Abstract: A sensor comprises a sensor housing, having a channel; a porous substrate, in the channel; an analysis chemistry reagent, on the porous substrate; and a nozzle, in fluid connection with the channel. The porous substrate fills a cross section of the channel, and the cross-sectional area of the channel at the porous substrate is greater than the cross-sectional area at the nozzle.

Abstract: A fluorimetric system, apparatus and method are disclosed to measure an analyte concentration in a sample. A sensor reagent housing is also disclosed which comprises a channel and a porous medium having an analysis chemistry reagent, such as a nucleic acid analysis chemistry reagent. The apparatus and system are portable for field use, with an apparatus housing having a size adapted to fit into a user's hand. An apparatus also includes a sensing chamber and cover, a user interface, a light source, a photomultiplier tube, an amplifier, an A/D converter, a memory, and a processor. In various embodiments, the processor performs a data fitting, determines a sample reaction rate parameter, and determines the analyte concentration from a comparison of the sample reaction rate parameter with stored calibration data. The processor may also generate the calibration data and site-specific offset factors, and modify the calibration data using an offset factor.