Chromatography Injector Valve Synchronization with Pump Strokes
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Solution Overview
Problem
High-pressure liquid chromatography systems experience significant pressure drops when introducing a low-pressure sample into a high-pressure solvent stream, leading to undesirable flow deficits and affecting chromatographic outcomes.
Innovation Solution
A method is implemented to synchronize the injection of the sample with the solvent delivery system's pump transfer period, where the number of pump strokes is calculated to deliver the solvent mixture to the injector valve, and the injector valve is switched during a pump stroke boundary when the pump performs pressure control to compensate for pressure drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a low-pressure sample is introduced into a high-pressure solvent stream, then the sample can be injected into the chromatography system, but significant pressure drops occur causing flow deficits and affecting chromatographic outcomes
Solution Approach 1:
The system performs preliminary actions by pre-aspirating the sample into the sample loop with an air gap before the actual injection. This preliminary preparation allows the sample to be ready for injection without requiring high pressure at the moment of introduction, thereby avoiding pressure drops while ensuring the sample is properly positioned for subsequent injection into the high-pressure solvent stream
Solution Approach 2:
An air gap is introduced as an intermediary between the sample and the high-pressure solvent stream. This air gap acts as a buffer that allows the low-pressure sample to be introduced without directly disrupting the high-pressure solvent flow, thereby mitigating the pressure drop effect while still enabling successful sample injection
2Ease of operation
If the injector valve is switched to introduce the sample, then the sample can be injected into the solvent stream, but pressure disturbances occur affecting system stability
Solution Approach 1:
The system employs periodic pump strokes to deliver the solvent stream to the injector valve. By synchronizing the injector valve switching with specific pump stroke boundaries, the system creates a periodic rhythm where sample injection occurs during stable pressure phases (transfer periods), thereby maintaining pressure stability while enabling easy sample injection operation
Solution Approach 2:
The system uses feedback by monitoring pump stroke counts and using this information to determine the optimal timing for injector valve switching. The controller counts pump strokes and triggers injection at predetermined stroke boundaries, creating a feedback-based synchronization mechanism that ensures injection occurs during stable pressure conditions, thus maintaining both ease of operation and pressure stability
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 synchronization effectively reduces pressure disturbances, ensuring reliable and high-quality chromatographic results by compensating for pressure drops during sample injection.
Implementation Method 1
the pump performs pressure control to compensate for a drop in pressure
Data Source
AI summary
A liquid chromatography system includes an autosampler with an injector valve by which a sample at low pressure within a sample loop is introduced into a high-pressure solvent mixture stream. A solvent delivery system includes a pump in fluidic communication with the injector valve of the autosampler to deliver the solvent mixture stream thereto. The solvent delivery system further comprises a processor that calculates a number of strokes of the pump needed to deliver the solvent mixture stream to the injector valve of the autosampler. The processor counts strokes of the pump during delivery of the solvent mixture stream. In response to a stroke count equaling the calculated number of strokes, the processor signals the autosampler to switch the injector valve to introduce the sample to the solvent mixture stream during a pump transfer period within which the pump performs pressure control to compensate for a drop in pressure.