A new sampling system, the in vitro electrostatic collector, was developed to collect ambient particles for in vitro studies. The system consists of two units: first, particles are concentrated by means of the versatile aerosol concentration enrichment system (VACES), and subsequently they are drawn through an electrostatic precipitator (ESP). The particle sample is collected on a petri dish that contains cell cultures, or on any other desirable substrate suitable for particle collection and analysis. The VACES makes it possible to sample for short time intervals, which favors cell viability and exposure characterization. The laboratory tests showed that collection efficiency under optimized conditions is higher than 95% across all particle diameters measured (18 nm to 3.0 mu m), regardless of aerosol type. The field experiments showed that the VACES with a tandem-virtual impactor system is capable of concentrating ambient ultrafine, accumulation and coarse particles by 80-100 times. The in vitro electrostatic collector has the potential to perform hourly direct, solvent-free PM collections for toxicological studies. (C) 2007 Elsevier Ltd. All rights reserved.