Recent Developments on Resolution and Applicability of Capillary Hydrodynamic Fractionation (CHDF)

毛細(xì)管流體分離技術(shù)(CHDF)分辨率和應(yīng)用的新的發(fā)展

J. Gabriel DosRamos,

Matec Applied Sciences, 56 Hudson St., Northborough, MA 01532 USA

Abstract：

摘要：

Capillary Hydrodynamic Fractionation (CHDF) is a high-resolution particle size distribution (PSD) analysis technique. CHDF is used to measure the PSD of colloids in the particle size range of 5 nm to 3 microns.

CHDF fractionation occurs as an eluant or carrier fluid carries the particles downstream in a capillary tube. Large particles exit the fractionation capillary ahead of smaller particles. Particle fractionation occurs because of the combination of the eluant parabolic velocity profile (laminar flow), size exclusion of the particles at the capillary wall, and colloidal forces.

The aim of this study was to expand CHDF’s applicability to a broader class of colloidal systems. This can widen CHDF’s usefulness as a particle sizing technique.

毛細(xì)管流體分離（CHDF）技術(shù)是一種高分辨的粒度分布（PSD）檢測(cè)技術(shù)。毛細(xì)管流體分離技術(shù)（CHDF）用于測(cè)量粒徑在5nm-3μm 范圍內(nèi)膠體的粒度分布（PSD）。

毛細(xì)管流體分離(CHDF)技術(shù)是以洗脫液或載體流體在毛細(xì)管中攜帶顆粒順流而下的形式發(fā)生的。大顆粒先于小顆粒退出分離毛細(xì)管。顆粒分離是由于洗脫物拋物線速度剖面(層流)、在毛細(xì)管內(nèi)顆粒的尺寸排斥和膠體力的共同作用而發(fā)生的。

本研究的目的是將毛細(xì)管流體分離(CHDF)應(yīng)用于更廣泛的膠體系統(tǒng)。這可以增加毛細(xì)管流體分離(CHDF)技術(shù)在粒度分析方面的應(yīng)用。

Introduction：

介紹：

Particle sizing techniques can be grouped into High-Resolution (Fractionation) and Ensemble techniques (1). High-Resolution (HR) techniques are characterized by the fact that particles are fractionated according to size and/or mass during particle size analysis. Ensemble techniques perform measurements on all particles simultaneously without physical separation. HR particle size analyzers include Capillary Hydrodynamic Fractionation (CHDF), Field-Flow Fractionation, Single-Particle Counting, and Disc Centrifugation. Ensemble techniques include Laser Diffraction, Photon-Correlation Spectroscopy (PCS), acoustic-attenuation spectroscopy, and Turbidimetry. Electron Microscopy is in a class by itself as it offers high resolution but particles are not fractionated during analysis.

顆粒測(cè)量技術(shù)可分為高分辨(分離)技術(shù)和Ensemble粒度分析技術(shù)《1》。高分辨率技術(shù)的特點(diǎn)是因?yàn)樵陬w粒測(cè)量分析的過(guò)程中，粒子可以根據(jù)大小或者質(zhì)量的不同而進(jìn)行分離。Ensemble粒度分析技術(shù)在沒(méi)有物理分離的情況下對(duì)所有粒子同時(shí)進(jìn)行測(cè)量。高分辨的粒度分析技術(shù)包括毛細(xì)管流體分離(CHDF)、場(chǎng)流分離、單顆粒計(jì)數(shù)和圓盤離心組成。Ensemble粒度分析技術(shù)包括激光衍射、數(shù)字相關(guān)技術(shù)(PCS)、聲衰減光譜和濁度測(cè)定方法等。電鏡也屬于高分辨粒徑測(cè)量的技術(shù)，但是其并不能在分析的過(guò)程中將顆粒進(jìn)行分離。

補(bǔ)充說(shuō)明（內(nèi)容來(lái)自網(wǎng)絡(luò)）：

1. 場(chǎng)流分離（Field flow fractionation—FFF）為適用于大分子、膠體和微粒的分離技術(shù)，使欲分離成分之流液流經(jīng)上下平板構(gòu)成扁平帶狀通道，并將一場(chǎng)垂直施加于通道。場(chǎng)將導(dǎo)致不同成分處在距下壁不同的位置上，移動(dòng)速度因而不同，以達(dá)到分離的目的。 場(chǎng)流分離，可將“流”通過(guò)不對(duì)稱場(chǎng)如電場(chǎng)，重力場(chǎng)，熱場(chǎng)或半透膜。

該技術(shù)基本原理是大分子流過(guò)扁平通道，同時(shí)受到水平（channel flow）和垂直方向（cross flow）的流場(chǎng)作用；尺寸相對(duì)小的分子，受垂直方向的作用力較小，而向扁平通道中心平移擴(kuò)散；而尺寸相對(duì)較大的分子，受垂直方向的作用力較大而更靠近聚集壁（accumulated wall）。從而在垂直方向形成尺寸（size）梯度。而流體在扁平通道內(nèi)，越靠近中心，流速越快，而越靠近邊緣，流速越均勻和越緩慢。因此，尺寸相對(duì)較小的組分先被后端檢測(cè)器檢測(cè)到；而較大尺寸的組分隨后被檢測(cè)。

