Abstract: A method, system and kit for detecting the presence of an analyte includes placing a solution containing the analyte in a microcapillary tube and placing the microcapillary tube in contact with a layer of sorbent material so that the solution is withdrawn from the microcapillary tube by capillary action. A detector reagent which has been pre-deposited on the sorbent material indicates the presence of the analyte. The sorbent material, detector reagent, and the solvent for the analyte solution are selected so that the solvent is absorbed into the sorbent material and the analyte is adsorbed by the sorbent material and concentrated at the spot where the detector reagent has been pre-deposited and where the microcapillary tube contacts the sorbent material.