Electro-optical sensing device with reference channel
View Patent ↗An electro-optical sensing device for detecting the presence and concentration of an analyte in a liquid or gaseous medium includes a pair of indicator elements positioned to receive radiation from a radiation source and transmit radiation to a pair of photosensitive elements. The indicator elements each contain indicator molecules having an optical characteristic responsive to the presence of an analyte; however, one of the indicator elements is covered by an analyte-impermeable chamber that renders the indicator element insensitive to the presence of the analyte in the medium outside the chamber so that it can be used as a reference to cancel environmental and systemic variables that affect both indicator elements. The chamber preferably holds an analyte-containing fluid in contact with the reference indicator element so that the indicator elements operate under nominally identical conditions. The indicator element used to measure the analyte in the external medium is preferably also covered, but in a manner that provides direct contact between the analyte and the indicator element.
1. An electro-optical sensing device for detecting the presence of an analyte in a medium, said sensing device comprising:
a. a radiation source that emits radiation;
b. a first and a second photosensitive elements configured to receive radiation and output an electrical signal in response thereto;
c. a first and a second indicator elements positioned to receive radiation from the radiation source and to transmit radiation to said first and second photosensitive elements, said first and second indicator elements each containing indicator molecules with an optical characteristic responsive to the presence of an analyte; and
d. a hermetically-sealed chamber covering said second indicator element so as to render said second indicator element insensitive to the presence of the analyte in a medium external to the device,
wherein said first indicator element is in fluid communication with said external medium and said second indicator element is not in fluid communication with said external medium, and
wherein said hermetically-sealed chamber contains an analyte-containing fluid in contact with said second indicator element.
2. The sensing device of claim 1 , further comprising a housing, wherein said first and second indicator elements, said first and second photosensitive elements, and said radiation source are mounted in said housing.
3. The sensing device of claim 1 , further comprising an analyte-impermeable cover mounted on the housing which defines at least a portion of the chamber covering the second indicator element.
4. The sensing device of clam 1 , further comprising an analyte-permeable cover mounted on the housing over the first indicator element.
5. The sensing device of claim 4 , wherein said analyte-permeable cover includes a bore formed therethrough to provide fluid communication between the first indicator element and the external medium.
6. The sensing device of claim 1 , wherein said first indicator element and said first photosensitive comprise a signal channel, and wherein said second indicator element and said second photosensitive element comprise a reference channel.
7. The sensing device of claim 1 , wherein said analyte-containing fluid is a liquid.
8. The sensing device of claim 1 , wherein said analyte-containing fluid is a gas.
9. The sensing device of claim 1 , wherein an analyte in said analyte-containing fluid is the same type of analyte to be detected in the external medium.
10. The sensing device of claim 1 , wherein an analyte in said analyte-containing fluid is a different type of analyte than the analyte to be detected in the external medium.
11. The sensing device of claim 1 , wherein said indicator molecule has an optical characteristic responsive to the presence of oxygen.
12. The sensing device of claim 11 , wherein said indicator molecule is tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) perchlorate.
13. 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.