2. Disc Centrifugation圓盤離心沉降法的原理是重力或者離心力使得懸浮在樣品轉(zhuǎn)盤腔內(nèi)的顆?？梢援a(chǎn)生沉降或離心運(yùn)動(dòng)。大顆粒運(yùn)動(dòng)較快，小顆粒運(yùn)動(dòng)較慢，隨著時(shí)間的增加，大小顆粒自然分級(jí)并依次通過(guò)靠近轉(zhuǎn)盤腔底內(nèi)部的檢測(cè)器，因而具有高的分辯率。 

HR techniques offer a strong advantage in that they produce true particle size distribution (PSD) data. HR-based devices can in principle detect the presence of multiple particle size populations without making significant assumptions. On the other hand, HR devices tend to be more complicated to operate than ensemble instruments. Ensemble instruments produce mainly mean particle size and standard deviation data. Any mean particle size value can be produced by an infinite number of PSD curves. This ill-conditioned problem, along with the fact that calculated PSD’s vary significantly with minor noise in the raw data, force most ensemble devices to assume a priori the shape of the PSD (2). Despite these issues, ensemble devices are much more widely used than HR instruments. The two main reasons seem to be the following. Ensemble instruments are easier to use, and are more widely applicable to different types of dispersion/colloidal samples.

這種高分辨率的技術(shù)在真實(shí)的粒度分布（PSD）表征方面有非常明顯的優(yōu)勢(shì)。一方面，基于這種高分辨率的技術(shù)可以用來(lái)分析多組分的復(fù)雜粒度體系，并不需要作出任何假設(shè)。但另一方面，這種高分辨率的技術(shù)設(shè)備運(yùn)行往往相對(duì)統(tǒng)Ensemble粒度分析操作更復(fù)雜。Ensemble粒度分析技術(shù)可以提供平均粒徑和標(biāo)準(zhǔn)偏差。任何平均粒徑值都可以由無(wú)限條PSD曲線生成。這個(gè)原理的缺陷問(wèn)題，會(huì)使得在只有少量噪聲的情況下原始數(shù)據(jù)中計(jì)算出的PSD值變化很大，這迫使大多數(shù)Ensemble粒度分析設(shè)備需要預(yù)先假定PSD的形狀《2》。盡管存在這些問(wèn)題，Ensemble粒度分析設(shè)備比這種高分辨的技術(shù)應(yīng)用往往更廣泛。主要是有兩個(gè)主要原因：Ensemble粒度分析設(shè)備更易于使用，更廣泛地適用于不同類型的分散/膠體樣品。

Figure 1- Particle size-based fractionation in CHDF.

圖1. CHDF的顆粒分離示意圖

Figure 1 describes the particle size-based fractionation process in CHDF. Larger particles exit the fractionation open capillary ahead of smaller ones (3). A UV detector is typically used as a particle-concentration detector. Such particle fractionation occurs because of a particle-size exclusion effect, plus colloidal forces affecting the particle motion. The latter consist mainly of particle/capillary electric double layer repulsion, and a lift force exerted by the moving fluid on the particles (4).

圖1描述了毛細(xì)管流體分離(CHDF)技術(shù)中不同顆粒大小的分離過(guò)程的原理示意圖。較大的顆粒比較小的顆粒先離開(kāi)分離的毛細(xì)管《3》。一個(gè)紫外線探測(cè)器被用來(lái)檢測(cè)粒子濃度。毛細(xì)管流體分離(CHDF)實(shí)現(xiàn)的粒子分離是由于粒子大小的排斥效應(yīng)，加上影響粒子運(yùn)動(dòng)的膠體力。后者主要由顆粒電荷/毛細(xì)管電荷雙電層斥力和運(yùn)動(dòng)的流體對(duì)微粒施加的升力組成《4》。

Figure 2. Two different samples analyzed by CHDF. Both have the same Volume-average (mean) particle size of 226 nm even though the PSD’s are different.

圖2-兩個(gè)不同的樣品的CHDF測(cè)試數(shù)據(jù).

兩個(gè)樣品相同的體積平均粒徑但是PSD是不一樣的。

Figure 2 shows CHDF2000 PSD data from two different polystyrene samples with the same volume-average mean particle size value of 226 nm even though their PSD’s are noticeably different. This data exemplifies the risks of relying exclusively on mean particle size data. These samples will behave differently despite their identical mean particle size.

圖2顯示了兩種不同的聚苯乙烯樣品的CHDF2000 PSD測(cè)試數(shù)據(jù)，即使他們具有相同的體積平均粒徑值226 nm，但是它們的PSD值有明顯的不同。這些數(shù)據(jù)說(shuō)明了*依賴平均粒徑數(shù)據(jù)的風(fēng)險(xiǎn)。盡管這些樣品的平均粒徑相同，但它們的PSD分布卻不同。

It is in principle possible for a sample with a 226 nm mean particle size not to contain any 226 nm particles. This constitutes another disadvantage of relying on mean particle size data alone.

