<p>The invention relates to a differential mobility analyser (DMA) which is used to obtain the electric field conditions necessary for it to have a component that is opposed to the drag flow. As a result of the component of the electric field that is opposed to the drag flow, the main electric field is not perpendicular to the velocity field of the drag flow but oblique thereto. Under these conditions it is possible to increase the resolution of the device, thereby reducing the error threshold in the detection of the type of particle injected into the analyser. The invention is characterised by the arrangement and type of electrodes used to obtain the oblique electric field. The invention also includes the use of the analyser as part of a device used to produce an assembly that combines the efficiency of the prior art analyser with the high resolution of the inventive analyser.</p>
