Electrokinetic devices and methods are described with the purpose of collecting assayable agents from a dielectric fluid medium. Electrokinetic flow may be induced by the use of plasma generation at high voltage electrodes and consequent transport of charged particles in an electric voltage gradient. Actively growing mold releases the carbohydrate cell wall component (1→3)-β-D-Glucan into the air. The invention recognizes that the airborne fraction is that which affects respiratory health and selectively tests for a free form which is soluble in aqueous medium. The sample to be analysed is preferably collected by the electrokinetic propulsion method described, but any air sampling method such as filtration, impactor or impingement may be applicable.