對(duì)于平均粒徑為226 nm的樣品，實(shí)際上卻可以并不包含任何226 nm的顆粒。這構(gòu)成了僅依賴平均粒徑數(shù)據(jù)的另一個(gè)缺點(diǎn)。

This paper describes efforts to expand the applicability of CHDF to different types of dispersed systems, including expanding its particle size analysis range. Also, a process on-line CHDF setup with automated sample dilution is presented.

本文描述了毛細(xì)管流體分餾（CHDF）技術(shù)在不同類型的分散系統(tǒng)中的適用性，包括擴(kuò)大其粒度分析范圍。同時(shí)，提出了一種自動(dòng)稀釋樣品的毛細(xì)管流體分離(CHDF)在線檢測(cè)方法。

Experimental：

實(shí)驗(yàn)部分：

CHDF measurements were performed using a commercial CHDF2000 high resolution particle size analyzer from Mass Applied Sciences, Northborough, MA (5). Various colloidal samples were used. Polystyrene samples were obtained from Duke Scientific (Indianapolis, IN), and Seradyn (Indianapolis,
IN).

高分辨率的毛細(xì)管流體分離(CHDF)粒度測(cè)量技術(shù)，是由位于美國(guó)-馬薩諸塞州Mass Applied Science（MAS）公司研發(fā)和生產(chǎn)的《5》。并測(cè)試了不同的膠體樣品。聚苯乙烯粒子樣品來(lái)自于Duke和Seradyn (Indianapolis, IN)。

Nanoparticle Size Analysis：

納米顆粒大小分析：

Small particles, especially under 50 nm, are becoming more widely manufactured and employed in various intermediate and final colloidal products. Accurate particle size analysis of these small particles is essential. Small particles offer a large total surface area. Secondary smaller particle size populations can be unexpectedly present in any dispersion. Such smaller particles can sharply influence the performance of any dispersion. Additionally, a small number of larger particles can posse difficulties, e.g., larger particles in inkjet printing inks can plug ink conduits in today’s inkjet printers.

小顆粒，特別是50nm以下的小顆粒，正在越來(lái)越廣泛地被制造和應(yīng)用于各種膠體的中間和終產(chǎn)品中。準(zhǔn)確分析這些小顆粒的粒徑是至關(guān)重要的。小顆粒提供了很大的總表面積。在任何分散體中都可能出現(xiàn)次級(jí)較小粒徑的粒子群。如此小的粒子可以極大地影響任何分散體系的性能。此外，少數(shù)較大的顆粒會(huì)造成困難，例如，在噴墨打印機(jī)中較大的顆粒會(huì)堵塞墨道。

Particle sizing of nanoparticles is difficult for most particle sizing techniques. Because of refractive index issues, as well as the fact that larger particles mask smaller particles, ensemble-type measurements such as Laser Diffraction and Photon Correlation Spectroscopy (PCS) have difficulty analyzing such nanoparticles. High-resolution devices such as disc centrifuges are also limited due to the lack of tendency of nanoparticles to sediment, even under strong centrifugal fields.

納米粒子的粒徑測(cè)定是目前大多數(shù)粒徑測(cè)定技術(shù)的難點(diǎn)。由于折射率問(wèn)題，以及大顆粒掩蓋小顆粒的事實(shí)，像激光衍射和光子相關(guān)光譜(PCS)等Ensemble粒度分析技術(shù)很難分析這樣的納米顆粒。像圓盤離心機(jī)這樣的高分辨率設(shè)備也會(huì)受到此限制，因?yàn)榧词乖趶?qiáng)離心場(chǎng)下，納米粒子也不易沉積。

Figure 3. Effects of capillary inner diameter and eluant ionic strength and average velocity on CHDF resolution and particle size fractionation range.

圖三-毛細(xì)管內(nèi)徑、淋洗液離子強(qiáng)度和平均流速對(duì)

毛細(xì)管流體分離(CHDF)分辨率和粒度分離范圍的影響。

Fig. 3 illustrates the effects of capillary ID, eluant average velocity, and eluant ionic strength on the resolution and particle-size fractionation range. As the capillary ID increases, so does the sample volume in the capillary. This increase in sample volume is due to the fact that the waste/fractionation split ratio changes (6), i.e. more sample flows into the fractionation capillary relative to the “waste” stream. Such increase in fractionated-sample volume results in stronger particle detection in the CHDF particle-concentration detector, usually a UV detector.

