Split-Flow Modulator for Narrow GC×GC Reinjection Pulses
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Solution Overview
Problem
Conventional gas chromatography methods face challenges in increasing separating power without disproportionately increasing analysis time, and existing modulators for comprehensive two-dimensional gas chromatography suffer from inefficiencies such as inconsistent fraction transfer, high gas consumption, and wide reinjection widths, which affect the detectability of low concentration analytes.
Innovation Solution
A re-sampling device for two-dimensional gas chromatography that includes a modulator and upstream or downstream splitters to split the effluent, allowing for consistent fraction transfer and reduced gas consumption, with accumulating loops and auxiliary gas supply to manage reinjection pulses, ensuring precise and efficient transfer to the secondary column.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional GC analysis is used to increase separating power, then the number of separable components increases, but the analysis time increases disproportionally
Solution Approach 1:
The patent implements comprehensive two-dimensional gas chromatography (GC×GC) which segments the separation process into two independent dimensions: a primary column for initial separation and a secondary column for orthogonal separation. A modulator divides the primary column effluent into multiple narrow reinjection pulses that are sequentially injected into the secondary column. This segmentation allows complex mixtures to be separated across two dimensional spaces, increasing the number of separable components by more than a factor of 10 without proportionally increasing analysis time.
2Productivity
If snapshot modulation is used to transfer effluent to secondary column, then modulation period is divided into sub-intervals, but consistent fraction transfer cannot be achieved
Solution Approach 1:
The patent employs periodic modulation where the modulator systematically switches between different flow paths at regular intervals. During each modulation period, the system alternates between transferring effluent to the secondary column and directing it to waste. This periodic action, combined with the accumulating loop mechanism, ensures that a consistent fraction of the primary eluite is transferred to the secondary column during each cycle, achieving both high productivity and reliable transfer consistency.
3Measurement precision
If full transfer modulation is used to accumulate entire primary effluent, then complete eluite transfer is achieved, but high gas consumption occurs
Solution Approach 1:
The patent implements a controlled transfer mechanism where only a fraction of the primary effluent is transferred to the secondary column during each modulation cycle, while the remainder is directed to waste. The accumulating loop accumulates the primary eluite and transfers it as narrow reinjection pulses to the secondary column, rather than transferring the entire effluent continuously. This partial transfer approach maintains sufficient analyte concentration for detection while significantly reducing the gas consumption associated with full transfer modulation.
4Loss of time
If snapshot modulation with short sampling period is used, then analysis time is reduced, but reinjection pulse sharpness is limited
Solution Approach 1:
The patent uses an accumulating loop that accumulates the primary eluite during the modulation period before transfer to the secondary column. This preliminary accumulation allows the system to prepare a concentrated sample band in advance, which is then transferred as a sharp reinjection pulse. The accumulating loop acts as a buffer that decouples the sampling period duration from the reinjection pulse width, enabling short sampling periods for rapid analysis while maintaining sharp reinjection pulses for high chromatographic precision.
Data Source
AI summary
A re-sampling device for two-dimensional gas chromatography includes a modulator and at least one of a first splitter disposed upstream from the modulator and configured to split an effluent from a primary column and deliver a portion of the effluent to waste and a portion of the effluent to the modulator, or a second splitter disposed downstream from the modulator and configured to split the effluent to deliver a portion of the effluent to waste and a portion of the effluent to a secondary column.