Method For Particle Size Measurement Research Articles

Particle Size Measurement Using Dynamic Light Scattering at Ultra-Low Concentration Accounting for Particle Number Fluctuations.

Dynamic light scattering (DLS) is a popular method of particle size measurement, but at ultra-low particle concentrations, the occurrence of number concentration fluctuations limits the use of the technique. Number fluctuations add a non-Gaussian term to the scattered light intensity autocorrelation function (ACF). This leads to an inaccurate particle size distribution (PSD) being recovered if the normal DLS analysis model is used. We propose two methods for inverting the DLS data and recovering the PSDs when number fluctuations are apparent. One is to directly establish the relationship between the non-Gaussian ACF and the PSD by the kernel function reconstruction (KFR) method while including the non-Gaussian term to recover the PSD. The other is to remove the effect of the non-Gaussian term in the ACF by the baseline reset (BR) method. By including the number fluctuation term, the ideal recovered PSD can be obtained from the simulated data, but this will not happen in the experimental measurement data. This is because the measured intensity ACF contains more noise than the simulated ACF at ultra-low concentration. In particular, the baseline noise at the tail of long delay time of ACF overwhelms the number fluctuation term, making it difficult to recover reliable PSD data. Resetting the baseline can effectively remove the digital fluctuation term in ACF, which is also a feasible method to improve PSD recovery under ultra-low concentration. However, increasing noise at ultra-low concentrations can lead to errors in determining an effective baseline. This greatly reduces the accuracy of inversion results. Results from simulated and measured ACF data show that, for both methods, noise on the ACF limits reliable PSD recovery.

Precise measurement of particle size in colloid system based on the development of multiple-angle dynamic light scattering apparatus

Dynamic light scattering (DLS) is a widely used, non-invasive and in-situ method for particle size measurement. However, the precision of the measurement results is still under discussion. Theoretically, the apparent hydrodynamic diameter measured by DLS varies with scattering angle due to Mie scattering as well as long-distance interaction between particles. In this paper, a multiple-angle dynamic light scattering (MDLS) apparatus is established. After determining the critical concentration at which multiple scattering occurs at different scattering angle, polystyrene latex (PSL) particles sized from 23 to 500 nm diluted with different concentrations are precisely measured at different scattering angles. By introducing special pin-holes, precise alignment design and beam-stops at all scattering angles, the precision of the MDLS apparatus is highly improved. DLS results are strongly angular and concentration dependent, and the trends vary with particle size. DLS results at infinite dilution and zero angle are obtained after extrapolation, which eliminates the effects of long-range interactions and intraparticle interference. The present optical design extends the application validity of this method from nano particle to submicron particle.

Machine learning holography for measuring 3D particle distribution

We propose a learning-based image processing method for particle size measurement based on digital holography in this paper. The proposed approach uses a modified U-net architecture with recorded holograms, hologram reconstructed to each longitudinal location, and minimum intensity projection in longitudinal direction as inputs to produce outputs consisting of in-focus particles at each longitudinal location and their 2D centroids. A soft generalized dice loss is used for the particle size channel and a total variation regularized mean squared error loss is employed for the 2D centroids channel. The proposed method has been assessed using synthetic, manually-labeled experimental, and real experimental holograms. The results demonstrate that our approach have better performance in comparison to the state-of-the-art non-machine-learning methods in terms of particle extraction rate and positioning accuracy. Our learning-based approach can be readily extended to other types of image-based particle size measurement tasks such as shadowgraph imaging and defocusing imaging.

Light-Scattering Sizing of Single Submicron Particles by High-Sensitivity Flow Cytometry.