圖3描述了毛細(xì)管內(nèi)徑、洗脫液平均流速、洗脫液離子強(qiáng)度對(duì)顆粒分離范圍和分辨率的影響。隨著毛細(xì)管內(nèi)徑的增加，毛細(xì)管中的樣品體積也隨之增加。樣品體積的增加是由于廢廢液/分離樣品分流比的變化《6》，相對(duì)于廢液流，更多的樣品流入分餾毛細(xì)管。分餾樣品體積的增加使得毛細(xì)管流體分離(CHDF)顆粒濃度檢測(cè)器（通常是UV檢測(cè)器）的顆粒檢測(cè)能力增強(qiáng)。

Conversely, fractionation resolution increases as the capillary ID is reduced (7). This is due to several compounding factors as follows: (i) the particle exclusion layer is larger relative to the capillary ID, (ii) the lift force is stronger, and (iii) the particle fractograms are narrower due to lower axial dispersion.

相反，隨著毛細(xì)管內(nèi)徑的減少，分離的分辨率增加《7》。這主要是由以下幾個(gè)復(fù)合因素造成的:（i）顆粒排斥層相對(duì)于毛細(xì)管內(nèi)徑較大；（ii）升力較強(qiáng)；(iii)由于軸向彌散較低，顆粒斷口較窄。

The upper particle size limit decreases with decreasing capillary ID. Physically, larger particles can flow in a larger-ID fractionation capillary; also, the lift force is lower for larger-ID capillaries; this allows fractionation among larger particles.

粒徑上限隨毛細(xì)管內(nèi)徑的減小而減小。物理上，較大的顆?？梢栽谳^大的內(nèi)徑分餾毛細(xì)管中流動(dòng)；同樣，對(duì)于較大的內(nèi)徑毛細(xì)管，提升力較低，可以用來(lái)進(jìn)行較大的顆粒的分離。

The eluant average velocity also plays a role on the resolution and particle size range. As the eluant average velocity in increased, large-particle size fractograms become narrower. This Fractogram narrowing is due to the increase in lift force strength which forces larger particles to travel closer together. As the lift force increases, the upper particle size fractionation limit decreases similarly to reducing the capillary ID (8).

淋洗液平均流速也對(duì)其分辨率和粒徑檢測(cè)范圍也有影響。隨著洗脫液平均流速的增加，大顆粒尺寸的斷口變得越來(lái)越窄。這種斷口變窄是由于提升力強(qiáng)度的增加，從而迫使較大的顆粒更接近地一起移動(dòng)。隨著升力的增大，顆粒粒度的分離上限減小，與減小毛細(xì)管內(nèi)徑值結(jié)果相似《8》。

Suitable capillary ID and length, plus the eluant ionic strength and mean velocity can be combined to produce high resolution PSD data as shown in figures 4 and 5. Data is shown for the fractionation of eight particle size populations in less than 10 minutes.

合適的毛細(xì)管內(nèi)徑和長(zhǎng)度，加上合適的洗脫液離子強(qiáng)度和平均速度，可以組合起來(lái)得到高分辨率的PSD數(shù)據(jù)，如圖4和5所示。數(shù)據(jù)顯示了在不到10分鐘內(nèi)對(duì)8個(gè)粒徑粒子的分離。

Figure 4. CHDF fractionation UV-detector raw data for a blend of 8 polystyrene calibration standards.

圖4-CHDF-UV檢測(cè)器對(duì)8種混合聚苯乙烯標(biāo)準(zhǔn)粒子的原始測(cè)試數(shù)據(jù)

Figure 5. CHDF PSD data for an 8-mode polystyrene blend.

圖5-8種聚苯乙烯共混物的CHDF PSD數(shù)據(jù)。

This blend is composed of (from left to right on the raw-data graph) 800, 605, 420, 310, 240, 150, 60, and 20 nm. The peak separation on the raw data graph can be enhanced further by simply lengthening the fractionation time. The raw data peaks appear more overlapped than on the PSD. The reason is that a deconvolution procedure has been applied in the PSD computations (9). The deconvolution computations are similar to those used in Gel Permeation Chromatography for incorporating into the PSD computations axial dispersion of particles during capillary flow. Axial dispersion broadens the Fractogram width.

這種混合物由800、605、420、310、240、150、60和20nm組成（從原始數(shù)據(jù)圖的左到右）。通過(guò)簡(jiǎn)單地延長(zhǎng)分離時(shí)間，可以進(jìn)一步增強(qiáng)原始數(shù)據(jù)圖上的峰分離。原始數(shù)據(jù)峰值看起來(lái)比PSD上的重疊更多。其原因是在PSD計(jì)算中應(yīng)用了反卷積方法《9》。反卷積計(jì)算類似于凝膠滲透色譜法，用于將毛細(xì)管流動(dòng)過(guò)程中顆粒的軸向彌散納入PSD計(jì)算。軸向彌散使裂縫寬度變寬。

