Disclosed is a method for the measurement of the mass and/or charge of a charged particle. The method involves injecting the particle into a sampling device made up of a tube comprising a Faraday cage with a region of a grounded conductive material on either end of it. The particle flows through the tube in a stream of gas and as it passes through the Faraday cage it induces a charge on the cage wall. By measuring the magnitude of the induced charge or its duration in the cage, the magnitude of the charge on the particle or the mass of the particle can be determined.