A field testing device is provided for quantitating psychoactive components of marijuana such as THC in biological fluids such as saliva. Such a device may include an HPTLC plate for separating interferents from THC and may also include fluorometric components for quantitating THC. The device may include a microprocessor adapted to relate fluorescent intensity to analyte concentration through one or more calibration curves. Devices may optionally include microfluidics for carrying out HPTLC on biological samples including sample reservoirs, reagent reservoirs, micro-pumps, mixers, and the like.