補(bǔ)充說(shuō)明（內(nèi)容來(lái)自網(wǎng)絡(luò)）：

1. Deconvolution反卷積算法：

在數(shù)學(xué)中，反卷積是一種基于算法的過(guò)程，用于反轉(zhuǎn)卷積對(duì)記錄數(shù)據(jù)的影響。 反卷積的概念廣泛用于信號(hào)處理和圖像處理技術(shù)。 由于這些技術(shù)反過(guò)來(lái)在許多科學(xué)和工程學(xué)科中廣泛使用，因此反卷積可以應(yīng)用到許多領(lǐng)域。反卷積是信號(hào)處理中一類基本問(wèn)題,廣泛應(yīng)用于信道均衡、圖像恢復(fù)、語(yǔ)音識(shí)別、地震學(xué)、無(wú)損探傷等領(lǐng)域,也可應(yīng)用于未知輸入估計(jì)和故障辨識(shí)問(wèn)題。

褶積(又名卷積)和反褶積(又名去卷積)是一種積分變換的數(shù)學(xué)方法,在許多方面得到了廣泛應(yīng)用。在泛函分析中，卷積、旋積或摺積(英語(yǔ)：Convolution)是通過(guò)兩個(gè)函數(shù)f 和g 生成第三個(gè)函數(shù)的一種數(shù)學(xué)算子，表征函數(shù)f 與g經(jīng)過(guò)翻轉(zhuǎn)和平移的重疊部分函數(shù)值乘積對(duì)重疊長(zhǎng)度的積分。

2. Gel Permeation Chromatography凝膠滲透色譜法：

凝膠滲透色譜(Gel Permeation Chromatography、GPC)是1964年，由J.C.Moore首先研究成功。不僅可用于小分子物質(zhì)的分離和鑒定，而且可以用來(lái)分析化學(xué)性質(zhì)相同分子體積不同的高分子同系物。(聚合物在分離柱上按分子流體力學(xué)體積大小被分離開(kāi)）。

CHDF offers a useful alternative for nanoparticle analysis due to the fact that larger particles do not mask the presence of small particles, as well as, nanoparticle analysis is as easy and accurate as for larger particles. However, CHDF also faces difficulties in analyzing particles smaller than 20 nm. These particles are difficult to quantify in the presence of larger particles due to large differences in UV-light extinction cross section (10). These difficulties are shown in the well-known Beer-Lambert’s law equation as follows:

D.O. = N Rext χ           [1]

Where D.O. is the UV-detector output, N is the number of particles per unit volume, Rext is the particle extinction cross section, and χ is the UV-detector flow-cell path length. Equation [1] allows the calculation of N for each individual slice of particles exiting the CHDF fractionation capillary. N computations are susceptible to minor noise in D.O. when a sample contains particles under 20 nm along with larger particles, e.g. particles over 500 nm.

由于大顆粒不會(huì)掩蓋小顆粒的存在，毛細(xì)管流體分離(CHDF)為納米顆粒分析提供了一種有用的替代方法，讓納米顆粒分析與大顆粒分析一樣簡(jiǎn)單和準(zhǔn)確。然而，CHDF在分析小于20nm的顆粒時(shí)也會(huì)面困難。由于紫外消光截面的巨大差異，這些粒子在較大粒子存在時(shí)很難量化《10》。這些困難顯示在著名的比爾-朗伯定律方程如下：

D.O. = N Rext χ           [1]

這里D.O.是紫外線探測(cè)器輸出，N是單位體積的粒子數(shù)，Rext是粒子消光界面，χ是紫外檢測(cè)器流動(dòng)池路徑長(zhǎng)度。方程允許計(jì)算出毛細(xì)管流體分離(CHDF)細(xì)管中每一片顆粒的N。當(dāng)樣品含有小于20nm的粒子和較大的粒子（例如大于500nm的粒子）時(shí)， N的計(jì)算容易D.O.中微小噪聲的影響。

Figure 6. Extinction cross section for polystyrene particles in water. Curve generated from Mie theory computations.

圖6-由Mie理論計(jì)算得到的聚苯乙烯顆粒在水中的消光截面。

Figure 6 shows an extinction cross section curve for polystyrene particles in water. This curve was generated from Mie-theory computations built into the operating software on the commercial CHDF2000 device.

圖6顯示了聚苯乙烯顆粒在水中的消光截面曲線。此曲線是CHDF2000設(shè)備上的操作軟件中，內(nèi)置的Mie理論計(jì)算生成的。

Figure 6 shows that there are several orders of magnitude between the Rext of particles smaller than 20 nm and those larger than 500 nm. Consequently, small D.O. errors become largely amplified in the computation of N.

從圖6可以看出，小于20nm和大于500nm的顆粒之間存在幾個(gè)數(shù)量級(jí)的Rext。因此，微小的D.O.誤差在N的計(jì)算中被極大地放大。

Figure 7. CHDF UV-detector raw data output for a 5-nm nominal particle size silica.

圖7- CHDF紫外檢測(cè)器得到的5nm二氧化硅粒子的原始輸出數(shù)據(jù)。

Figure 8. CHDF PSD for a 5-nm nominal particle size silica sample.

圖8- CHDF得到的5nm二氧化硅粒子的粒度分布圖。

Despite the challenges described above, the CHDF2000 device was able to accurately perform particle sizing measurements of silica particles under 20 nm as shown in Figures 7 and 8.

