Time-Resolved Raman Spectroscopy for Chlorinated Solvent Detection
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Solution Overview
Problem
Current methods for determining chlorinated solvent concentrations in aqueous solutions, particularly in situ, face challenges due to high detection limits, interference issues, and limited sensitivity, making it difficult to accurately quantify these contaminants in environmental samples.
Innovation Solution
A method utilizing Time-Resolved Raman Spectroscopy (TRRS) that measures the intensity of Raman return at specific shifts associated with the O—H stretching region of water to develop calibration profiles for determining chlorinated solvent concentrations, even in turbid solutions, by correcting for turbidity and leveraging the influence of chlorine on water vibrational modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional Raman spectroscopy is used for in-situ detection of chlorinated solvents, then the method is simple and can be performed directly at the source, but the detection sensitivity is insufficient and detection limits are too high
Solution Approach 1:
The patent employs time-resolved Raman spectroscopy with pulsed laser excitation, where the laser is pulsed and the Raman signal is collected during specific time windows. This periodic action separates the Raman signal from continuous background fluorescence, significantly improving detection sensitivity for chlorinated solvents in aqueous environments while maintaining a relatively simple probe-based measurement system
Solution Approach 2:
The patent changes the temporal parameter of the measurement system by introducing time resolution to the Raman spectroscopy. By measuring the Raman signal at different time delays after laser excitation, the system exploits the different decay times of Raman scattering versus fluorescence to enhance sensitivity and selectively detect chlorinated solvent signals against background interference
2Measurement precision
If direct Raman spectroscopy is used to measure chlorinated solvent concentrations, then the measurement process is straightforward, but interference from water and other matrix components reduces accuracy
Solution Approach 1:
The patent extracts the useful Raman signal from the complex spectral background by using time-resolved measurement. The system separates the short-lived Raman scattering signal from the longer-lived fluorescence background through temporal gating, effectively extracting the chlorinated solvent signal from interfering water and matrix components
Solution Approach 2:
The patent introduces time delay as an intermediary parameter to separate the desired Raman signal from interfering signals. By measuring at different time windows after laser excitation, the system uses temporal separation as a mediator to distinguish chlorinated solvent Raman peaks from water and background fluorescence, improving measurement accuracy
3Productivity
If traditional detection methods are used for chlorinated solvents in groundwater, then the equipment is well-established and reliable, but the methods require sample collection and laboratory analysis which reduces productivity and increases cost
Solution Approach 1:
The patent implements an in-situ measurement system that performs detection directly in the groundwater environment without requiring sample collection, transport, or laboratory processing. The probe-based Raman system measures chlorinated solvent concentrations in place, eliminating the need for external laboratory analysis and significantly improving monitoring productivity while achieving detection limits suitable for environmental regulation
Solution Approach 2:
The patent replaces the mechanical/chemical sample handling system with an optical measurement system. Instead of collecting physical samples and analyzing them in the laboratory, the system uses light-based Raman spectroscopy to detect chlorinated solvents in situ, substituting mechanical sample processing with optical field measurement to improve efficiency
4Adaptability or versatility
If Raman spectroscopy is used in turbid aqueous solutions, then the method can handle complex environmental matrices, but turbidity causes scattering and absorption that reduces signal intensity and measurement accuracy
Solution Approach 1:
The patent uses time-resolved measurement with pulsed excitation to separate the Raman signal from turbidity-induced scattering. By collecting signals during specific time windows when Raman scattering occurs but later scattering has decayed, the system maintains measurement accuracy in turbid environmental samples while preserving signal intensity
Data Source
AI summary
Method for determining concentration of a chlorinated solvent in a non-turbid aqueous solution sample containing the chlorinated solvent is disclosed. The method includes developing a calibration profile relating intensities of Raman returns at a predetermined Raman shift associated with O—H stretching region of water for non-turbid aqueous chlorinated solvent calibration solutions of known concentrations. Intensity of Raman return at the predetermined Raman shift associated with O—H stretching region of the non-turbid aqueous solution sample is measured and compared to the calibration profile to determine the concentration of the chlorinated solvent in the non-turbid aqueous solution sample. For turbid solution samples, a method using turbidity-corrected intensity for the solution sample is disclosed. Alternatively, for turbid solution samples, a method employing a calibration profile utilizing turbid calibration solutions is disclosed.