積分布，無需標定，無需校準，無需人工調整。n6. 可有多種分散方式，可進行干法和噴霧測量。n7. 濕法測量可直接用自來水，無需使用超純水(納米粒子除外)。n8. 適用于非球形和混合物料粒子測試。n9. 新

25、型Mastersizer2000具有高度智能化及標準化SOP操作特點， 1m下分辨率極高。n10. 全中文操作及說明應用軟件，MS2000中文操作說明書 The Mastersizer Family馬爾文光子相關光譜儀馬爾文光子相關光譜儀- Zetasizer (HS) 系列: 2 3000 nm- Autosizer 4800: 1- 5000 nmSize distribution(s)51050 1005001000Diameter (nm)510% in classZave = 3.6nmZetasizer系列 納米粒度及Zeta電位分析儀和MPT-1 自動滴定系統(tǒng)The MPT-1

26、是為是為Zetasizer分析儀特制的高效專用自動滴定裝置分析儀特制的高效專用自動滴定裝置 粒徑范圍：2 nm 3000 nm 專利高靈敏測量系統(tǒng),下限測量無須高功率激光器。 2000年最新M3專利技術，具有高分辨高準確性，可分辨混合粒子1mV的Zeta電位差異。 突出的高重現(xiàn)性，由精確的內部溫控技術和在線pH測量加以保證。 全自動三元滴定系統(tǒng)：精確控制、實時測量pH，鹽濃度和電導率的連續(xù)變化。 全自動結果自診斷系統(tǒng)：結果判斷因子(RQF) 保證了每次測量質量。 內置ISO13321標準指導操作。PHOTONCORRELATION SPECTROSCOPYPCSWHAT DOES IT STA

27、ND FOR?PCSWHAT DOES IT DO?It measures the size of small particlesHOW SMALL?VERYSMALL!HOW SMALL IS SMALL?The smallest sized particle we can measure with PCS is 2 nanometres (nm)What is a nanometre?It is 10-7 of a centimetre5 million!How many 2nm particles will fit end to end into 1 cm?02143Lets consi

28、der a rulerSOME PARTICLE SIZES.nRed Blood Cell.7000nmnBacteria/Yeast Cells.2000-3000nmnSmallest particle seen through a light microscope.200nmnViruses10-100nmnMad Cow Disease Prions.10-20nmnProtein (lysozyme).3nmWHAT DOES A PCS INSTRUMENT CONSIST OF?PinholeDetector(Photomultiplier/AvalanchePhoto Dio

29、de)LaserSample containing particlesComputercontainingcorrelator card (7132)Scattered lightZetasizer HS (High Sensitivity) instruments contain an APD detectorTHE LASER AND THE WAVELENGTHThe laser used in the Zetasizer instruments is a Helium-Neon laser(He-Ne)Its wavelength is 633nm (red light)What do

30、 you mean by wavelength?A laser produces lightof one wavelengthTHE DARK SIDE OF THE MOONREDORANGEYELLOWGREENBLUEINDIGOVIOLETWAVELENGTHEach colour has a different wavelengthRED633nmBLUE488nm633nm488nmTHE INTENSITY OF SCATTERED LIGHTThe intensity of scattered light obtained from a dispersion of partic

31、les is dependent uponLaser wavelength Particle size SCATTERED LIGHT ANDLASER WAVELENGTHGreen light will give approximately 2 times the intensity of scattered light compared to red lightThis is the reason why some people buy a different laser to use with a ZetasizerIf you are trying to measure very s

32、mall particles or not many particles, the intensity of scattered light will be very lowSCATTERED LIGHT AND PARTICLE SIZEDispersion of smallparticlesLaserThe intensity of scattered light from small particlesis equal in all directionsSCATTERED LIGHT AND PARTICLE SIZEDispersion of largeparticlesThe int

33、ensity of scattered light from large particlesis not equal in all directionsLaserINTENSITY OF SCATTERED LIGHT VERSUS ANGLE40608010012005101520253035AngleRelative Intensity1000nm800nm600nm400nm200nmMULTI-ANGLE INSTRUMENTSPeople measuring particles of 300nm and smallerwill only require a 90o fixed ang

34、le instrument (Zetasizer 1000/3000)People measuring particles of 300nm and largerwill require a multi-angle instrument (Autosizer 4800)Laser diffraction (Mastersizer)simultaneouslymeasures the intensity of scattered light at various anglesHOW DOES PCS WORK?All small particles in waterwill move rando

