A system and method employing a microplasma to electrically charge nano- or micro-particles in a gas phase and, subsequently, trap the charged particles within the microplasma using the microplasma's built-in electric fields are disclosed. Confinement of the particles allows their density to be increased over time such that very low concentrations of particles can be detected, e.g., by methods such as laser scattering and/or detection of the plasma-induced charge on the particles. Preferably, charge detection methods are employed when nano-particles are to be trapped and detected.