Particle Size Distributions from Fraunhofer Diffraction

Generalized concepts of information theory indicate that the numerical solution of the Fredholm equation of the first kind relating a particlesize distribution to its Fraunhofer diffraction pattern can be achieved without ill-conditioning by use of a truncated eigenfunction expansion. We give explicit analytic formulae for the eigenfunctions and eigenvalues of this problem and give numerical values of the latter of use for experimental reductions. The results show how many independent fractions of a particle-size distribution may be determined in the presence of quantified levels of noise.     

Comparison of Particle Size Distributions Measured Using Different Techniques

In this article, particle size distributions (PSDs) measured by different techniques, including image analysis (IA), laser diffraction (LD), ultrasonic attenuation spectroscopy (UAS), and focused-beam reflectance measurement (FBRM), are compared for spherical glass beads and nonspherical silica flakes. It is shown that particle shape strongly affects the results obtained by different techniques. For spheres, the PSDs obtained by IA, LD, and UAS agree well. There is no consistent result among different particle measurement techniques for nonspherical particles. The conversion between PSDs obtained by IA, LD, and UAS has been based on particle shape factors. Caution must be exercised when a measured chord length distribution (CLD) is used to indicate the PSD during a process because the CLD result obtained by FBRM is complex, depending not only on the PSD, but also on particle optical properties and shape.     

Comparison of Particle Size Distributions Measured Using Different Techniques

ABSTRACT

In this article, particle size distributions (PSDs) measured by different techniques, including image analysis (IA), laser diffraction (LD), ultrasonic attenuation spectroscopy (UAS), and focused-beam reflectance measurement (FBRM), are compared for spherical glass beads and nonspherical silica flakes. It is shown that particle shape strongly affects the results obtained by different techniques. For spheres, the PSDs obtained by IA, LD, and UAS agree well. There is no consistent result among different particle measurement techniques for nonspherical particles. The conversion between PSDs obtained by IA, LD, and UAS has been based on particle shape factors. Caution must be exercised when a measured chord length distribution (CLD) is used to indicate the PSD during a process because the CLD result obtained by FBRM is complex, depending not only on the PSD, but also on particle optical properties and shape.     

Transformation of Chord Length Distributions into Particle Size Distributions Using Least Squares Techniques

ABSTRACT

For the characterization of particulate systems, various measuring techniques exist. Many of these assume that the particles are spherical in order to compute a particle size distribution (PSD) from the measured data. However, in many applications the shape of the particles deviates from a sphere, and as a consequence the computed PSD will contain errors because of this violated assumption. Measuring techniques that do not require this a priori assumption are, for example, those that measure the chord lengths of the particles. A disadvantage of the latter techniques is that the interpretation of the chord length distribution (CLD) is less transparent than the interpretation of a shape-based PSD (the PSD given an assumed particle shape). To facilitate the interpretation of a CLD, an algorithm based on least squares optimization techniques is presented. This algorithm computes the shape-based PSD that best explains the measured CLD and can, for example, discriminate spheres from rods using information of the CLD only. Knowledge about the type of PSD (e.g., Gaussian or log-normal) is not required.     

Transformation of Chord Length Distributions into Particle Size Distributions Using Least Squares Techniques

For the characterization of particulate systems, various measuring techniques exist. Many of these assume that the particles are spherical in order to compute a particle size distribution (PSD) from the measured data. However, in many applications the shape of the particles deviates from a sphere, and as a consequence the computed PSD will contain errors because of this violated assumption. Measuring techniques that do not require this a priori assumption are, for example, those that measure the chord lengths of the particles. A disadvantage of the latter techniques is that the interpretation of the chord length distribution (CLD) is less transparent than the interpretation of a shape-based PSD (the PSD given an assumed particle shape). To facilitate the interpretation of a CLD, an algorithm based on least squares optimization techniques is presented. This algorithm computes the shape-based PSD that best explains the measured CLD and can, for example, discriminate spheres from rods using information of the CLD only. Knowledge about the type of PSD (e.g., Gaussian or log-normal) is not required.     

Influence of Particle Size on the Distributions of Liposomes to Atherosclerotic Lesions in Mice

ABSTRACT

In order to confirm the efficacy of liposomes as a drug carrier for atherosclerotic therapy, the influence of particle size on the distribution of liposomes to atherosclerotic lesions in mice was investigated. In brief, liposomes of three different particle sizes (500, 200, and 70 nm) were prepared, and the uptake of liposomes by the macrophages and foam cells in vitro and the biodistributions of liposomes administered intravenously to atherogenic mice in vivo were examined. The uptake by the macrophages and foam cells increased with the increase in particle size. Although the elimination rate from the blood circulation and the hepatic and splenic distribution increased with the increase in particle size in atherogenic mice, the aortic distribution was independent of the particle size. The aortic distribution of 200 nm liposomes was the highest in comparison with the other sizes. Surprisingly, the aortic distribution of liposomes in vivo did not correspond with the uptake by macrophages and foam cells in vitro. These results suggest that there is an optimal size for the distribution of liposomes to atherosclerotic lesions.     

