Mobile Phase Flow Control for LC Back-Flow Prevention
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Solution Overview
Problem
In high-pressure gradient liquid chromatography systems, back-flow of mobile phases during initial stabilization states leads to poor gradient rise and inaccurate analysis, especially in micro and nano LC where flow rates are low, causing issues with airtightness and initial liquid distribution.
Innovation Solution
Incorporating actual flow rate measuring sections downstream of each liquid-feeding pump to detect back-flow and control the driving of pumps to cancel it, ensuring set flow rates are maintained, thereby preventing back-flow and improving gradient rise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a liquid-feeding pump remains in a drive-stopped state to maintain a specific mobile phase composition before analysis, then the initial liquid distribution is simplified, but back-flow occurs causing poor gradient rise and inaccurate analysis
Solution Approach 1:
The system performs preliminary action by detecting back-flow before the actual analysis begins and compensating for it in advance. The control device detects back-flow in the stopped pump's liquid-feeding flow path and calculates compensation values, then applies these compensations when the pump starts feeding, ensuring accurate gradient rise from the beginning of analysis.
Solution Approach 2:
The system implements feedback control by continuously monitoring the liquid-feeding amounts of both pumps and comparing them against expected values. When back-flow is detected in a stopped pump, the system uses this feedback information to calculate and apply compensation values, adjusting the pump operations to maintain accurate mobile phase composition control.
2Manufacturing precision
If back-flow compensation is implemented for one liquid-feeding flow path, then gradient rise accuracy is improved, but system complexity increases due to additional control requirements
Solution Approach 1:
The control device performs multiple functions using a single integrated system. It controls the driving of both liquid-feeding pumps, detects back-flow in either pump's flow path, calculates compensation values, and applies compensations to both pumps' operations. This multi-functional approach achieves accurate gradient control without requiring separate dedicated systems for each function.
Solution Approach 2:
The system merges the back-flow detection and compensation functions into the existing pump control system. The control device that already controls pump driving also performs back-flow detection and compensation calculations, combining multiple functions into a single integrated control mechanism rather than adding separate independent systems.
Data Source
AI summary
In liquid-feeding sections for feeding two types of mobile phases A, B, respectively, actual flow rate measuring sections capable of detecting back-flows are provided in downstream of liquid-feeding pumps, respectively. Control devices control driving of the liquid feeding pumps, respectively, so that measured flow rates by the actual flow rate measuring sections correspond to set flow rates on the liquid-feeding flow paths, respectively. In a case where the set flow rate is zero, when either of the actual flow rate measuring sections detects the back-flow, the corresponding liquid-feeding pump is driven so as to prevent the back-flow.