Liquid Chromatograph Sample Introduction Without Downstream Valves
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Solution Overview
Problem
The autosampler of direct injection type in liquid chromatographs requires multiple valves, leading to increased dead volume, which deteriorates analysis accuracy by diffusing samples and causing carry-over due to the dead space between pipes and valves.
Innovation Solution
A sample introducing apparatus that eliminates the flow path switching means at the downstream side of the needle, reducing dead volume and preventing sample carry-over by directly connecting the analytical flow path to the separation column without intermediate valves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple valves are used for flow path switching in the autosampler, then the sample injection function is achieved, but the dead volume increases causing sample diffusion and carry-over
Solution Approach 1:
The invention extracts and eliminates the flow path switching means (valves) from the downstream side of the needle. By removing these valves, the dead volume in the analytical flow path is reduced, preventing sample diffusion and carry-over while maintaining the essential sample injection function through alternative flow path configuration.
Solution Approach 2:
The invention segments the flow path into distinct functional zones: the sample introduction flow path (including needle and sample loop) and the analytical flow path (from pump to separation column). By clearly separating these zones and eliminating intermediate valves at the downstream side, the system achieves both functional reliability and measurement precision.
2Ease of operation
If flow path switching means is placed between the needle and separation column, then flow path control is achieved, but dead space causes sample retention and carry-over
Solution Approach 1:
The invention removes the flow path switching means from the critical zone between the needle and separation column. Flow path control is achieved instead by strategic placement of valves only at the upstream side and through the natural configuration of the analytical flow path, eliminating the dead space that causes sample retention and carry-over.
3Adaptability or versatility
If valves are placed in both upstream and downstream flow paths, then complete flow path switching capability is achieved, but the complexity of the system increases
Solution Approach 1:
The invention extracts and removes the downstream valves from the system configuration. Complete flow path switching capability is maintained by strategically placing valves only at the upstream side of the needle and configuring the analytical flow path to provide necessary control without requiring downstream switching components, thereby reducing system complexity.
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 design enhances analysis accuracy by reducing sample diffusion and carry-over, maintaining higher theoretical plate numbers and minimizing sample retention, thus improving the overall precision of liquid chromatography.
Implementation Method 1
The sample introduction flow path, which is connected to a syringe to suck up and discharge a sample in the autosampler, sucks up a sample through the needle as the plunger of the syringe is pulled out.
Data Source
AI summary
Disclosed herein is a sample introducing apparatus which is designed such that the analytical flow path runs from the needle to the separation column without the flow path switching means placed at the downstream side of the needle. This design reduces dead volume, which in turn reduces the diffusion of the sample injected into the analytical flow path. Moreover, the absence of the flow path switching means at the downstream side of the needle to inject a sample into the analytical flow path eliminates connection of the pipe with the flow path switching means. This prevents the sample from remaining in the connecting part, thereby reducing sample carry-over and improving the accuracy of analysis.