Abstract
The counts of microspheres in 20 testing solutions were determined using 2 Coulter Counters (electrical resistance) and 2 HIAC/Royco (light blockage) particle analysers. The mean cumulative number of microspheres (≥2μm) in unit volume of the solutions determined using the Coulter Counters was higher than those determined by HIAC/Royco particle analysers. The mean cumulative counts obtained by the two Coulter Counters are similar; however, t-test analysis shows significant difference for the counts of 8 different types of solutions. The mean cumulative counts obtained by the two HIAC/Royco Counters varied greatly and t-test analysis showed that 18 out of 20 of the solutions gave significant difference