Optoelectronic methods and devices for detection of analytes
Herein are disclosed optoelectronic methods and devices for detecting the presence of an analyte. Such methods and devices may comprise at least one sensing element that is responsive to the presence of an analyte of interest and that may be interrogated optically by the use of at least one light source and at least one light detector.
1. A method of monitoring an analyte in an atmosphere, comprising:
a) exposing at least one sensing element to an atmosphere potentially containing an analyte for a period of time;
b) directing light in a first wavelength range onto the at least one sensing element and obtaining a first signal that is representative of an amount of light in the first wavelength range reflected from the at least one sensing element;
c) directing light in a second wavelength range onto the at least one sensing element and obtaining a second signal that is representative of the amount of light in the second wavelength range reflected from the at least one sensing element;
d) comparing the first and second signals to provide a compared signal; and,
e) correlating the compared signal to a predetermined response curve and thereby obtaining a concentration value that is associated with the concentration of the analyte in the monitored atmosphere.
2. The method of claim 1 further comprising repeating steps b), c) d) and e) over at least a portion of the period of time of the exposure of the sensing element to the atmosphere potentially containing the analyte.
3. The method of claim 1 wherein the compared signal is a ratioed signal obtained by dividing one of the first and second signals by the other of the first and second signals.
4. The method of claim 1 wherein the sensing element is not exposed to a calibration gas containing a known concentration of analyte, prior to the monitoring of an atmosphere potentially containing the analyte.
5. The method of claim 1 wherein the sensing element comprises a reflection spectrum comprising one or more peaks and valleys of light intensity versus wavelength and wherein the first wavelength range is at or near a peak of the spectrum and the second wavelength range is at or near a valley of the spectrum.
6. The method of claim 1 wherein the method includes the step of obtaining an initial compared signal with the sensing element exposed to an atmosphere free of analyte and determining whether the initial compared signal is in an acceptable range.
7. The method of claim 1 wherein steps b) and c) are sequential steps that are performed with a time delay in between of at least 1 millisecond.
8. The method of claim 1 wherein the light in the first wavelength range is directed from a first narrowband light source and the light in the second wavelength range is directed from a second narrowband light source.
9. The method of claim 8 wherein the first signal that is representative of an amount of light reflected from the at least one sensing element in the first wavelength range, and the second signal that is representative of an amount of light reflected from the at least one sensing element in the second wavelength range, are both obtained from a single broadband light detector that measures light reflected from the sensing element.
10. The method of claim 1 further comprising directing light in a third wavelength range onto the at least one sensing element and obtaining a third signal that is representative of the amount of light in the third wavelength range reflected from the at least one sensing element and comparing the third signal to at least one of the first and second signals.
11. The method of claim 1 further comprising providing a notification signal that is representative of the concentration value.
12. The method of claim 11 wherein the notification signal is recorded in memory.
13. The method of claim 12 wherein the first and second signals and the compared signal are also stored in memory.
14. The method of claim 11 wherein the notification signal is transmitted to a receiving station.
15. The method of claim 1 wherein at least the first signal is obtained from a light detector that is arranged to measure an amount of light reflected by the at least one sensing element.
16. The method of claim 15 wherein the sensing element is a disposable sensing element that comprises an analyte-responsive layer and further comprises an analyte-permeable, semireflective layer between the analyte-responsive layer and the light detector.
17. The method of claim 1 wherein the atmosphere is an air atmosphere.
18. The method of claim 17 wherein the method is performed by a device that is a personal monitor that is worn on the body or clothing of a person.
19. The method of claim 17 wherein the method is performed by a device that performs area monitoring of an indoor or outdoor air atmosphere.