The localized potential gradients created by a microplasma are capable of trapping and concentrating micro- and nanoparticles. In this paper, argon microplasma is generated within a 350-mum discharge gap formed within a microstrip transmission line. Melamine formaldehyde particles (1 mum) are released approximately 2 cm away from the microplasma. The microparticles are then negatively charged by stray electrons, electrostatically drawn toward the potential well of the microplasma, and trapped within the microplasma. The particles are observed to form Coulomb crystals. Time-of-flight experiments show that the particles are trapped in the microplasma by balancing the electrostatic force of the potential well against the molecular drag force. Pulsed plasma data show that the particles retain a net negative charge after the plasma has been extinguished, allowing detection and sorting by electrostatic methods.