Autosampler Injection Valve Switching for Stable Chromatography Pressure
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Solution Overview
Problem
The existing autosampler technologies face issues with pressure fluctuations and 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 the life of the analysis column.
Innovation Solution
The autosampler introduces an intermediate state in the injection valve operation, where one end of the sample loop is connected to the liquid delivery channel and analysis channel before switching to the sample injection state, maintaining communication between the pump and column ports to stabilize pressure and reduce pressure shocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the injection valve is switched directly from the sample filling state to the sample injection state, then the switching operation is simple and fast, but the communication between the liquid delivery channel and the analysis channel is temporarily interrupted causing pressure fluctuation
Solution Approach 1:
The switching operation is divided into three distinct states: sample filling state, intermediate state, and sample injection state. The intermediate state segments the direct transition into two steps, where first one end of the sample loop is connected to the liquid delivery channel, then the other end is connected to the analysis channel. This segmentation prevents complete communication interruption while maintaining manageable switching complexity.
Solution Approach 2:
The intermediate state acts as a mediator between the sample filling state and the sample injection state. During this intermediate state, one end of the sample loop is connected to the liquid delivery channel while the other end remains disconnected from the analysis channel, serving as a transitional buffer that maintains continuous communication path and stabilizes pressure during the switching process.
2Reliability
If a channel is provided in the stator for communicating between the liquid delivery channel and the analysis channel during switching, then pressure fluctuation is suppressed, but the device complexity and manufacturing cost increase
Solution Approach 1:
Instead of providing a permanent communication channel in the stator, the patent uses the dynamic rotation of the rotor to create temporary communication paths. The rotor's rotational position dynamically controls which connection ports are connected, allowing the system to maintain communication during switching without adding permanent structural complexity to the stator.
Solution Approach 2:
The rotor serves multiple functions: it controls the switching between different connection states, maintains communication during transition, and enables the intermediate state. By making the rotor multi-functional, the patent avoids the need for additional dedicated communication channels in the stator, reducing overall device complexity.
3Productivity
If both ends of the sample loop are connected to the liquid delivery channel and analysis channel simultaneously, then the switching is efficient, but errors in processing and assembly cause uncertain pressurization direction affecting reproducibility
Solution Approach 1:
The connection process is segmented into two sequential steps rather than a single simultaneous connection. First, one end of the sample loop is connected to the liquid delivery channel in the intermediate state. Then, in the sample injection state, the other end is connected to the analysis channel. This segmentation eliminates the uncertainty of pressurization direction caused by simultaneous connection errors.
Solution Approach 2:
The connection of one end of the sample loop to the liquid delivery channel is performed as a preliminary action in the intermediate state before the final connection to the analysis channel. This preliminary connection ensures proper pressurization direction is established before complete switching, compensating for potential assembly errors and improving reproducibility.
Data Source
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.