Combination optical hemoglobin and electrochemical lead assay
A sensor and analyzer for measuring an analyte in a liquid sample are disclosed. The sensor includes a substrate with a reservoir disposed therein. The reservoir may include a top surface and a bottom surface, at least one transparent portion forming at least a part of the bottom surface of the reservoir, and a reflector disposed on the upper surface of the reservoir at a location opposite the at least one transparent portion. The analyzer may include a support surface, an aperture extending through the support surface, a light source disposed below the support surface and oriented so that at least a portion of the light emitted from the light source passes through the aperture, and a detector configured to measure an intensity of light received at the detector.
1. A method for measuring an analyte in a liquid sample, the method comprising:
flowing a liquid sample into a reservoir of a sensor, the reservoir comprising a first portion comprising a first depth and a second portion comprising a second depth that is greater than the first depth, wherein the reservoir is bounded by a first side and a second side such that the liquid sample within the reservoir is positioned between the first side and the second side;
determining a measurement of the analyte in the liquid sample by:
illuminating the liquid sample in the first portion of the reservoir through a transparent portion of the sensor, wherein the transparent portion of the sensor is on the first side of the first portion of the reservoir;
determining a reflectance of the liquid sample based on a measurement of light reflected off a reflector positioned on the second side of the first portion of the reservoir, wherein light for illuminating the sample passes through the transparent portion on the first side of the reservoir, through the liquid sample in the reservoir, and is reflected off the reflector on the second side of the reservoir; and
determining the measurement of the analyte based on the determined reflectance.
2. The method of claim 1 , wherein the reflectance is determined by comparing a measured intensity to a reference intensity.
3. The method of claim 2 , further comprising measuring the reference intensity by:
illuminating an empty sensor; and
measuring a reflectance of the empty sensor.
4. The method of claim 2 , further comprising:
measuring internally reflected stray light by detecting the intensity of light reflected from a light absorbing surface on the sensor;
subtracting the measured internally reflected stray light from the reference intensity and the measured intensity.
5. The method of claim 4 , wherein measuring the internally reflected stray light comprises measuring the internally reflected stray light by detecting the intensity of light reflected from a light absorbing surface on the sensor as the sensor is inserted into or withdrawn from an analyzer.
6. The method of claim 1 , further comprising measuring a second analyte in the liquid sample using an electrode positioned within the reservoir of the sensor.
7. The method of claim 6 , wherein the electrode is positioned within the second depth of the reservoir.