Capture and detection of microbes by membrane methods

A method of analyzing an analyte collected on a membrane comprising:

• passing a fluid sample across a membrane, wherein the fluid sample comprises an analyte that is at least partially retained by the membrane;
• adding a visualization agent to material collected on the membrane when the fluid sample is passed across the membrane;
• collecting an image of the collected material using white light, at a first wavelength of light, a second wavelength of light, and a third wavelength of light, wherein the analyte comprises a color corresponding to the first wavelength of light;
• forming a first mask corresponding to an image of the collected material at the second wavelength of light;
• forming a second mask corresponding to an image of the collected material at the third wavelength of light;
• subtracting the first mask and the second mask from the image of the collected material in white light.

A method of sensing an analyte in a fluid comprising:

• passing the fluid across a porous membrane configured to capture the analyte on the porous membrane;
• applying a visualization agent to the particles on the porous membrane;
• detecting an image of matter captured on the porous membrane with a detector at a plurality of wavelengths of light;
• detecting an image of matter captured on the porous membrane at a specific wavelength of light, wherein the specific wavelength of light represents light that is not indicative of the presence of the analyte.