Capillary Electrophoresis Injection Valve Design
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Solution Overview
Problem
Traditional capillary electrophoresis instruments face challenges with inaccurate and unreliable sample injection due to high voltage interruptions, cross-contamination, and difficulty in achieving precise nano-liter level injections, leading to poor precision and repeatability.
Innovation Solution
A fully automated high-precision capillary electrophoresis instrument featuring an automatic sampling flow path with a syringe pump, six-channel liquid dispenser, and a four-way sample injection valve with a built-in quantitative loop, which enables rapid, accurate, and precise sample injection while preventing external air entry and allowing for self-cleaning and reagent balancing of the capillary separation columns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional electrophoretic injection or hydrodynamic injection is used, then sample injection can be performed, but cross contamination between sample and buffer solution or between different samples occurs
Solution Approach 1:
The injection system is segmented into separate flow paths for sample and buffer solution, with dedicated injection needles and waste bottles. The four-way valve creates distinct routing segments that prevent mixing between sample, buffer, and waste streams, eliminating cross-contamination while maintaining injection functionality
Solution Approach 2:
A four-way valve is introduced as an intermediary component to control fluid routing between sample injection needle, buffer solution, and waste bottle. This intermediary device enables selective connection of different components, allowing clean separation of sample and buffer paths while maintaining controlled injection flow
2Ease of operation
If high voltage is turned off during injection, then injection can be performed, but the established electric field is interrupted resulting in poor precision of the analysis
Solution Approach 1:
The high voltage electric field is maintained continuously throughout the injection and analysis process. The injection system is designed to operate under applied voltage conditions, with the four-way valve and flow path configuration enabling sample introduction without interrupting the electric field, thus maintaining both injection capability and analysis precision
Solution Approach 2:
Instead of turning off high voltage to perform injection (conventional approach), the system inverts the approach by performing injection while high voltage remains on. The four-way valve enables reverse routing of fluid paths under voltage conditions, allowing injection to occur without field interruption and actually improving precision through continuous field application
3Device complexity
If dip in approach is used for injection, then simple injection is achieved, but repeatability is very poor making it very difficult to achieve quota-sampling
Solution Approach 1:
The manual dip-in mechanical injection method is replaced with an automated four-way valve controlled fluid routing system. This mechanical-to-valve substitution enables precise control of sample flow paths, consistent injection volumes, and repeatable sampling while maintaining operational simplicity through automated valve sequencing
Solution Approach 2:
The injection system changes the control parameter from manual needle positioning (dip-in) to automated four-way valve positioning with defined flow paths. This parameter change from mechanical positioning to valve-controlled flow routing enables precise, repeatable injection volumes and consistent sampling while maintaining ease of operation through automation
4Productivity
If traditional injection methods are used, then injection can be performed, but injection size accuracy at nano-liter level cannot be achieved
Solution Approach 1:
The four-way valve is pre-configured with defined flow paths and connection points for sample and buffer. The injection system performs preliminary routing setup through the valve before actual sample introduction, ensuring that nano-liter level precision is achieved from the start of injection without requiring manual adjustment or calibration during the process
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 significantly improves injection speed, accuracy, and precision, eliminates cross-contamination and electrical bias, and achieves reliable quota-sampling, making the instrument suitable for wide-ranging capillary electrophoresis analysis.
Implementation Method 1
A high-voltage is applied across a capillary filled with the electrolyte during the analysis so that charged molecules within the electrolyte move with different speed and in different direction depending on their electrophoretic mobility
Implementation Method 2
because the electroosmotic flow is always stronger than their electrophoretic mobility, all the compounds in the capillary are eventually carried to the detection end of the capillary
Implementation Method 3
a four-way sample injection valve whose four ports are respectively connected with a sampling needle, a buffer syringe pump, an electrophoretic separation capillary and a shunt waste bottle
Data Source
AI summary
A fully automated high-precision capillary electrophoresis instrument, comprising an electrophoresis system, a sample injection flow path, and an automatic sampling flow path; the sampling flow path comprising a shunt waste bottle, which is connected to a four-way connector, a four-way sample injection valve and a buffer syringe pump; the automatic sampling flow path comprises a sampling needle, a sample tray, a cleaning tank, reagent bottles, a buffer tube, a six-channel liquid dispenser, and a syringe pump. The described capillary electrophoresis instrument has a fast sample injection speed, high accuracy, good reproducibility, and can be widely used in automated analysis of different substances by capillary electrophoresis.