ANALYTICAL SPLITT FRACTIONATION - RAPID PARTICLE-SIZE ANALYSIS AND MEASUREMENT OF OVERSIZED PARTICLES

In SPLITT fractionation (SF), particles or molecules are separated rapidly by field-driven migration over a short (submillimeter) path lying across a ribbonlike flow cell having splitters at the ends. The outlet splitter separates components of high and low mobilities, directing the fractions to different outlet substreams for collection and measurement. The SF process, when run continuously, allows the scaleup of difficult separations. However, the rapid (often < 1 min) division and measurement of injected sample pulses can provide useful and timely analytical information. When used this way SF becomes analytical SPLITT fractionation (ASF). Here we utilize a miniature gravity SPLITT cell for particle size analysis in the 5-75-mum size range. The measurement of ''oversized'' particles is particularly straightforward using ASF. Oversized particles (those exceeding a criterion diameter) have adverse effects on the performance or safety of such products as abrasives, polishers, coatings, and pharmaceutical emulsions. Oversized particle analysis is illustrated using starch granules, abrasive particles, and glass beads. Most run times are 0.3-2.0 min. By making a series of runs at different cutoff diameters, we show that entire size distribution curves can be constructed. This case is illustrated using quartz particles and glass beads. By using microscopy and published size distribution data, we show that our results are in good agreement with those expected theoretically.