Autosampler Injection Valve Switching for Stable Chromatography Pressure
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Solution Overview
Problem
The existing autosampler technologies face challenges in suppressing pressure fluctuations and ensuring reproducibility during the switching of the injection valve from the sample filling state to the sample injection state, leading to pressure shocks that affect the analysis results and column life, particularly in high-pressure supercritical fluid chromatography.
Innovation Solution
The autosampler employs a staged switching mechanism where the injection valve transitions from the sample filling state to an intermediate state and then to the sample injection state, ensuring one end of the sample loop is always connected to the liquid delivery channel and analysis channel before the other, and includes a control mechanism to manage the rotor's drive speed and pressure recovery, thereby stabilizing the flow rate and composition of the mobile phase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the injection valve is switched directly from sample filling state to sample injection state, then the switching operation is simple and fast, but pressure fluctuation occurs in the liquid delivery channel and analysis channel
Solution Approach 1:
The switching process is divided into three distinct states: sample filling state, intermediate state, and sample injection state. The intermediate state acts as a transition phase where one end of the sample loop is connected to the liquid delivery channel while the other end remains closed, allowing gradual pressure equalization and eliminating sudden pressure fluctuations during switching.
Solution Approach 2:
Before completing the full switching to sample injection state, the system first enters an intermediate state where the sample loop is partially connected. This preliminary connection allows the liquid delivery channel to gradually pressurize the sample loop, preventing sudden pressure changes when the final connection is made.
2Reliability
If a channel is provided in the stator for continuous communication between liquid delivery channel and analysis channel, then pressure fluctuation is suppressed, but device complexity and manufacturing cost increase
Solution Approach 1:
Instead of providing continuous communication through a fixed channel in the stator, the patent uses a dynamic switching mechanism where the rotor rotates to establish different connection configurations. The intermediate state is achieved by rotating the rotor to a specific position where the channel connects one end of the sample loop to the liquid delivery channel while closing the other end, providing pressure stability without requiring additional stator channels.
3Ease of operation
If the injection valve switching is performed without control over pressurization sequence, then the operation is simple, but analysis reproducibility deteriorates due to uncertain pressurization direction
Solution Approach 1:
The switching process is segmented into distinct states with controlled transition sequences. The intermediate state ensures that pressurization always occurs from a consistent direction (through the first loop port), eliminating the uncertainty of pressurization direction and improving analysis reproducibility while maintaining operational simplicity through automated control.
Solution Approach 2:
The control unit monitors the rotation position of the rotor and automatically controls the switching sequence to ensure the intermediate state is reached before final injection state. This feedback mechanism ensures consistent pressurization direction without requiring manual intervention, maintaining ease of operation while improving reproducibility.
Data Source
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AI summary
An autosampler sets an injection valve to be in a sample filling state when a sample loop is filled with a sample, and, after completion of filling with the sample, switches the injection valve to an intermediate state and first connects only one end of the sample loop to a liquid delivery channel and an analysis channel. After the above, the injection valve is switched to the sample injection state and the sample loop is interposed between the liquid delivery channel and the analysis channel, so that the sample is injected into the analysis channel.