Electro-optical sensing device with reference channel

A method for detecting an analyte of interest in a medium, said method comprising:

• a. providing an electro-optical sensing device containing a first and a second indicator elements each containing indicator molecules having an optical characteristic responsive to the presence of an analyte and positioned to receive excitation radiation from a radiation source and to transmit resultant radiation to a pair of photosensitive elements, and wherein said first indicator element is covered by a cover having at least one bore therethrough and said second indicator element is covered by an analyte-impermeable, hermetically-sealed chamber that renders the second indicator element insensitive to the presence of the analyte in the medium external to the device;
• b. introducing a medium to contact said first indicator element through the bore in said cover;
• c. activating said radiation source to emit radiation to said first and second indicator elements, and optically detecting an optical response of said first and second indicator elements;
• and
• d. evaluating said response to determine the presence or concentration of at least one analyte of interest in the sample, wherein said response detected from said second indicator element is used as a reference to cancel variables that affect both said first and second indicator elements.