Abstract: A method and apparatus for analysing very low concentrations of particles present in a fluid sample. The apparatus comprises a support (1) defining and fluid flow channel (9) and a dual electrode array comprising a first electrode means (2) and a second electrode means (3). The first electrode means (2) is energised with an AC voltage of predetermined frequency to attract a predetermined type of particle to the electrode. The voltage is then switched off after a period of time and the second electrode means (3) is energised with an AC voltage of predetermined frequency. After a period of time the voltage is switched off, releasing the particles from the second electrode means for subsequent collection and/or enumeration.