The Couette centrifugal particle mass analyzer (CPMA) classifies particles by their mass-to-charge ratio. Unlike the aerosol particle mass (APM) analyzer, the Couette CPMA uses a stable system of forces to improve the transfer function of the classifier. A prototype Couette CPMA has been built and tested. The experimental results from the prototype agree well with theory and it is found that indeed the transfer function of the Couette CPMA is better than the APM's. Experimental work is shown using a differential mobility analyzer (DMA) and Couette CPMA to classify polystyrene latex (PSL) and di-2-ethylhexyl sebacate (DEHS) particles. By measuring the mass of PSL particles the absolute uncertainty of the Couette CPMA was found to be 6.7-38% higher in terms of mass (or 2.2-11% higher in terms of equivalent diameter) than the expected value. However, when the DMA-CPMA system was calibrated with PSL particles the density of DEHS particles was measured to within approximately 3% of the expected value. (c) 2006 Elsevier Ltd. All rights reserved.