MEASURING SIZE DISTRIBUTION OF ORGANIC AND INORGANIC CRYSTALS OFDIFFERENT SHAPES USING DIFFERENT TECHNOLOGIES

摘要

The ultrasonic attenuation (UA) technique was developed to measure not onlyparticle size distribution (PSD) but also concentration for on-line and off-line analysis ofhigh concentration dispersions. Another significant characteristic along with particle size isparticle shape. Particle shape influences the apparent particle size as measured byvarious instruments. Currently, acquiring particle size along with shape measurement isnot readily achieved. Image analysis measures shape with size distribution but only forvery small samples, not generally practical for the process industries. Shape factors havebeen calculated from microscopic images using conventional image analysis (IA)techniques. Particle sizing data measured by UA is more representative than by IAbecause much larger samples are used for analysis. In this paper, size distributionsobtained by ultrasonic attenuation (UA), laser diffraction (LD), focused beam reflectancemeasurement (FBRM) and image analysis (IA) are compared and the influence of crystalshape on size measurements is investigated.Data obtained from UA has been combined with information on shape factor fromimaging to obtain equivalent particle size distributions. Data obtained from LD have beenconverted with a shape factor (sphericity) from imaging to obtain true Crystal sizedistribution (CSD). In a previous study [1], the influence of shape on size measurementhas been investigated using different sizing techniques for non-fragile materials. Theseparticles showed significant variation in measured PSD with their different shapes. In thispaper, the same phenomenon was observed with evolving polymorphs of L-glutamatecrystals ( α and β form) and non-polymorphic oxalic acid and copper sulphate.