盡管存在上述挑戰(zhàn)，美國(guó)MAS的CHDF2000設(shè)備仍能夠準(zhǔn)確地對(duì)20nm以下的二氧化硅顆粒進(jìn)行準(zhǔn)確的粒度分析，如圖7和8所示。

The accurate measurement of these small particles was achieved by maximizing resolution and particle-detection sensitivity. This required optimizing the combination of suitable capillary diameter and length, and eluant ionic strength and average velocity.

美國(guó)MASS生產(chǎn)研發(fā)CHDF系列設(shè)備通過(guò)優(yōu)化合適的毛細(xì)管直徑和長(zhǎng)度、洗脫液離子強(qiáng)度和平均流速的組合，讓設(shè)備的分辨率和粒子檢測(cè)靈敏度達(dá)到很大化，實(shí)現(xiàn)了對(duì)這些小粒子的精確測(cè)量。

The CHDF raw data in figure 7 shows two main peaks located at 8.5 and 8.7 minutes. The peak at 8.7 minutes is believed to originate from UV-absorbing molecules in the sample such as surfactants, electrolytes, and acid or base molecules (11). These molecules exit the capillary last because their particle size is smaller than that of the silica particles. The molecular peak does not appear in the PSD graph of figure 8 because its particle size is below the low computational limit of 1 nm.

從圖7的原始數(shù)據(jù)可以看出，在8.5和8.7分鐘出有兩個(gè)主要的峰。8.7分鐘時(shí)的峰值被認(rèn)為是來(lái)自樣品中的紫外線吸收分子，如表面活性劑、電解質(zhì)、酸或堿分子《11》。這些分子后離開(kāi)毛細(xì)管是因?yàn)樗鼈兊牧叫∮诙趸桀w粒。分子峰不出現(xiàn)在圖8的PSD圖中，因?yàn)槠淞降陀?nm的計(jì)算下限。

Figure 8 presents the PSD for this silica sample. A lognormal PSD shape is obtained ranging from 1 nm to 30 nm. The mode is located at 4 nm.

圖8顯示了這個(gè)二氧化硅樣品的PSD分布。得到了1～30nm的對(duì)數(shù)正態(tài)PSD形狀。PSD的峰值位于4nm處。

In order to achieve the maximum resolution required for these small particles (7) a low ionic strength (0.1 mM) carrier fluid was used in conjunction with a 5-micron ID fused silica capillary.

為了獲得檢測(cè)這些小顆粒所需的大分辨率《7》，低離子強(qiáng)度(0.1 mM)載體流體與5μm管徑熔融石英毛細(xì)管一起使用。

CHDF Particle Size Analysis of Micron-Sized Particles：

CHDF技術(shù)分析微米級(jí)顆粒：

CHDF has been commonly used for analysis of particles below 1 micron in size. As mentioned above, larger particles are typically subject to a “Lift Force” in the fractionation capillary. The lift force pushes larger particles toward the center of the capillary. The Lift force is proportional to the ratio of particle to capillary radii, and to the eluant average velocity. Thus, lowering the eluant average velocity along with using larger-ID fractionation capillaries reduce the lift force and extend the CHDF particle size upper limit.

毛細(xì)管流體分離(CHDF)通常用于分析1μm以下的顆粒。如前所述，較大的顆粒在分離毛細(xì)管中通常受到升力的作用。升力將較大的顆粒推向毛細(xì)管的中心。升力與顆粒毛細(xì)管半徑之比及洗脫液平均速度成正比。因此，降低洗脫液平均流速，同時(shí)使用大粒徑分離毛細(xì)管，可以降低升力，提高CHDF粒徑檢測(cè)上限。

Figure 9. CHDF UV-detector raw data output for a blend of 5μm, 1μm, and 0.1μm polystyrene latex standards. Sodium benzoate “marker” is injected about 1 minute after the blend.

圖9- 5,1, 0.1μm三種混合體系的CHDF UV檢測(cè)器原始數(shù)據(jù)圖。

苯甲酸鈉“標(biāo)記物”在混合后約1分鐘注射。

Fig. 9 shows CHDF UV-detector vs. time fractionation data for a blend of 5, 1, and 0.1-micron polystyrene standards. The marker is injected about one minute after the blend. This data shows that CHDF fractionation is indeed able to fractionate particles larger than one micron. However, it is desirable to increase the fractionation resolution further in order to enhance particle size analysis capability for these larger particles. Further work is in progress.

圖9顯示了5μm、1μm和0.1μm聚苯乙烯標(biāo)準(zhǔn)混合物的CHDF UV檢測(cè)器輸出數(shù)據(jù)與時(shí)間關(guān)系的原始數(shù)據(jù)。苯甲酸鈉“標(biāo)記物”大約在混合后一分鐘注射。這些數(shù)據(jù)表明，毛細(xì)管流體分離(CHDF)技術(shù)確實(shí)能夠分餾大于1μm的顆粒。然而，為了提高這些較大顆粒的粒度分析能力，我們希望進(jìn)一步提高分餾分辨率。進(jìn)一步的工作正在進(jìn)行中。

On-Line Development

在線擴(kuò)展

Today, there is a lack of (process) in-line, at-line, or on-line particle size analyzers suitable for analysis of liquid dispersions. Process particle sizers can become a vital component of slurry / dispersion / latex / emulsion production. Such analyzers can provide labor savings, as well as ensure product quality. Process particle sizers must be highly accurate, reproducible, precise, and reliable (12).

