Variable Path Length Spectroscopy for Undiluted Sample Measurement
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Solution Overview
Problem
Existing ultraviolet (UV)/visible spectrophotometers face challenges in accurately determining the concentration of highly concentrated biological samples like proteins, DNA, or RNA without dilution, as they often operate outside the linear range, requiring multiple dilutions that introduce errors and are cumbersome due to large, space-consuming instrumentation.
Innovation Solution
A variable path length spectroscopy system using a compact light source and a movable probe to dynamically change the path length during measurements, allowing concentration determination without needing to know the exact path length, and optionally employing a 'no-reference signal' mode to skip measuring incident intensity variations when stable, thus enhancing flexibility and speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard cuvettes with fixed path length are used in conventional spectrophotometers, then the instrument structure is simple, but the measurement precision deteriorates for highly concentrated samples because they fall outside the linear range requiring dilution
Solution Approach 1:
The patent employs a movable probe that dynamically adjusts the optical path length through the sample. The probe can be positioned at multiple locations along the sample chamber, allowing the path length to be varied during measurement. This dynamic adjustment enables the system to measure highly concentrated samples directly without dilution, resolving the contradiction between measurement precision and device complexity by making the path length adjustable rather than fixed.
Solution Approach 2:
The patent changes the parameter of optical path length to resolve the measurement range issue. By allowing the path length to vary (through probe repositioning), the system can accommodate a wider range of concentrations. The measurement equation A = εCL remains valid, but with L becoming a variable parameter that can be optimized for each sample concentration, eliminating the need for dilution and improving measurement precision while maintaining reasonable instrument complexity.
2Measurement precision
If multiple dilutions of the sample are performed to bring absorbance within the linear range, then the measurement precision improves, but the loss of time increases due to the cumbersome dilution process
Solution Approach 1:
The movable probe enables dynamic adjustment of the optical path length during the measurement process itself, eliminating the need for preliminary dilution steps. The system can directly measure highly concentrated samples by increasing the path length, thereby reducing measurement time while maintaining precision without the time-consuming dilution procedure.
Solution Approach 2:
Instead of performing dilution as a preliminary action before measurement, the patent performs path length adjustment as the measurement action itself. The probe is positioned to define the appropriate path length directly during the absorbance measurement, eliminating the need for separate dilution steps and reducing overall measurement time.
3Measurement precision
If the path length is increased to measure highly concentrated samples, then the measurement precision improves, but the device complexity increases due to the need for variable path length mechanisms
Solution Approach 1:
The patent uses a simple movable probe mechanism rather than a complex variable path length system. The probe can be manually or automatically repositioned to different locations along the sample chamber, providing variable path length with minimal mechanical complexity. This approach achieves the desired measurement precision for concentrated samples without requiring elaborate path length adjustment mechanisms.
4Adaptability or versatility
If a UV/visible spectrophotometer system is used as light source, then the measurement capability is comprehensive, but the volume occupied increases occupying several cubic feet of space
Solution Approach 1:
The patent extracts the essential measurement function from the bulky conventional spectrophotometer system. By using a simplified light source and detector arrangement with a movable probe, the system maintains the core absorbance measurement capability while dramatically reducing the volume required. The essential components (light source, sample chamber with movable probe, detector) are arranged in a compact configuration that occupies minimal space compared to traditional UV/visible spectrophotometers.
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
Enables accurate, rapid, and dynamic concentration measurements of fluid samples without dilution, reducing installation space and measurement time, while maintaining high precision.
Implementation Method 1
Absorption spectroscopy is used to measure composition and/or properties of a material in any phase, gas, liquid, solid. For example, the optical absorption spectra of liquid substances may be measured to determine concentration or other properties of a species of interest, within a liquid medium.
Implementation Method 2
For a sample Consisting of a single homogeneous substance having a concentration c, the light transmitted through the sample will follow a relationship know as Beer's Law: A=εCL where A is the absorbance (also known as the optical density (OD) of the sample at wavelength λ
Data Source
AI summary
A method includes determining whether a variation in probe radiation intensity meets a stability criterion; directing the probe radiation through a probe, when the probe is disposed at a first position, defining a first path length L1 of the probe radiation through the fluid sample; measuring a transmitted intensity I1 of the probe radiation after passing through the fluid sample when the probe is disposed at the first position; directing the probe radiation through the probe when the probe is disposed at a second position, defining a second path length L2 of the probe radiation through the fluid sample; measuring a transmitted intensity I2 of the probe radiation after passing through the fluid sample when the probe is disposed at the second position; and determining a concentration C of a material in the fluid sample based upon L1, I1, L2, and I2, when the stability criterion is met.