Rapid and reliable size measurement of single submicron particles (100-1000 nm) is important for quality control of particulate matter, biomedical research, environmental study, and drug delivery system development. Though direct measurement of the elastically scattered light from individual submicron particles represents the simplest method for particle size measurement, the inadequate instrument sensitivity and complicated relationship between scattering intensity and particle size render it a great challenge. Combining the superior sensitivity of a laboratory-built high-sensitivity flow cytometer (HSFCM) in the side scattering (SSC) detection of single nanoparticles and the great efforts in synthesizing 38 highly monodisperse silica spheres ranging from 180 to 880 nm with small size intervals, here we report the first comprehensive comparison between the experimentally measured and Mie theory calculated intensities of light scattered by single submicron particles. Good agreements were observed for both the silica spheres and polystyrene beads at both the perpendicular and the parallel polarizations of the incident laser beam. Compared with perpendicular polarization, parallel polarization can resolve differently sized beads better due to the continuously increased scattering intensity with particle size. The predictive capability of the simple numerical model constructed in present work can be exploited to allow us to foresee scattering behavior on flow cytometers. More importantly, the linear correlation between the measured and the calculated scattering intensities enables us to develop a method that can measure the particle size of submicron particles with the precision and accuracy of Mie theory rather than a calibration curve fitted by several sparsely separated size reference standards. Comparable sizing resolution and accuracy to those of electron microscopy were demonstrated for Gram-positive bacteria Staphylococcus aureus. The as-developed method shows great potential in guiding the accurate size measurement of submicron particles.

A study on the applicability of in-line measurements in the monitoring of the pellet coating process

Special populations including paediatric and elderly patients often need advanced approaches in treatment, such as one-a-day dosing, which is achieved with modified release formulations or alternative routes of applications such as nasogastric route. Pellets are a dosage form that is frequently used in such formulations.The aim of the present work was to study the applicability of two in-line techniques, namely, Near Infrared Spectroscopy (NIR) and Spatial Filtering Technique (SFT) in the pellet coating process. The first objective of our work was to develop a prediction model for moisture content determination with the in-line NIR and to test its robustness in terms of sensitivity to changes in composition of the pellets and performance in wide range of moisture content. Secondly, the in-line SFT measurement was correlated with different off-line particle size methods. The third objective was to evaluate the ability of both in-line techniques for the detection of undesired deviations during the process, such as pellet attrition and agglomeration. Finally, the ability to predict coating thickness with the in-line NIR probe was evaluated.Results suggested that NIR prediction model for moisture content was less robust outside the calibration range and was also sensitive to changes in composition of the film coating. Nevertheless, satisfactory prediction was achieved in the case when coating composition was partially altered and adequate calibration range was used. The SFT probe results were in good correlation with off-line particle size measurement methods and proved to be an effective tool for coating thickness determination during the coating, however, the probe failed to accurately show the actual amount of the agglomerates formed during the process. In experiment when pellet attrition was initiated, both probes successfully detected abrasion of the pellet surface in real time. Furthermore, a predictive NIR model for coating thickness was made and showed a good potential to measure coating thickness in-line, suggesting that the NIR probe can be used as a single tool to monitor water content, coating thickness, and deviations in the coating process.

Effect of scattering angle error on particle size determination by multiangle dynamic light scattering.

Dynamic light scattering (DLS) is a popular method of particle size measurement. Multiangle dynamic light scattering (MDLS) collects DLS data at multiple angles and analyzes the data simultaneously to improve the particle size measurement. Using data from several scattering angles admits the possibility of introducing noise caused by scattering angle error in the measurement, which may have an impact on the performance of the MDLS technique. We investigate the effect of scattering angle noise on recovered particle size distributions (PSDs) using simulated and measured MDLS data and various levels of angular noise. Our results show that, for unimodal PSDs, those with small particle sizes are more strongly affected by the noise than are medium and large particle size systems. For bimodal PSDs, those containing small-sized particles are also more affected by the noise than the systems of larger particles. Furthermore, broad PSDs are more vulnerable to angular noise than narrow PSDs.