目前，還缺乏適合分析液體分散的在位，近線或在線的粒度分析儀。工藝檢測(cè)的粒度儀可以成為泥漿/分散液/乳膠/乳液生產(chǎn)的重要組成部分。這樣的粒度分析儀可以節(jié)省勞動(dòng)力，同時(shí)保證產(chǎn)品質(zhì)量。在線工藝粒度儀必須高度精確、可重復(fù)、精確和可靠《12》。

補(bǔ)充說(shuō)明（內(nèi)容來(lái)自網(wǎng)絡(luò)）：

1. in-line/at-line/on-line的區(qū)別：

in line 可對(duì)應(yīng)為在線，樣品在生產(chǎn)線上，檢測(cè)裝置也在生產(chǎn)線上，樣品檢測(cè)不影響工藝流；on line可對(duì)應(yīng)為隨線，檢測(cè)裝置在生產(chǎn)線上，樣品從生產(chǎn)線的工藝流中轉(zhuǎn)到檢測(cè)裝置中完成檢驗(yàn)；at line可對(duì)應(yīng)近線，首先樣品肯定是離線的，從生產(chǎn)線取出，在靠近生產(chǎn)線的地方檢測(cè)。

2014年2月份歐盟出的工藝指南中對(duì)這三個(gè)詞的定義如下：

At line: Measurement where the sample is removed, isolated from, and analyzed in close proximity to the process stream. At line 樣品從工藝流中移除、隔開(kāi)，并且在靠近工藝流的地方分析的檢測(cè)。

On line: Measurement where the sample is diverted from the manufacturing process and not returned to the process stream. On line 檢測(cè)樣品從生產(chǎn)工藝中轉(zhuǎn)移出來(lái)并不返回工藝流中。

In line: Measurement where the sample is analyzed within the process stream and not removed from it. In line 樣品在工藝流中進(jìn)行檢測(cè)并不從中移除。

Figure 10. On-line CHDF setup equipped with sample auto-dilution.

圖10。CHDF配備樣品自動(dòng)稀釋的在線設(shè)置。

Fig. 10 shows a schematic diagram of an on-line CHDF device. The CHDF2000 unit used here is identical to the off-line device available commercially (Matec Applied Sciences, Northborough, MA). With the off-line device, samples are injected into the fractionation capillary using either an on-board manual HPLC type injection valve or an HPLC auto-sampler. In the on-line setup, the sample flows directly from the process into an automated injection valve. The automated injection valve is actuated by the CHDF2000 on-line software in order to make sample injections every 5-10 minutes.

圖10為在線CHDF裝置的原理圖。這里使用的組件單元與美國(guó)MAS市售的脫機(jī)設(shè)備CHDF2000*相同(Mass Applied Sciences, 馬薩諸塞州, MA)。通過(guò)脫機(jī)裝置，樣品可通過(guò)車載手動(dòng)高效液相色譜注射閥或高效液相色譜自動(dòng)進(jìn)樣器注入分餾毛細(xì)管。在在線設(shè)置中，樣品直接從產(chǎn)線流向一個(gè)自動(dòng)注入閥。自動(dòng)進(jìn)樣閥由CHDF2000在線軟件驅(qū)動(dòng)，每5-10分鐘進(jìn)樣一次。

This particular arrangement has been used with a batch-polymerization reactor. This on-line device can also be used with continuous or semi-continuous reactors, as well as steady-state slurry streams.

這種特殊的排列方式已用于分批聚合反應(yīng)器。該在線裝置也可用于連續(xù)或半連續(xù)反應(yīng)器，以及穩(wěn)態(tài)泥漿流的反應(yīng)監(jiān)測(cè)。

The percent solids level of a batch polymerization reactor starts at zero and increases with time (13). The on-line CHDF setup must be able to handle this constant increase (CHDF analysis is typically performed in the weight-percent solids range of 0.1 to 5%). The analysis process is as follows:

間歇式聚合反應(yīng)器的固體含量從零開(kāi)始隨時(shí)間逐漸增加《13》。在線CHDF軟件設(shè)置必須能夠處理這種恒定的增加(CHDF分析通常在重量-固體百分比0.1到5%的范圍內(nèi)執(zhí)行)。分析過(guò)程如下：

A “drip” line connected to the reactor system takes a steady stream of sample through the remotely-actuated (HPLC) injection valve. The sample is diluted as needed at point D. The injection valve automatically takes samples from the drip line and performs sample injections into the CHDF fractionation capillary every few minutes. CHDF eluant continuously flows through the injection valve in order to carry the samples into the fractionation capillary. The dilution valve sets the diluent vent (Y)/dilution (D) split ratio.

