Sample Introduction Needle Carry-Over Reduction
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Solution Overview
Problem
The existing sample introduction methods for liquid chromatographs face issues with carry-over, where residual samples are left behind, affecting the accuracy of subsequent analyses, especially in ultra-micro analysis, due to abrasion of flow path components leading to altered communication statuses and sample retention in gaps between the needle and injection port.
Innovation Solution
A sample introduction method that involves switching the flow path switching valve to reduce sample volume forced into gaps by drawing samples into a sample loop and using a cleaning or intermediate fluid to create a layer between the sample and needle tip, then inserting the needle into the injection port, ensuring the mobile phase solution flushes out residual samples effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the needle is inserted into the injection port to deliver samples, then sample introduction is achieved, but residual samples are forced into gaps between the needle and injection port causing carry-over
Solution Approach 1:
The patent applies preliminary action by switching the flow path valve to connect the needle tip to the sample loop BEFORE inserting the needle into the injection port. This preliminary connection ensures that any sample forced into the gap during insertion is immediately drawn into the sample loop by the mobile phase flow, preventing carry-over to the next sample analysis.
Solution Approach 2:
The patent uses the mobile phase solution as an intermediary fluid that flows through the sample loop to draw residual samples out of the needle tip and injection port gap. The mobile phase acts as a carrier that transports any trapped sample residues to the sample loop, preventing them from contaminating subsequent analyses.
2Extent of automation
If flow path switching valve components are used to switch between injection and cleaning modes, then automated operation is achieved, but abrasion of components alters communication status causing samples to be forced into gaps
Solution Approach 1:
The patent applies preliminary action by switching the flow path valve to connect the needle tip to the sample loop BEFORE inserting the needle into the injection port. This preliminary connection ensures that any sample forced into the gap during insertion is immediately drawn into the sample loop by the mobile phase flow, preventing carry-over to the next sample analysis.
Solution Approach 2:
The patent implements feedback by using the mobile phase flow through the sample loop to continuously monitor and correct for any sample residues. The flow path switching valve responds to the insertion event by maintaining the needle-to-sample-loop connection, allowing the system to self-correct for wear-induced communication changes through the continuous flushing action.
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
This method significantly reduces carry-over, enhancing the precision of sample analysis by minimizing residual samples between the needle and injection port, thereby improving the accuracy of ultra-micro analysis and maintaining analytical device performance.
Implementation Method 1
the mobile phase solution flushes out residual samples effectively
Data Source
AI summary
A sample introduction method for reducing carry-over is provided. After a sample introduction device in a total volume injection method draws a proper amount of a sample solution from a sample container and further draws a solution with the same composition as a mobile phase solution with a needle 24, the needle 24 is inserted into an injection port 25. When flow paths are switched to communicate a liquid feeder, a sample loop 23, the needle 24, the injection port 25, and a separation/detection section, the solution with the same composition as the mobile phase solution is forced into a gap between the injection port 25 and the needle 24. Therefore, the samples squeezed out of a tip section of the needle 24 during the switching of the flow paths are prevented from being forced into the gap between the needle 24 and the injection port 25.