35、mlyThis process is called Brownian motionBecause the water molecules surrounding them are constantly hitting themWhy is that?BROWNIAN MOTION OFLARGE PARTICLESHHOHHOHHOHHOHHOHHOHHOHHOHHOLarge Particles - Slow Brownian MotionBROWNIAN MOTION OFSMALL PARTICLESHHOHHOHHOHHOHHOHHOHHOHHOHHOSmall Particles -

36、 Fast Brownian MotionBROWNIAN MOTION AND SCATTERED LIGHTBecause the scattered waves of lightare interfering with one anotherWhy does this happen?The Brownian motion of the particles causes the scattered light tofluctuate in intensityBROWNIAN MOTION AND SCATTERED LIGHTScreenTwo beams interfere andcan

37、cel each other outresulting in a decreased intensity in the scattered lightLet us consider 2 stationary particlesBROWNIAN MOTION AND SCATTERED LIGHTScreenTwo beams interfere andenhance each otherresulting in an increased intensity in the scattered lightBROWNIAN MOTION AND SCATTERED LIGHTMany scatter

38、ed beams interfere with one anotherresulting in a very complex intensity pattern of specklesScreenConsider many particlesHOW DO WE MEASUREHOW QUICKLY THE SCATTERED LIGHT IS CHANGING?We use a device called a correlatorWe were the firstmanufacturers of correlatorsin the world HOW DO WE MEASUREHOW QUIC

39、KLY THE SCATTERED LIGHT IS CHANGING?Today the correlator is a card which fits into a personal computer(7132)THE CORRELATORThe intensity of thescattered light is measuredat different times by the correlatorThe correlator then calculates how quicklythe signal is changing and thisgives us the particle

40、sizeHow does a correlator work?The 7132 correlator can look at the intensity of scattered light every 50 nanosecondsi.e. 20 million times a second!雪崩式光子電子計數(shù)檢測器n固態(tài)二極管檢測器(Solid state diode detectors)n當光子撞擊時，產(chǎn)生了電子空穴對n產(chǎn)生的高壓加速了電子運動n被加速的電子獲的足夠的能量進一步導致電離度的增加，如同雪崩一樣。n最初的光子能雪崩式產(chǎn)生大量的約106 電子這個數(shù)量級遠大于普通的光電備增器( p

41、hotomultiplier detector)n因此有了新一代的雪崩式光子電子計數(shù)器檢測器應用實例: Absorbing systemsz- 平均粒徑平均粒徑 (nm)多分散度多分散度測定時間測定時間分分計數(shù)率計數(shù)率(KCPS)18.418.418.4345.4346.0346.1180.4179.3181.2177.3177.5178.40.2460.2210.2240.1980.2120.212151515222RUN123456檢測器檢測器PMPMPMAPDAPDAPD10mW He-Ne laser 測碳黑樣品測碳黑樣品計數(shù)率越高越好，結果重復性越好計數(shù)率越高越好，結果重復性越好應用

42、實例: 溶液中的蛋白質51050 100500Diameter (nm)102030% in classIntensity Size distributionz- 平均粒徑平均粒徑 (nm)多分散度多分散度RUN123MEAN10.311.411.010.9 0.50.2240.2430.2440.237 0.011 測量時間測量時間 = 15 分分/次次0.5% 牛血清蛋白牛血清蛋白 (BSA)Stern layerZETA POTENTIALWithin the diffuse layer is a notional boundary (the slipping plane) within

43、 which the particle acts as a single entityThe potential at this boundary is theZETA POTENTIALSlipping planeDiffuse layer-1000mVDistance from particle surfaceSurface potentialZeta potentialZETA 電位與散射體系的穩(wěn)定性Negative zeta potentialPositive zeta potential+30mV-30mV0mV穩(wěn)定穩(wěn)定不穩(wěn)定ZETA 電位與 pH 關系2468101-60-40-2

44、00204060等電點等電點Zeta 電位電位 (mV)pH2穩(wěn)定穩(wěn)定不穩(wěn)定HOW DO WE MEASUREZETA POTENTIAL?Zeta potential is measuredby measuring how quicklyparticles move in an applied electrical fieldHow do we do that?MEASURING PARTICLE MOBILITY IN AN ELECTRIC FIELD+-THE CAPILLARY CELL IN A ZETASIZERGlass Capillary CellPositiveElectr