A method to determine particle size distribution in soils with gypsum

Gypseous (>40% gypsum) and gypsiferous (1 to 40% gypsum) soils are estimated to comprise from 100million to 200millionha globally including over 1millionha in the U.S. More intensive land use on these soils has resulted in greater demand for information on distribution, properties, and behavior of these soils. Common laboratory methods for determining particle size distribution of soils involve pretreatment to remove gypsum and more soluble salts since they interfere with sample dispersion and establishment of a stable clay suspension. Thus, particle size measurements using standard methods with pretreatment to remove gypsum only reflect the size distribution of essentially insoluble, dominantly silicate minerals, and do not reflect the size distribution of the whole soil including gypsum. Forcing results into a silicate–mineral basis in moderate to high gypsum soils can profoundly distort analytical results. The objective of this project was to develop and evaluate an alternative method of particle size measurement for soils with gypsum that includes size distribution of gypsum particles. Three disaggregation methods for estimation of total sand and sand separates were evaluated: 1) drying sieving, 2) shaking in a 7:3 ethanol:water solution, and 3) sonication in a 7:3 ethanol:water solution. Evaluation of samples with and without gypsum indicated that the sonication method was the most effective for disaggregation as indicated by sand fraction distribution and microscopic grain evaluations. Application of the method to samples from three gypseous pedons yielded grain-size distributions that better agreed with hand textural class estimates than conventional grain-size analysis by standard methods that included pretreatment to remove gypsum. Comparison of CEC/clay and 1500kPa water/clay ratios for the samples between the two methods also suggested that the proposed method yielded clay contents more consistent with other property data for the same horizons. Improved particle size evaluations for soils containing gypsum, especially those with high gypsum contents, will improve the understanding and ability to interpret and predict behavior of these unique soils.

Review on Rice Flour Manufacturing and Utilization

Background: The Korean government launched a project in 2008, where the amount of rice used as raw ingredient in rice-based foods in 2012 was planned to increase up to 10% (470,000 ton) of the total rice production through developing various new rice-based processed foods and their commercial manufacturing technology. Among the four major rice-based processed foods, rice cakes and noodles need rice flour as their main raw ingredient. Technology in rice flour utilization and manufacturing is far behind than the technology pertinent to wheat flour in many subject areas. Purpose: This review aims to provide information on rice flour utilization and manufacturing with some fundamental subjects in the area of size reduction. Results: A variety of food items including bread, noodle, cake, cookie, muffin, pre-mix, beverage, vinegar, surimi, and artificial meat have found rice flour as their raw ingredient. Rice bread made out of 100% rice flour has been developed and is now sold in retail stores. Various noodle products made from rice flour are also on the market. Issues on product definition and labeling regulation about rice flour content of the products were explored. Generalized grinding equations available in the literature were seldom used in practice; instead, it has been a general practice to develop empirical equations from test milling data. Introductory remarks on three popular particle size measurement methods (sieving, Coulter counter, light diffraction) were explained. Mathematical expressions frequently used to describe particle size distribution and to correlate cumulative quantity of particles with particle size were represented. Milling methods used in producing rice flour were described along with their advantages and disadvantages. Because of their profound effect on functional properties of the rice flour, four rice flour milling equipments used at both laboratory experiments and commercial manufacturing plants were discussed.

Particle analysis based on light scattering of particles illuminated by a divergent Gaussian beam

Light scattering by particles located in a divergent beam is developed recently as a new method for particle size measurement, which has the characteristics of broadening the range of measurable particle sizes and reducing the requirements for experimental equipment system. In this paper, a theoretical model is presented which takes into account the refraction of the light while passing across the interfaces of the media. Analytical expression, based on the ray propagation, is deduced to describe the scattered light distribution on the detector. In the experimental parts, particle size distributions are extracted from the measurements by using the inverse algorithm. The experimental evidence shows that all the measurements give reasonable results on the particle size distribution. The results are insensitive to the parameters of the optical arrangement.

