High-Pressure Fluorescence Flow Cell for Supercritical Fluid Chromatography
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Solution Overview
Problem
Conventional fluorescence detectors for supercritical fluid chromatographs cannot withstand pressures of 10 MPa or higher, limiting their use in high-pressure supercritical fluid chromatography due to the inability of existing optical flow cells to maintain structural integrity under such pressures.
Innovation Solution
A high-pressure fluorescence flow cell made of light-transmissive materials like silica glass or sapphire, with a straight-line flow path and optimized wall thickness to diameter ratio, is designed to withstand pressures of 10 MPa or higher, coupled with a flow cell assembly that includes entry and exit-side cell holders and pressing means to maintain the flow cell under high pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional optical flow cell is used in a fluorescence detector, then the cell volume can be minimized to prevent sample diffusion, but the cell cannot withstand pressures of 10 MPa or higher
Solution Approach 1:
The patent changes the geometric parameters of the flow cell, specifically the wall thickness to diameter ratio (t/d), to achieve the required pressure resistance. By optimizing this ratio, the flow cell can withstand 10 MPa or higher pressures while maintaining a minimized cell volume for efficient fluorescence detection
Solution Approach 2:
The flow cell is constructed using light-transmissive materials such as silica glass or sapphire that possess both optical transparency for fluorescence detection and sufficient mechanical strength to withstand high pressures. This composite approach combines optical and mechanical properties in a single material system
2Measurement precision
If the cell volume is minimized to prevent sample diffusion, then detection sensitivity is improved, but the optical path length decreases reducing fluorescence signal
Solution Approach 1:
The patent directs excitation light parallel to the flow path direction, utilizing the longitudinal dimension of the cell to maximize optical path length. This dimensional approach allows the optical path to extend through the length of the cell rather than being limited by the cross-sectional area, thereby maintaining fluorescence signal intensity despite minimized cell volume
3Use of energy by moving object
If excitation light is directed perpendicular to the flow path, then the optical path length is maximized for a given cell cross section, but the cell volume increases causing sample diffusion
Solution Approach 1:
The patent utilizes the longitudinal dimension of the cell by directing excitation light parallel to the flow path. This allows the optical path length to be determined by the cell length rather than cross-sectional dimensions, achieving sufficient optical path length without increasing cell volume and preventing sample diffusion
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 the use of fluorescence detectors in supercritical fluid chromatography by providing a minimized cell volume with high pressure resistance, enhancing detection sensitivity and allowing for efficient fluorescence detection of high-pressure fluids.
Implementation Method 1
Fluorescence detectors (FLDs) for detecting fluorescence (including phosphorescence) of excited sample constituents
Data Source
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AI summary
A high-pressure fluorescence flow cell comprises a cell body made of a light-transmissive material, wherein the cell body is penetrated by a straight-line flow path for a high-pressure fluid, wherein the flow path is formed with a cross section of 0.1 mm2 to 5 mm2, both inclusive, orthogonal to its longitudinal direction, wherein the ratio t/d of the wall thickness t (mm) to the width d (mm) of the flow path satisfies formula (1) below, td≧12×σ+Pσ-P-1×1.5 where σ indicates the tensile stress (MPa) of the material of the cell body, and P indicates the withstand pressure (MPa) of the cell body.