Sample Injection Needle Switching for Carryover Prevention
Solution Overview
Problem
Conventional liquid chromatographs face issues with carryover, which degrades analysis reliability, and existing solutions with two sample injection needles require complex control and can disrupt mobile phase flow, leading to pressure variations and potential leaks.
Innovation Solution
A sample injector system with a first switching valve for connecting the sample injection needle to either the sample suction part or mobile phase supply part, and a second switching valve for continuous mobile phase supply, preventing carryover while maintaining a relatively inexpensive configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two sample injection needles are provided to prevent carryover, then detection accuracy is improved, but device complexity increases and control becomes complicated
Solution Approach 1:
The system segments the injection process into two distinct phases: sample intake phase (needle connected to sample vial) and injection phase (needle connected to injection port). This segmentation allows the same needle to be used for both functions at different times, eliminating the need for a second needle while maintaining carryover prevention through proper path isolation.
Solution Approach 2:
The switching valve dynamically changes the flow path configuration between sample intake and injection modes. By dynamically reconfiguring the connections rather than using fixed dual-needle architecture, the system achieves flexible operation with simpler hardware, reducing device complexity while maintaining detection accuracy.
2Reliability
If two sample injection needles are used with switching control, then carryover is prevented, but productivity decreases due to interruption in mobile phase flow
Solution Approach 1:
The mobile phase flow is maintained continuously throughout the entire operation cycle. During sample intake, the mobile phase flows through the alternative path (port b to column) while the needle is filling with sample. During injection, the mobile phase flows through the needle path (port a to column). This continuous flow eliminates interruptions, maintaining productivity while ensuring carryover prevention through proper path isolation at each phase.
3Reliability
If two sample injection needles are implemented, then carryover is reduced, but ease of operation deteriorates due to special considerations for liquid leakage
Solution Approach 1:
The system extracts the potential leakage problem from the operation by providing a dedicated waste path (port c) for sample disposal. The switching valve isolates the sample path from the mobile phase path during sample intake, and provides a controlled discharge path to waste. This extraction of the leakage risk into a controlled, isolated path eliminates the need for special operator considerations while maintaining reliable carryover prevention.
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
Prevents carryover and improves detection accuracy by ensuring continuous mobile phase supply without interrupting flow, using a simple and cost-effective configuration.
Implementation Method 1
a sample suction part connectable to the sample injection needle and configured to cause a predetermined amount of the sample to be drawn by suction into the sample injection needle
Data Source
AI summary
A sample injection part connected to a column to inject a sample into the column; a sample injection needle attachable to the sample injection part; a sample suction part connectable to the sample injection needle and configured to cause a predetermined amount of the sample to be drawn by suction into the sample injection needle upon connecting to the sample connection needle; a mobile phase supply part configured to supply the column with a mobile phase; a first switching valve for selectively connecting the sample injection needle to one of the sample suction part and the mobile phase supply part; and a second switching valve, including the sample injection part, for supplying the sample and the mobile phase to the column via the sample injection needle in the case of having the sample injection needle attached to the sample injection part and for supplying the mobile phase to the column via the first switching valve in the case of having the sample injection needle removed from the sample injection part are included.