Application of Genetic Algorithms in Particle Inversion

In the general light scattering particle size measurement methods, the inversion error of results is nonuniform distribution. To solve this problem, genetic algorithms based on real number coding were proposed to be applied in the inversion of particle size distribution. In this method, the fitness function was further improved in order to reduce the individual error, it not only considered sum of all errors but also took into account the individual maximum error. With this improved fitness function, the error distribution is homogenized. The light spectrum about measurement and calculation are basic entirely fitting. The results show that the algorithm is accurate and reliable.

Sedimentation field flow fractionation monitoring of bimodal wheat starch amylolysis

Enzymatic starch granule hydrolysis is one of the most important reactions in many industrial processes. In this study, we investigated the capacity of sedimentation field flow fractionation (SdFFF) to monitor the amylolysis of a bimodal starch population: native wheat starch. Results demonstrated a correlation between fractogram changes and enzymatic hydrolysis. Furthermore, SdFFF was used to sort sub-populations which enhanced the study of granule size distribution changes occurring during amylolysis. These results show the interest in coupling SdFFF with particle size measurement methods to study complex starch size/density modifications associated to hydrolysis. These results suggested different applications such as the association of SdFFF with structural investigations to better understand the specific mechanisms of amylolysis or starch granule structure.

Characterization of particle sizes in bulk pharmaceutical solids using digital image information.

The purpose of this study was to demonstrate a novel method of extracting relevant information from undispersed bulk powder surfaces to be used in particle size analysis. A new surface imaging approach for undispersed powders combined with multivariate modeling was used. Digital surface images of various granule batches were captured using an inventive optical setup in controlled illumination conditions. A descriptor, the gray scale difference matrix (GSDM), which describes the particle size of granular material was generated and extracted from the powder surface image information. Partial least squares (PLS) modeling was used to create a model between the GSDM and the particle size distribution of granules measured with sieving. The use of lateral illumination and the combining of information from 2 surface images strengthened the shading effects on the powder surfaces. The shading effects exposed the topography or the visual texture of the powder surfaces. This textural information was efficiently extracted using the GSDM descriptor. The goodness-of-fit (R2) for the created PLS model was 0.91 and the predicted variation (Q2) was 0.87, indicating a good model. The model covered granule sizes in the size range of approximately 20 to 2500 microm. The extracted descriptor was effectively used in particle size measurement. This study confirms that digital images taken from undispersed bulk powder surfaces contain substantial information needed for particle size distribution analysis. The use of the GSDM enabled the utilization of bulk powder surface information and provided a fast method for particle size measurement.

Laser method for particle size measurement

A method functionally compatible with laser Doppler anemometry is proposed for particle size measurement. This method is based on determination, in real time, of the correlation function of the direct and inverted images of a particle in scattered light. The image is inverted along an axis which is optically conjugate to the direction of the fringe vector of the probe interference field in a laser anemometer.

A Theoretical and Experimental Study of the Total Light Scattering Technique for particle size analysis

AbstractThe total light scattering method for particle size measurement has a series of outstanding features, e.g. very simple instrumental arrangement, no serious requirements for its optical, photodetecting and electronic systems and its ease of use. Nevertheless, some problems still remain unsolved which should be dealt with to improve its further applications. An improvement has been made in this work. Comprehensive theoretical studies showed that this method is applicable to particle size analysis in the range 0.1–10 μm, i.e. for those particles whose diameter lies between the lower limit of the diffraction method and the upper limit of photon correlation spectroscopic (PCS) technique. Experimental studies with different monodisperse polystyrene latex spheres as standard reference material give good agreement with their nominal values.