45、odeNegativeElectrodeCROSSING OF TWO LASER BEAMSInterferenceFringes高分辨Zeta電位技術 M3專利 （2000年7月）常規(guī)電泳法得到的常規(guī)電泳法得到的ZETA電位圖電位圖M3技術得到的技術得到的ZETA電位圖電位圖 圖1、四種標準物質混合的Zeta電位圖 圖2、M3專利技術特征 (4種標準品分別為-50mV,-60mV,-84mV,-108mV) Theory of use of the stationary layer methodnElectrophoresisnElectroosmosisnThe stationary l

46、ayer ElectrophoresisnElectrophoresis is the effect where particles with a net charge when placed in an electric field will migrate towards the electrode with opposite charge.nBecause micron size particles have very low inertia, terminal velocity is reached in microseconds. The actual velocity is det

47、ermined by the charge associated with the particle (zeta potential), the viscosity of the medium and the applied field.Cause -Application of an electric fieldEffect -Particle movementstationary - liquid phasemobile - solid phaseElectroosmosisnElectroosmosis is the movement of a liquid containing ion

48、s, next to a charged surface when a field is applied along the surface.nIn a quartz cell the velocity of the electroosmotic flow is the same order of magnitude as the particle mobilities we wish to measure. This flow takes much longer to establish than electrophoresis, in the order of 10s of millise

49、condsCause -Application of an electric fieldEffect -Liquid movementstationary - solid phasemobile - liquid phaseThe stationary layernThere is only one position in a capillary cell where we can measure the true particle mobility.nIn a capillary which is closed at both ends the liquid returns along th

50、e centre of the cell. We measure where the fluid flow along the cell wall cancels out with the return flow in the centre of the cell.StationaryLayerAvoiding electroosmosisnThe best solution would be to avoid electroosmosis altogether. The mobility of the particles at any point in the cell would then

51、 be the true mobilitynUsing a dip cell is one way to remove the effects of electroosmosis, but there are a lot of disadvantages to this techniquenAnother approach is to neutralise the charge on the cell walls with a coating, but this always wears off and is application specificnA recently described

52、alternative is to reverse the applied field rapidly enough that electroosmosis is insignificant (FFR), this gives an accurate mean, but is low resolutionReversing the applied fieldnAll systems that measure mobilities using LDV (laser Doppler velocimetry) reverse the applied field periodically.nThis

53、is to reduce the polarisation of the electrodes that is inevitable in a conductive solution. This is usually set to about 1 second to allow stabilisation of the fluid flow.Electroosmosis in a slowly reversing fieldStationaryPlaneFFR (Fast field reversal)nIf the field is reversed much more rapidly, i

54、t is possible to show that the particles reach terminal velocity, while the fluid flow due to electroosmosis is insignificant.nThe mean zeta potential calculated by this technique is therefore very robust as the measurement position in the cell is not critical.nHowever, as the velocity of the partic

55、les is sampled for such a short period of time, information about the distribution is degraded. This is what is addressed by the M3 techniqueElectroosmotic flow in a fast reversing fieldStationaryPlaneWhat is M3?nA new method of making zeta potential measurements that uses the best features of both

56、stationary layer and FFR techniquesnNo cell alignmentANDnImproved resolutionThis method requires:nA new cell typenNew software (version 1.51)The best of both worldsnM3 uses measurements of both slow field reversal and fast field reversal, hence the name Mixed Mode Measurement.nIn addition to the zer

57、o field measurement, which gives a better measurement of the actual distribution width, two measurements are done for each zeta potential determination.1. A fast field reversal measurement provides the accuracy and stability of the result2. Information from the slow field reversal improves the resol

58、ution.nBecause we now use the fast field reversal to calculate the mean, we can extract more resolution from the slow field reversal mode, without affecting the accuracy or repeatability of the mean.The best of both worldsnAn M3 measurement consists of:nAn FFR measurement at 1000Hz at the cell centr

59、e. This gives an accurate determination of the mean.nA zero field measurement is performed to measure the effect of Brownian motion broadeningnA slow field reversal measurement at the cell centre. This gives better resolution, however the mobility values will be shifted by the effect of electroosmos

60、is.nThe means calculated from the FFR and slow field measurements are subtracted to give the electroosmotic flow. nThis value is used to normalise the slow field reversal distributionnThe value for electroosmosis is used to calculate the zeta potential of the cell wallZero field correctionnThis meas