Switching Unit for HPLC Sampling Path Pressure Control
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Solution Overview
Problem
In high-performance liquid chromatography (HPLC), fluidic coupling and decoupling of sampling volumes with high-pressure paths cause pressure perturbations, leading to noise in chromatograms and potential damage to chromatographic columns, which existing 'make-before-break' schemes partially address but not fully.
Innovation Solution
A switching unit is configured to selectively fluidically couple a sampling volume, sampling drive, and mobile phase drive with the separating device, maintaining continuous flow and pressure control during switching states, allowing for both Feed-Injection and flow-through sample introduction configurations, thereby minimizing pressure effects and ensuring column longevity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If fluidic coupling and decoupling of sampling volume with high-pressure path is performed, then sample introduction is achieved, but pressure perturbations occur causing noise in chromatograms and potential damage to columns
Solution Approach 1:
The switching unit is configured to fluidically couple the sampling volume with the mobile phase drive and separating device before completely decoupling the mobile phase drive from the separating device. This preliminary coupling ensures that the separating device already has an active fluidic connection to a pressure source during the transition, preventing pressure drops and maintaining stable flow conditions throughout the switching process.
Solution Approach 2:
The sampling volume acts as an intermediary component between the mobile phase drive and the separating device during switching operations. By coupling the sampling volume to the separating device while the mobile phase drive is being switched, the system maintains a continuous pressure buffer and flow path, preventing direct pressure perturbations from reaching the separating device and column.
2Reliability
If make-before-break switching scheme is used to maintain fluidic coupling during switching, then pressure stability is improved, but device complexity increases due to extended stator grooves in rotational valves
Solution Approach 1:
The switching operation is divided into distinct sequential steps: first coupling the sampling volume with the mobile phase drive, then coupling it with the separating device, and finally decoupling the mobile phase drive. This segmentation of the switching process into manageable stages allows for controlled transitions that maintain pressure stability without requiring complex extended stator grooves, simplifying the valve structure while achieving the make-before-break effect.
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 solution maintains continuous fluidic coupling and controlled flow during sample introduction, reducing pressure perturbations and extending the lifespan of chromatographic columns by actively managing pressure and flow, resulting in improved resolution and reliability of HPLC measurements.
Implementation Method 1
The separating device is fluidically coupled with at least one of the mobile phase drive and the sampling drive during switching from the sample load configuration to the decouple configuration, and during switching from the decouple configuration to the sample introduction configuration. This allows maintaining a fluidic coupling of the separating device with at least one upstream unit such as the mobile phase drive, the sampling drive, the sampling volume. The flow to the separating device can be always maintained and may be controlled to provide a flow towards the separating device
Implementation Method 2
The mobile phase, for example a solvent, is pumped under high pressure typically through a chromatographic column containing packing medium. As the sample is carried through the column by the liquid flow, the different compounds, each one having a different affinity to the packing medium, move through the column at different speeds
Implementation Method 3
For liquid separation in an HPLC system, a mobile phase comprising a sample fluid (e.g. a chemical or biological mixture) with compounds to be separated is driven through a stationary phase (such as a chromatographic column packing), thus separating different compounds of the sample fluid
Implementation Method 4
In a sample load configuration, the switching unit is configured for fluidically coupling the sampling volume and the sampling drive, for moving the fluidic sample into the sampling volume
Implementation Method 5
In a decouple configuration, the switching unit is configured for fluidically coupling the sampling volume between the sampling drive and the separating device, while the mobile phase drive is fluidically decoupled from the separating device
Data Source
AI summary
A switching unit is configured for selectively fluidically coupling a sampling volume, a sampling drive, a mobile phase drive, and a separating device. In a sample load configuration, the switching unit is configured for fluidically coupling the sampling volume and the sampling drive, for moving the fluidic sample into the sampling volume. In a decouple configuration, the switching unit is configured for fluidically coupling the sampling volume between the sampling drive and the separating device, while the mobile phase drive is fluidically decoupled from the separating device. In a sample introduction configuration, the switching unit is configured for fluidically coupling the mobile phase drive, the sampling volume, and the separating device for introducing at least an amount of the fluidic sample stored in the sampling volume into the mobile phase for fluid separation by the separating device.