A Comparison of Image Analysis With Other Methods of particle size measurement for general purpose PVC resins

AbstractOf all methods of particle size analysis determination only microscopy and subsequent image analysis enables accurate, geometrically determined size parameters to be measured. For this reason image analysis is a convenient referee or umpire method against which to compare other techniques.In this study, a series of seven poly(vinyl) chloride (PVC) resins were characterized by optical microscopy and image analysis, sieves, HIAC and Coulter counter. It was not found possible to perform the image analysis measurements without operator intervention with a light pen to separate agglomerates. The PVC particles were far too irregular to enable this task to be performed by erosion and dialation techniques. The errors at 90% confidence associated with the image analysis study were: calibration ± 1.7%, counting statistics ± 1% (max) with a focus and algorithms error which ranged from ½‐3% depending upon the quantity being measured. These numbers gave a total error of ± 2% (ca. one pixel) for equivalent circular diameter (ECD) and ± 4% (ca. two pixels) for object breadth. In general the agreement between the various techniques was quite good suggesting that the object breadth (OB) as measured by sieves was nearly identical to equivalent spherical diameter (ECD) as measured by the HIAC and Coulter counter for the samples investigates.A study of the image analysis data alone confirmed that OB and ECD were nearly identical with ECD running about 6.1 m̈m above OB.Mass resin samples, which are prone to electrostatic charging effects, tended to give slightly higher results in those methods which measured the resin in the dry state (HIAC and sieves). Finally, it should be suggested that many of the classical concepts of resolution and depth of focus which are used to place limits upon the performance of the optical microscope do not necessarily apply to particle size determination by image analysis. If the chord through the particle which describes its diameter can be considered an approximation to a square wave then it is the fundamental frequency of the Fourier components of that square wave that contains the size information. This should be true for microscopic objects which are absorbing of light and non‐retarding in nature.Once this fundamental frequency can be identified then sizing accuracy is dependent chiefly on the signal to noise ratio of the system.

Critical Review of Particle Size Analysis

A considerable range of equipment exists for particle characterization. The author restricts his survey to recent developments in methods of particle size measurement in the areas of sieving, sedimentation equipment, centrifugal techniques, and light scattering and light attenuation methods. Further sources of information are suggested for aspects of the subject which, for reasons of time and space, could not be considered in the present paper. PM/0225

Particle Size Measurement of Fine Powder with Sieving

A convenient method of particle size measurement by using Micro-sieve for fine powder is proposed here. The sieving eqipment for measurement consists of ultrasonic vibrator, electromagnetic vibrator, and reciprocating pump by which pressure and vacuum is applied to Micro-sieve. The sieving rate and the particle separation is accelerated by both vibrations, and the reciprocating pump prevents particles from precipitating on the sieves.In this report reasonable sieving conditions and the measured examples of particle size distribution were described. Results are compared with those obtained by some other methods.This sieving equipment is relatively cheap. Results are reproducible and the operation is simple.

Particle- and grain-size measurement by x-ray fluorescence

A method of particle size measurement is presented which is based on the fact that the intensity of fluorescent X-rays from an element in a particle is dependent on particle size. The effect can be expressed by the intensity ratio R, the ratio of the intensity from a sample containing particles of size S to the intensity from a sample containing particles of zero size, both samples having the same concentration of the fluorescing element. An equation relating R and S was derived for low concentrations of cubic particles suspended in a matrix material. The equation predicts that R will depend only on the particle size S, the sample thickness, and the linear absorption coefficients of the particle and matrix materials. Experiments were conducted using closely-sized fractions of W, Cu, and bronze powders in various matrices. It was found that by varying the incident X-rays, the matrix material and the fluorescent X-rays, the sensitivity of R to different ranges of particle size can be controlled. R was found to decrease with particle concentration and small deviations in linearity were found for mixtures of particle sizes. The experimental results were in fair agreement with the equation. The method is rapid and non-destructive, requires only a small amount of sample and permits measurement of the sizes of different particle species in a single sample. It appears to be particularly attractive for rapid, routine measurements of average particle size on many commercial powders as well as for grain size measurement on alloy and rock samples. It appears possible to use the method for on-stream particle size measurement of suspensions.