Chromatographic Sample Injection Using Incremental Mobile-Phase Dilution
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Solution Overview
Problem
Large volume sample injections in liquid chromatography systems using strong solvents lead to peak broadening and distortion, compromising analysis sensitivity and resolution, and traditional sample dilution methods introduce errors and loss.
Innovation Solution
A method and apparatus for injecting a chromatographic sample by introducing incremental volumes of sample and mobile phase, followed by passive mixing, to achieve controlled dilution and focused peak formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large volume of sample is injected into the mobile phase, then the sensitivity of analysis is improved, but peak broadening and distortion occur
Solution Approach 1:
The sample injection process is segmented into multiple smaller incremental injections rather than a single large injection. The injection valve alternates between injecting sample and injecting mobile phase in a cyclic manner, dividing the total sample volume into many small portions that are introduced sequentially into the chromatographic system.
Solution Approach 2:
The injection valve operates in periodic cycles, alternating between a first state where sample is injected and a second state where mobile phase is injected. This periodic switching continues for a specified number of cycles, creating a rhythmic pattern of sample introduction that maintains concentration control while achieving cumulative injection.
2Manufacturing precision
If a smaller volume of sample is injected, then peak broadening is reduced, but sensitivity of analysis decreases
Solution Approach 1:
The method performs preliminary dilution of the sample by alternating sample and mobile phase injections before the sample enters the chromatographic column. This preliminary action of mixing sample with mobile phase in the injection valve prevents peak broadening from occurring during the actual chromatographic separation, while still allowing sufficient total sample mass to be introduced for sensitive detection.
Solution Approach 2:
The mobile phase acts as an intermediary substance that is alternately injected with the sample. It serves as a carrier that dilutes the sample in a controlled manner during the injection process, enabling the sample to be introduced in a form that is compatible with the chromatographic system while maintaining adequate concentration for detection.
3Manufacturing precision
If the sample is diluted offline before injection, then peak distortion is prevented, but operator error and sample loss increase
Solution Approach 1:
The injection valve system performs the dilution function automatically during the injection process itself, without requiring separate offline dilution steps. The system self-regulates by alternating between sample and mobile phase injection, eliminating the need for manual intervention in sample preparation and thereby reducing operator error and sample loss.
Solution Approach 2:
The sample dilution function is merged with the sample injection function. Instead of performing dilution as a separate preliminary step, the dilution process is combined with the injection process by alternating sample and mobile phase delivery through the injection valve, streamlining the overall operation.
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 method ensures well-defined peaks and improved sensitivity by focusing analytes at the column head, reducing solvent interference and peak broadening, while maintaining sample integrity.
Implementation Method 1
The alternating injection of sample and mobile phase allows passive mixing to occur, reducing the need for active mixing mechanisms while achieving homogeneous dilution
Implementation Method 2
As the mobile phase passes through the column, the various components in the sample are differentially retained and thus elute from the column at different times
Implementation Method 3
A detector senses the separated components eluted from the column and generates an output signal or chromatogram from which the identity and quantity of the analytes can be determined
Data Source
Figure 1~2
Figure 3A~3C
Figure 4
AI summary
A method for diluting a sample upon injection into a chromatographic system flow, comprising: a) injecting an incremental volume of a sample into a chromatographic system flow, the sample comprising at least one analyte dissolved in a solvent; b) providing an incremental volume of a mobile phase into the chromatographic system flow; and repeating steps a) and b) until a total volume of stored sample is injected into the chromatographic system flow, wherein a dilution ratio of the injected sample equals the sum of the incremental volumes of the sample and the mobile phase divided by the sum of the incremental volumes of the sample.