High-sensitivity method for counting low concentrations of particles in liquids using centrifugation and image analysis

new method was developed for counting low concentrations of particles suspe nded in a liquid, and found to be limited only by Poisson statistics. The m ethod, called the image cytometry-centrifugation (ICC) method, uses centrif ugation to concentrate particles into a narrow observation area at the bott om of a specially designed cuvette, and then uses image analysis to measure the number of particles. Our method was used to count from 1 to 64 fluores cent beads suspended in 500 mu l of liquid. By comparing the number of coun ted beads with the actual number of beads added to the liquid, we confirmed that the counting accuracy of the ICC method is limited by Poisson countin g statistics.