Far-UV Liquid Chromatography Detector with Fixed Reference Photodetector
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Solution Overview
Problem
Conventional liquid chromatography devices face challenges in detecting compounds without absorption in the ultraviolet wavelength band, such as sugars and alcohols, due to strong absorption by solvents and oxygen, leading to low detection sensitivity and increased noise in the far-ultraviolet region.
Innovation Solution
A far-ultraviolet absorbance detection device with a fixedly disposed second photodetector on the −1 order light side of the diffraction grating, utilizing a sealed optical system evacuated with nitrogen gas, and a computation unit for base line correction, which increases the amount of detection light and reduces noise by eliminating the need for a drive device for the reference light photodetector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional UV detector is used, then compounds with UV absorption can be detected, but compounds without UV absorption (such as sugars and alcohols) cannot be detected
Solution Approach 1:
The patent changes the wavelength parameter from conventional UV (200-380 nm) to far-UV (100-200 nm) region, enabling detection of compounds like sugars and alcohols that lack UV absorption but exhibit absorption in the far-UV region
2Ease of manufacture
If far-ultraviolet spectroscopy is performed in air, then absorption spectrum measurement can be conducted, but strong absorption by oxygen makes the device complex and expensive requiring evacuation
Solution Approach 1:
The patent introduces nitrogen gas as an inert atmosphere to replace air in the optical path, eliminating oxygen absorption interference while avoiding the complexity of vacuum evacuation systems
Solution Approach 2:
Nitrogen gas serves as an intermediary substance between the light source and detector, preventing harmful oxygen absorption without requiring mechanical evacuation of the system
3Loss of energy
If the optical path length is shortened to 0.5 mm for far-UV measurement, then transmission through solvent becomes possible, but detection sensitivity decreases
Solution Approach 1:
The patent changes the wavelength parameter to far-UV region where compounds exhibit stronger absorption, allowing use of longer optical path lengths (10 mm) while maintaining high transmission and sensitivity
4Measurement precision
If a movable reference light photodetector is used, then absorbance detection can be performed, but the drive device increases device complexity and reduces evacuation efficiency
Solution Approach 1:
Instead of moving the reference photodetector, the patent fixes the reference photodetector and moves the diffraction grating to direct different wavelengths to the detection path, inverting the conventional approach
5Measurement precision
If a beam splitter is used to create reference and detection light paths, then absorbance measurement can be performed, but the amount of detection light decreases
Solution Approach 1:
The patent segments the optical path into two separate paths: one for reference light detection and another for sample absorption detection, allowing full-intensity light to reach each detector without beam splitter losses
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
This configuration allows for high-sensitivity absorbance measurement in the far-ultraviolet region, enabling detection of compounds with minimal light loss and reduced noise, while simplifying the device and increasing evacuation efficiency.
Implementation Method 1
a diffraction grating that disperses the light emitted from the light source
Implementation Method 2
a first photodetector that detects the light transmitted by the flow cell, and a second photodetector that detects light other than the +1 order light diffracted by the diffraction grating
Implementation Method 3
it is necessary to evacuate the inside of the spectroscopic device because of strong absorption by oxygen in the air
Data Source
AI summary
In order to achieve high sensitivity without an increase in device complexity or cost, a far-ultraviolet absorbance detection device for liquid chromatography is provided with: an optical system including a light source that emits light including far-ultraviolet light, a diffraction grating for dispersing the light emitted from the light source, a flow cell through which a liquid is passed, a slit for selecting a predetermined wavelength of +1 order light diffracted by the diffraction grating and causing the light to enter the flow cell, a first photodetector for detecting the light transmitted by the flow cell, and a second photodetector for detecting light other than the +1 order light diffracted by the diffraction grating; a mechanism for evacuating or substituting the optical system with nitrogen gas; and a computation unit that calculates absorbance from an output signal from the first photodetector and an output signal from the second photodetector. The second photodetector is fixedly disposed.