Dual Fluorometer-Absorbance Sensor for Water Quality
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Solution Overview
Problem
Existing optical-based water quality sensors face limitations due to optical interferences, such as fluorescence interference and the inner filter effect, which cause measurement ambiguity and reduce the effective range of fluorescence-based sensors, and absorbance-based sensors struggle with interference from competing species.
Innovation Solution
A dual-function sensor that combines fluorescence and absorbance-based sensing, using multiple LEDs and optical receivers with bandpass filters to simultaneously detect and correct for interferences, allowing for real-time IFE correction and enhanced interference rejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fluorescence-based sensing is used to detect water quality parameters, then the sensor can detect specific fluorophores, but optical interferences from competing fluorescence species cause measurement ambiguity
Solution Approach 1:
The sensor divides the optical detection into two separate paths: a fluorescence detection path with perpendicular geometry and an absorbance detection path with transmission geometry. This segmentation allows each path to specialize in detecting specific aspects of the sample, with the absorbance path specifically designed to measure and correct for interference from competing species.
Solution Approach 2:
The absorbance detection serves as an intermediary measurement that indirectly characterizes the interference from competing fluorescence species. By measuring absorbance at the excitation wavelength, the system obtains information about the concentration of interfering species, which is then used to correct the fluorescence measurements.
2Measurement precision
If fluorescence-based sensing is used, then specific water parameters can be detected, but the inner filter effect significantly limits the effective range
Solution Approach 1:
The absorbance measurement at the excitation wavelength acts as an intermediary that quantifies the inner filter effect. By measuring how much light is absorbed by the sample, the system can calculate the extent of IFE and apply a correction factor to the fluorescence signal, thereby extending the measurable concentration range.
Solution Approach 2:
The system uses absorbance measurement as a feedback signal to continuously monitor and correct for inner filter effect. The absorbance value feeds into the correction algorithm that adjusts the fluorescence reading in real-time, allowing the system to maintain accuracy across a wider range of concentrations.
3Measurement precision
If absorbance-based sensing is used to measure transmitted intensity, then the presence of absorbing species can be determined, but optical interferences from competing species cause measurement ambiguity
Solution Approach 1:
The sensor separates absorbance measurement into a dedicated transmission path with its own optics and detectors. This segmentation allows the absorbance measurement to be optimized for measuring total absorbing species, while the fluorescence path measures fluorophore-specific emission. The two measurements work together to resolve ambiguities.
Solution Approach 2:
The dual-function sensor design allows the same device to perform both absorbance and fluorescence measurements, with each mode serving a specific analytical purpose. The absorbance measurement provides information about total absorbing species, while fluorescence provides species-specific information, together offering comprehensive water quality analysis.
4Measurement precision
If a single sensing body performs both absorbance and fluorescence sensing, then hardware-based IFE correction and interference correction can be realized, but the device complexity increases
Solution Approach 1:
The optical system is segmented into distinct functional modules: excitation light source, fluorescence detection path with perpendicular geometry, absorbance detection path with transmission geometry, and separate detectors for each path. This modular segmentation makes the complex system more manageable and allows each module to be optimized independently.
Solution Approach 2:
The sensor merges absorbance and fluorescence detection capabilities into a single integrated device that shares common components such as the excitation light source and sample chamber. This merging reduces overall system complexity compared to having separate instruments, while still providing the correction capabilities of dual-functionality.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables accurate, real-time correction of interferences, extending the useful range of fluorescence detection and improving the accuracy of absorbance measurements, addressing limitations in existing technologies by allowing simultaneous detection and correction of multiple species.
Implementation Method 1
fluorescence-based sensing, where an excitation light source (at some specified optical wavelength) is used to optically excite the water parameter of interest and re-emit optical light (at a longer optical wavelength) specific to the water parameter of interest
Implementation Method 2
absorbance-based sensing, where the transmitted intensity of optical light is measured by optical sensor across an optical gap to determine the presence of the water quality parameter of interest that absorbs the optical light
Implementation Method 3
employing one or multiple optical bandpass filters, spectrally centered at the specified excitation wavelengths
Data Source
AI summary
A dual function fluorometer-absorbance sensor features an absorbance-based sensor configured to receive one part of an optical signal transmitted through a body of water of interest along an optical beam transmission path, and determine absorbance-based sensor signaling containing information about an absorbance of the optical signal by one or more absorbance species of interest present in the body of water; and a fluorescence-based sensor configured to receive another part of the optical signal transmitted through the body of water of interest along a corresponding optical beam transmission path that is perpendicular to the optical beam transmission path, and determine fluorescence-based sensor signaling containing information about a fluorescence transmitted by one or more fluorophore species of interest present in the body of water.