悬浮法成型UPR微粒的粒径及其分布

以不饱和聚酯(UPR)为原料,采用悬浮法制备粒径在120～250 μm的UPR微粒.考察了搅拌速度,油水比、分散剂及电解质对聚合物颗粒平均粒径及粒径分布的影响.     

一种单分散球形微粒的粒度表征

将一种用改进的液相沉淀法精心合成的单分散胶体二氧化硅球形颗粒样品 ,在不同的实验室 ,采用透射电镜(TEM )、盘式离心粒度仪和光子相关谱粒度仪等原理迥异的手段分别表征了其平均粒径 ,取得了非常一致的分析结果。这种样品有希望作为通用型的粒度标准。     

基于激光粒度仪测量油品喷雾粒径的方法研究

为了测量油品喷雾过程的雾化性能,通过对喷嘴雾化粒径的指标和雾化粒径测定方法的分析,利用激光粒度仪及粒径发生装置设计喷嘴雾化实验系统,并对实验系统的工作原理进行描述;在不同喷雾压力下测定煤基柴油特征平均粒径dv10、dv50、dv90、d[3,2]、d[4,3]数据。结果表明:柴油雾化过程分为形成阶段、扩散阶段、稳定阶段;喷雾压力越大,雾滴特征平均粒径dv10、dv50、dv90、d[3,2]、d[4,3]参数值越小,雾化效果越好,并且随着喷雾压力的增大,液滴雾化粒径减小的趋势变缓。     

小颗粒对粒度分析结果的影响

研究了水力分级过程中出现的小颗粒现象,由于表面能的作用,大颗粒容易吸附小的颗粒,从而造成团聚,在测定时由于强力超声的分散作用,将颗粒打散,从而在测试结果中出现了小颗粒现象.添加分散剂虽然可以改善小颗粒现象,但是也对分级产生不利的影响,导致分级后的粒度分布过宽,分散剂和超声的共同作用不但可以改善小颗粒现象,而且使分级后的粒度分布变窄.     

Particle Size Determination of a Three-Component Suspension Using a Laser-Scattering Particle Size Distribution Analyzer

In this study, a rapid and accurate particle size determination method using a light-scattering particle size analyzer was developed to measure the particle size and size distribution of a suspension containing three solid components: clotrimazole, triamcinolone, and sarafloxacin, which have different refractive indices. To ensure that data represent the size distribution of the primary particles of the suspension, the optimal sonication prior to and during measurement was detemined. It was found that the results obtained using the average relative refractive index (RRI) of the three components agreed with the results obtained using three individual RRIs. In addition, the results from two analysts demonstrated good reproducibility of this method. The size distribution data of the suspension were also compared to those of the bulk drugs. The results showed that the median particle size of this three-component suspension is relatively close to that of clotrimazole, which accounts for 80% of solid particles in the suspension. Furthermore, the results obtained using the light-scattering technique were comparable to those obtained using a polarized light microscope equipped with an image analyzer, indicating acceptable accuracy of this technique.     

粉体粒度与研磨技术

概括介绍了最常见的几种粉体粒度的测试方法 ,初步探讨了在超细粉碎过程中的逆研磨问题以及研磨条件 (分散介质、分散剂 )对研磨效率的影响。     

乙草胺微囊悬浮剂的粒度及其分布

采用原位聚合脲醛树脂法制备乙草胺微囊悬浮剂,利用激光粒度仪、光学显微镜、扫描电子显微镜等研究剪切速率、芯材黏度及固化阶段搅拌速率等对乙草胺微囊悬浮剂粒度分布的影响。结果表明:乳化过程中,控制剪切速率不变,通过添加质量分数为6.25%的甲苯可以有效减小乳液的粒度;在固化阶段,选择600 r/min的搅拌速率能够减少微囊之间的粘连与破囊现象。     

Production of Narrow Size Distributions in Classifier Mills

ABSTRACT

In various technical processes particles with well-defined, narrow size distributions are required. These powders can be produced in impact mills with internal classifier. The top size and size distribution of particles are controlled by variation of impact speed, and by the circumferential velocity of the impeller wheel classifier. Possibilities for minimization of the amount of fines are discussed. However, the production of a certain amount of fines is unavoidable. The physical limit of produced fines depends on the material properties and the parameters governing the impact of particles. The amount of unavoidable fines can be evaluated by means of single impact experiments, in which the particles are stressed with well-defined impact speed and angle of impact.     

颗粒联测的小结与思考

概述了2005年以前的颗粒联测活动情况,并对联测数据提出了4点思考.     

Nitrofurantoin: Particle Size and Dissolution

Tablets manufactured from micronized anhydrous nitrofurantoin exhibited unsatisfactory dissolution properties, whereas excellent results were obtained with unmilled drug material having fine particle size.