Multi-Path Flow Cell for Wide-Range Optical Density Measurement
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Solution Overview
Problem
Existing spectrophotometry systems face challenges in determining optical density of solutions with wide dynamic ranges without the need for dilution, particularly in chromatography or filtration systems, due to issues with mechanical adjustments and slow response times in variable path length systems, and difficulties in maintaining linear dynamic ranges in fixed multi-light path systems.
Innovation Solution
A flow cell with multiple fixed light paths of predetermined lengths is used to determine optical density by calculating and comparing slopes of absorbance readings, selecting the appropriate slope based on path length differences, ensuring all paths are within the linear dynamic range or using the steepest slope when they are not.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a variable path length system is used to extend the linear dynamic range, then the measurement range is improved, but the response time deteriorates due to mechanical adjustment delays
Solution Approach 1:
The flow cell is divided into multiple fixed light paths with different path lengths (e.g., 1mm, 2mm, 5mm, 10mm) arranged in parallel. Each path length is optimized for specific absorbance ranges, allowing the system to handle a wide dynamic range without mechanical adjustments. The segmentation enables simultaneous measurement at multiple path lengths, eliminating the time delay associated with sequential mechanical adjustments.
Solution Approach 2:
The system dynamically selects which light path to use based on the sample's absorbance characteristics. By comparing absorbance readings from multiple fixed paths, the system automatically determines the appropriate path length for accurate measurement, providing adaptive response without mechanical movement.
2Measurement precision
If dilution is performed to bring absorbance within the linear range, then measurement accuracy is improved, but the measurement process complexity increases
Solution Approach 1:
Instead of requiring sample dilution, the system segments the measurement into multiple fixed path lengths. Each path length is designed to accommodate specific concentration ranges, allowing direct measurement of undiluted samples across a wide dynamic range while maintaining accuracy within the linear range for each path.
3Speed
If a fixed multi-light path system is used to avoid mechanical adjustments, then the response time is improved, but the path length precision requirements increase
Solution Approach 1:
The system measures absorbance at multiple fixed path lengths simultaneously and uses feedback algorithms to identify the most appropriate path length for the current sample. By comparing readings from all paths and selecting the one that yields an absorbance value within the optimal linear range (e.g., 0.1-1.0 AU), the system compensates for variations in path length manufacturing tolerances.
Solution Approach 2:
The system changes the effective measurement parameter (path length) by selecting among multiple fixed options rather than relying on a single precision-critical dimension. This approach transforms a precision-critical manufacturing requirement into a selection problem that can be resolved through computational analysis of multi-path readings.
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 method provides a fast and accurate determination of optical density without mechanical delays, allowing for high-frequency measurements and improved response times, while maintaining accuracy across varying concentrations.
Implementation Method 1
For a sample substance, e.g. proteins, DNA or RNA, consisting of a single homogeneous substance with a concentration c, the light transmitted through the sample will follow a relationship known as Beer's Law: A=εcl, where A is the absorbance, ε is the absorptivity or extinction coefficient
Implementation Method 2
The at least three light paths are irradiated and electromagnetic radiation going through the at least three light paths detected and absorbance readings, A, of the solution at the at least three light paths taken
Data Source
AI summary
A method and instrument for determining optical density of a solution is disclosed. A flow cell 1 having at least three light paths (4a, 4b, 4c) is provided (100), wherein each light path has a respective predetermined path length, l. Absorbance readings are taken (400), A, of the solution at the at least three light paths (4a, 4b, 4c). For each pair of light paths, a slope, αc, is calculated (500) by dividing a difference in absorbance reading, ΔA, with a difference in path length, Δl. The calculated slopes, αc, are compared (600), and a) if the calculated slopes, αc, are the same, the slope is used for determining (700) optical density of the solution, or b) if the calculated slopes, αc, are not the same, the steepest slope of the calculated slopes is used for determining (701a) optical density of the solution, or the slope of the calculated slopes being in the range of an absorbance reading of 0.01 to 2 is used for determining (701b) optical density of the solution.