Automatic Sampler Needle Septum Penetration Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional automatic samplers for liquid chromatographs face issues with sample contamination and reduced sample quantity due to air pressure changes when the sampling needle penetrates the septum, and grooved needles are difficult to polish, leading to poor carry-over performance.
Innovation Solution
An automatic sampler with a control unit that operates in specific modes to prevent septum penetration-induced air pressure changes, using a cylindrical sampling needle without grooves, and employing septum penetration, sample suction, and sample injection operations in controlled sequences to ensure precise sample extraction and minimize contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a grooved sampling needle is used to prevent air pressure changes during septum penetration, then air can enter and exit the sample container through the groove, but the groove portion is difficult to polish and has greater surface roughness leading to poor liquid repellency and sample contamination
Solution Approach 1:
The invention extracts the harmful groove feature from the sampling needle design and replaces it with a smooth cylindrical surface. The air pressure control function is achieved not through grooves but through controlled septum penetration operations that allow air to enter and exit through the septum itself, eliminating the need for grooves and their associated contamination problems.
Solution Approach 2:
The invention changes the surface geometry parameter from grooved to smooth cylindrical, which improves polishability and liquid repellency. Simultaneously, it changes the air pressure control mechanism from groove-based to septum-based, achieving the same functional outcome with superior surface properties.
2Quantity of substance
If the sampling needle penetrates the septum to suck sample, then sample can be extracted from the container, but air pressure in the sample container changes causing air to enter the sample suction port and reduce the amount of sample sucked
Solution Approach 1:
The invention performs preliminary air pressure equalization by allowing air to enter and exit the sample container through the septum before sample suction begins. This preliminary action prevents air pressure changes during the subsequent sample extraction, ensuring accurate sample quantity measurement.
Solution Approach 2:
The septum serves as an intermediary mechanism for air pressure control. Instead of relying on groove structures, the septum itself mediates the air pressure balance by allowing controlled air exchange between the sample container and the sampling needle, preventing air from entering the suction port during sample extraction.
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
The solution prevents air pressure changes in the sample container, allows for easy polishing of the sampling needle, and reduces contamination, resulting in improved quantitativeness and stability of peak area values during analysis.
Implementation Method 1
a sampling needle is moved down toward a sample container so as to penetrate a septum hermetically sealing the sample container. Then, a predetermined amount of a sample is sampled from the sample container by sucking the sample through the tip of the sampling needle
Data Source
AI summary
After a sampling needle is moved to a position above a sample container, the sampling needle is moved down so that the tip of the sampling needle penetrates a septum, and is then preferably moved down to a position at which the tip of the sampling needle is not brought into contact with a sample contained in the sample container, and then, the sampling needle is once elevated until the sampling needle is pulled out of the septum, and is then again moved down to penetrate the septum until the tip of the sampling needle is inserted into the sample to suck the sample through a suction port of the sampling needle, and then, the sampling needle is moved to a sample injection port of an analyzer to inject the sample into the analyzer.