A portable device for detecting an analyte associated with a target organic molecule in a liquid and/or solid substance. The device includes a test chamber, a probe, and a sensor. The test chamber contains a liquid volume of test solution including an analytical reagent selected to react with the analyte. The test chamber is sealed by a pierceable membrane wall. The probe is removably positionable to pierce the membrane wall to deposit a sample in the test chamber to form a test mixture with the test solution. The sensor is positioned to detect one or more characteristics of the test mixture in the test chamber indicative of a reaction between the analyte and the analytical reagent.