連接到反應(yīng)器系統(tǒng)的“滴水”管線通過(guò)遠(yuǎn)程驅(qū)動(dòng)（HPLC）注射閥獲取穩(wěn)定的樣品流。樣品按需要在D點(diǎn)稀釋。注入閥自動(dòng)從滴管中抽取樣品，每隔幾分鐘將樣品注入CHDF分離毛細(xì)管。CHDF洗脫液通過(guò)注入閥連續(xù)流動(dòng)，將樣品帶入分離毛細(xì)管。稀釋閥設(shè)置稀釋液排出（Y）/ 稀釋液（D）分流比。

In order to eliminate the need for a diluent pump, the effluent (E) from the CHDF is used as diluent. E is split at the dilution valve into a vented (Y), and a diluent (DFR) portion.

為了消除稀釋泵的需要，CHDF的流出物（E）被用作稀釋劑。E在稀釋閥處分成一個(gè)排出(Y)和一個(gè)稀釋劑(DFR)部分。

Valves T1 and T2 allow the use of an HPLC auto-sampler for calibration standard analysis. The operator can thus perform periodic performance tests of the on-line CHDF setup.

閥門T1和T2允許使用高效液相色譜自動(dòng)采樣器進(jìn)行校準(zhǔn)標(biāo)準(zhǔn)分析。因此，操作員可以對(duì)聯(lián)機(jī)CHDF設(shè)置執(zhí)行定期性能測(cè)試。

The CHDF software calculates the area under each Fractogram. The dilution level is calculated by comparing the current Fractogram area to a pre-established suitable area value as follows:

DFR = C*PA/FA        [2]

CHDF軟件計(jì)算每個(gè)分形圖下的面積。稀釋水平的計(jì)算方法是將當(dāng)前的分形圖面積與預(yù)先設(shè)定的適當(dāng)面積值進(jìn)行比較，如下所示：

DFR = C*PA/FA        [2]

Where DFR is the diluent flow rate, C is a constant, PA is the pre-established (acceptable) Fractogram area, and FA is the sample fractogram area. DFR is set by sending a 0-5 volt signal to the dilution valve. As DFR increases, the vented (Y) eluant flow rate decreases.

其中DFR為稀釋劑流量，C為常數(shù)，PA為預(yù)先設(shè)定的(可接受的)分形圖面積，F(xiàn)A為樣品分形圖面積。DFR是通過(guò)向稀釋閥發(fā)送0-5伏信號(hào)來(lái)設(shè)置的。隨著DFR的增大，流出(Y)淋洗液流量減小。

PSD data files are saved to a network location. A Honeywell PlantScape process control system reads the PSD data and performs process control steps such as valve opening/closing and reactor temperature adjustment.

PSD數(shù)據(jù)文件保存到網(wǎng)絡(luò)位置?；裟犴f爾PlantScape過(guò)程控制系統(tǒng)讀取PSD數(shù)據(jù)并執(zhí)行過(guò)程控制步驟，如閥門打開(kāi)/關(guān)閉和反應(yīng)堆溫度調(diào)節(jié)。

Figures 11 and 12 show polyvinyl acetate CHDF data collected from an on-line device connected to a batch reactor.

圖11和圖12顯示了從連接到間歇式反應(yīng)器的在線設(shè)備上收集到的聚醋酸乙烯CHDF數(shù)據(jù)。

Figure 11. On-line CHDF UV-detector output for a PVA latex from a batch reactor.

圖11-聚乙烯醇乳膠在一批反應(yīng)器在線CHDF紫外檢測(cè)器輸出數(shù)據(jù)

Figure 12. On-line CHDF PSD data for PVA latex from a batch reactor.

圖12- 聚乙烯醇乳膠在一批反應(yīng)器在線CHDF PSD檢測(cè)器輸出數(shù)據(jù)

Conclusions：

結(jié)論：

CHDF particle size fractionation can be used for high-resolution particle size analysis of dispersions in the particle size range of 2 nm to 5 microns. A process on-line particle sizer has been implemented based on CHDF fractionation. This on-line device is capable of performing automatic sample dilution, and interfacing with a Honeywell Plant Control system.

毛細(xì)管流體分離(CHDF)粒度分離技術(shù)可用于2nm ~ 5μm范圍內(nèi)的分散體的高分辨率粒度分析。在毛細(xì)管流體分離(CHDF)的基礎(chǔ)上，實(shí)現(xiàn)了一種工藝在線粒度儀。該在線裝置能夠自動(dòng)稀釋樣品，并與霍尼韋爾工廠控制系統(tǒng)接口。

Acknowledgements：

致謝：
The author would like to thank Dr. Tim Crowley for sharing some of the CHDF on-line data presented here.

作者要感謝Tim Crowley博士與我們分享CHDF在線數(shù)據(jù)。

References：

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