Non-invasive pH Reader Using Light Absorbance Ratio
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Solution Overview
Problem
Current pH measurement methods in cell culture media are invasive, contaminating the sample, lack accuracy and precision, require significant fluid withdrawal, and are not suitable for automated monitoring, especially in sterile environments where immersible devices can foul.
Innovation Solution
A non-invasive pH reader using a ratio of light absorbance at specific wavelengths, employing at least two LEDs and a photodiode to measure pH in solutions containing pH indicators like phenol red, without direct contact, allowing for automated and accurate monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an electrochemical or optical pH probe is placed into the fluid to measure pH, then a digital readout is obtained, but a significant amount of solution must be drawn and the testing process can contaminate the solution
Solution Approach 1:
The patent introduces an intermediary pH indicator dye that chemically reacts with hydrogen ions in the solution to produce a color change. This mediator allows pH measurement without direct contact between the measurement device and the solution, eliminating contamination while maintaining measurement accuracy through optical detection of the color change.
Solution Approach 2:
The patent replaces the mechanical/electrochemical probe system with an optical detection system. Instead of using an electrochemical probe that requires physical insertion into the solution, the invention uses light absorption measurements at specific wavelengths to detect pH, substituting a non-contact optical method for the contact-based mechanical probe approach.
2Ease of manufacture
If color indicator paper is used to measure pH, then the method is inexpensive and requires little wasted sample, but it is neither accurate nor precise and cannot be automated
Solution Approach 1:
The patent replaces the manual visual assessment method with an automated optical detection system. Instead of relying on human eyes to compare color changes against a reference chart, the invention uses a light source and photodetector to objectively measure absorbance at specific wavelengths, enabling automated, precise, and reproducible pH measurements while maintaining cost-effectiveness.
Solution Approach 2:
The patent implements a feedback mechanism where the optical detection system measures light absorbance, converts it to pH values through calibration curves, and provides digital output that can be used for automated monitoring and control. This closed-loop approach enables precise, reproducible measurements that can be integrated into automated systems.
3Measurement precision
If a measured amount of color indicating solution is added to a measured amount of solution sample, then pH can be determined, but a significant amount of fluid must be drawn and then contaminated with the color change solution so that it is no longer useful
Solution Approach 1:
The patent uses a pH indicator dye as an intermediary that can be added in trace amounts to the solution. The dye undergoes a color change in response to pH changes, and this change is detected optically. Because the detection is non-contact and requires minimal dye concentration, the solution remains essentially uncontaminated and can be reused, eliminating the waste problem associated with traditional color indicator methods.
Solution Approach 2:
The patent replaces the method of adding significant volumes of color indicator solution with trace amounts of pH indicator dye detected by optical means. Instead of using bulk color change solutions that contaminate the sample, the invention uses light absorption measurements to detect pH, requiring minimal chemical addition and producing no contamination.
4Measurement precision
If an immersible pH probe is used in cell culture liquids, then pH measurement is possible, but the probe must interact directly with the liquid which can foul the device
Solution Approach 1:
The patent introduces a pH indicator dye as an intermediary that allows indirect pH measurement. Instead of inserting a probe that physically contacts and potentially fouls the cell culture liquid, the invention adds trace amounts of indicator dye and detects pH through optical measurements through the container wall, eliminating direct contact between the measurement device and the sterile liquid.
Solution Approach 2:
The patent replaces the immersible electrochemical probe with a non-contact optical detection system. Instead of mechanically inserting a probe into the sterile cell culture environment, the invention uses light transmission through the container to detect pH, eliminating the risk of contamination and device fouling while maintaining measurement capability.
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 precise, non-invasive, and automated pH measurement in cell culture media, reducing contamination risks and maintaining sterility, with robust and long-lasting electro-optical components, suitable for various container formats and applications.
Implementation Method 1
The pH of a solution is related to the absorbance of light by a pH indicator dye in the solution at different wavelengths
Data Source
AI summary
A method for non-invasively determining a chemical property of an aqueous solution is provided. The method provides the steps of providing a colored solute having a light absorbance spectrum and transmitting light through the colored solute at two different wavelengths. The method further provides the steps of measuring light absorbance of the colored solute at the two different transmitted light wavelengths, and comparing the light absorbance of the colored solute at the two different wavelengths to determine a chemical property of an aqueous solution.