LC Injector Pressure Control for Precise High-Pressure Sample Injection
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Solution Overview
Problem
Conventional injectors in liquid chromatography systems are limited in their functionality, particularly in terms of flexibility and precision in injecting fluidic samples under high pressure conditions, which affects the reproducibility and efficiency of the sample separation process.
Innovation Solution
The development of an injector system that includes a sample accommodation volume, a sample drive, a fluidic valve switchable between multiple states, and a control unit for pressure adjustment, allowing for precise control of fluid flow and pressure during sample injection, enabling flexible operation and precise sample injection procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional injector is used in liquid chromatography, then the system structure is simple, but the functionality is limited and precision in injecting fluidic samples under high pressure conditions is poor
Solution Approach 1:
The injector is divided into functionally independent modules: a sample introduction unit with sample loop and injection needle, a valve unit with rotor and stator for fluid path switching, and a high-pressure drive unit. This segmentation allows each module to be optimized for its specific function while maintaining overall system flexibility and precision under high pressure conditions.
2Productivity
If high pressure values up to 1200 bar are used in the separation unit, then the separation efficiency is improved, but it becomes necessary to press the rotor against the stator to withstand the pressure in a fluid tight manner
Solution Approach 1:
The rotor is pre-loaded against the stator with a spring mechanism or adjustment mechanism that establishes the necessary contact pressure before high-pressure fluid flow begins. This preliminary action ensures that the rotor-stator interface is already sealed and ready to withstand the full 1200 bar pressure without leakage, while allowing the valve to remain relatively simple in structure.
3Manufacturing precision
If a predefined amount of fluidic sample is intaken into a sample loop by piston movement, then the injection volume is controlled, but the pressure is significantly smaller than what the separation unit operates with
Solution Approach 1:
The valve unit acts as an intermediary between the low-pressure sample introduction system and the high-pressure separation unit. The valve receives the precisely measured sample in the loop at low pressure, then switches fluid paths to introduce this pre-measured sample into the high-pressure flow path, thereby decoupling the volume measurement function from the high-pressure environment and maintaining both precision and pressure compatibility.
4Ease of operation
If an injector valve is switched to introduce the intaken sample from the sample loop into the separation path, then the sample injection is achieved, but the functionality remains limited compared to modern requirements
Solution Approach 1:
The valve unit is designed with multiple fluid paths and switching positions that enable it to perform multiple functions: introducing sample from the loop into the separation path, flushing the loop with mobile phase, bypassing the loop entirely for direct mobile phase flow, and potentially introducing samples from multiple sources. This multi-functionality greatly enhances operational flexibility while maintaining ease of use through a single valve switching mechanism.
Data Source
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AI summary
Injector (40) for injecting a fluidic sample into a flow path (104) between a fluid drive (20) and a separation unit (30) of a sample separation apparatus (10), wherein the injector (40) comprises a sample accommodation volume (100) for accommodating the fluidic sample prior to injecting, a sample drive (102) configured for intaking the fluidic sample into the sample accommodation volume (100), a fluidic valve (95) switchable between multiple switching states to thereby selectively couple the sample accommodation volume (100) with the flow path (104) or decouple the sample accommodation volume (100) from the flow path (104), wherein in an injection switching state of the fluidic valve (95), the fluid drive (20), the separation unit (30) and the sample drive (102) are fluidically coupled by the fluidic valve (95) so that fluid driven by the sample drive (102) and flowing from the sample accommodation volume (100) to the separation unit (30) and further fluid driven by the fluid drive (20) and flowing from the fluid drive (20) to the separation unit (30) are combined at a fluidic connection (108) upstream of the separation unit (30), and a control unit (70) configured for controlling a pressure of at least one of the group consisting of the fluid driven by the sample drive (102), the further fluid driven by the fluid drive (20), and the combined fluid) during injecting fluidic sample from the sample accommodation volume (100) into the flow path (104).