High-Sensitivity Method for Counting Low Concentrations of Particles in Liquids Using Centrifugation and Image Analysis

A new method was developed for counting low concentrations of particles suspended in a liquid, and found to be limited only by Poisson statistics. The method, called the image cytometry-centrifugation (ICC) method, uses centrifugation to concentrate particles into a narrow observation area at the bottom 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 fluorescent beads suspended in 500 µl of liquid. By comparing the number of counted 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 counting statistics.