Artefact peaks in particle size distributions measured by the electrical sensing zone (coulter counter) method

Abstract

Artefact peaks on the coarse side of particle size distributions measured via the electrical sensing zone (ESZ) technique for a series of copolymer latices have been examined. These artefacts result from particles entering the orifice mouth at the periphery. It is shown that the ‘volume’ shift of the artefact peak relative to the main or normal peak may be calculated from the equation ▪ where dφ/ dx is the axial component of the potential gradient across the mouth of the orifice, of radius R, at a radial distance r from the axis; α′ and β′ are constants with values of 0.0324 and 1.082 respectively. The relative modal heights of the artefact and main peaks are also accounted for. The occurrence of artefact peaks can introduce difficulties in the use of the ‘half-count’ method of calibration; a preferred alternative method involves identification of the modal value of the main peak in the measured ESZ size distribution of the reference material used for calibration.