Sample Injection Valve with Bypass Channel for HPLC
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Solution Overview
Problem
Conventional rotary shear seal injection valves in HPLC systems experience destructive pressure and flow transients during sample injection, leading to column degradation and reduced separation efficiency, especially under high-pressure VHPLC conditions.
Innovation Solution
The design incorporates arc-shaped rotor channels and modified stator ports to maintain continuous fluid communication between the pump and column, eliminating flow blockages and using a bypass channel to minimize pressure transients, while also controlling sample loop pressurization and decompression to prevent column damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional rotary shear seal injection valves are used for sample injection in HPLC systems, then sample injection can be performed with simple valve structure, but destructive pressure and flow transients occur during injection causing column degradation
Solution Approach 1:
The injection valve is divided into separate functional modules: a sample injection valve for introducing sample, a bypass valve for alternative flow paths, and a main flow valve for controlling mobile phase flow. This segmentation allows each component to handle specific functions independently, preventing the harmful transients that occur in conventional integrated valves during switching operations.
Solution Approach 2:
A bypass channel is introduced as an intermediary flow path between the pump and column. During sample injection, the bypass valve redirects mobile phase flow through this intermediate channel, preventing direct flow blockage and the associated pressure transients from reaching the column. The bypass acts as a mediator that decouples the injection process from the main flow path.
2Productivity
If sample injection is performed at high pressure VHPLC conditions, then separation efficiency is improved, but column degradation accelerates due to pressure transients
Solution Approach 1:
The bypass channel provides continuous mobile phase flow from the pump to the column during sample injection, eliminating flow interruptions. This continuous flow maintains stable pressure conditions at the column inlet, protecting the column from transient pressure shocks while preserving the high-pressure VHPLC operating conditions necessary for maintaining separation efficiency throughout the injection process.
Solution Approach 2:
The bypass valve and channel are positioned to cushion the impact of pressure transients before they can reach the column. By providing an alternative low-resistance flow path, the bypass system absorbs and dampens pressure fluctuations during valve switching, preventing these transients from damaging the column while allowing the main system to operate at high pressure for optimal separation performance.
3Measurement precision
If flow blockage is used to control sample injection timing, then injection precision is achieved, but pressure transients are generated that harm the column
Solution Approach 1:
The bypass channel serves as an intermediary flow path that allows precise control of sample injection timing without creating harmful flow blockages. The bypass valve can be opened or closed independently to control when sample enters the system, while the main flow path remains open and uninterrupted, preventing the pressure transients that would otherwise be generated by complete flow blockage and release.
Solution Approach 2:
The flow control function is segmented into two independent pathways: the main flow path for mobile phase delivery and the bypass path for sample injection control. This allows precise timing control of sample introduction through the bypass valve while the main valve maintains continuous, stable flow to the column, eliminating the coupled blockage-transient problem of conventional single-pathway valves.
Data Source
AI summary
The present invention provides a method and apparatus for substantially eliminating destructive transients of pressure or flow rate which can degrade the efficiency and useful lifetime of chromatography columns. The present invention enables a substantially constant flow of mobile phase liquid to be maintained through the chromatography system by eliminating the flow blockage interval associated with the actuation of sample injection valves. The present invention further provides a method to reduce the pressure and flow rate transients associated with pressurization of the sample loop contents when the sample loop is introduced to chromatography system delivery pressure.