Variable Ratio Flow Splitter for Supercritical Fluid Chromatography
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Solution Overview
Problem
Conventional flow splitters are ineffective in preparative supercritical fluid chromatography (SFC) due to unpredictable split behavior caused by pressure and viscosity variations, phase changes, and evaporative solvent loss, which results in precipitation of solutes and plugging issues, especially at high pressures and flow rates.
Innovation Solution
A high split ratio flow splitter with a passive restrictor network comprising alternating stages of flow splitting and dilution, featuring pressure balancing and multiple dilution stages to maintain consistent physical properties and achieve high dilution ratios, capable of operating at pressures up to 300 bar and handling both HPLC and SFC mobile phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional flow splitters are used in preparative supercritical fluid chromatography, then the device structure is simple, but the split behavior becomes unpredictable due to pressure and viscosity variations, phase changes, and evaporative solvent loss
Solution Approach 1:
The flow splitter is divided into multiple sequential stages, each performing a portion of the total split ratio. This segmentation allows each stage to operate within a controlled pressure and flow range, preventing phase changes and ensuring predictable split behavior while achieving high overall split ratios through multiplication of individual stage ratios.
Solution Approach 2:
Dilution solvents are introduced as intermediary substances between the supercritical mobile phase and the detector. These intermediaries facilitate gradual pressure reduction and prevent direct phase changes by mixing the supercritical phase with compatible solvents, thereby maintaining flow stability and preventing solute precipitation.
2Quantity of substance
If high split ratios are achieved through single-stage splitting, then the device complexity is low, but the dilution ratio is insufficient to reduce solute concentrations to levels suitable for analytical detectors
Solution Approach 1:
The dilution process is segmented into multiple stages, with each stage introducing a portion of the total dilution. This allows the system to achieve very high overall dilution ratios (e.g., 10,000:1 or greater) by multiplying the dilution factors of individual stages, while keeping each stage's complexity manageable.
Solution Approach 2:
The system transitions from a single-dimension splitting approach to a multi-dimensional approach by combining split ratio multiplication across stages with dilution ratio multiplication. This allows simultaneous achievement of high split ratios and high dilution ratios through the combined effect of multiple operational dimensions.
3Stability of the object's composition
If pressure is maintained high to prevent phase changes, then phase stability is improved, but the ability to deliver flow to atmospheric pressure detectors is compromised
Solution Approach 1:
The pressure reduction process is segmented into multiple gradual steps across different stages, rather than a single abrupt drop. Each stage reduces pressure by a manageable amount while introducing dilution solvent, preventing sudden phase changes and allowing the system to transition from high pressure to atmospheric pressure while maintaining flow stability.
Solution Approach 2:
The system gradually changes physical parameters (pressure, composition, temperature) across multiple stages rather than making abrupt changes. By incrementally adjusting these parameters and introducing dilution solvents, the system maintains phase stability during the transition from high-pressure supercritical conditions to atmospheric pressure detector conditions.
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 solution achieves split ratios of over 1,000,000:1 and dilution ratios of up to 10,000:1, effectively reducing solute concentrations to levels suitable for analytical detectors, while maintaining consistent performance across varying pressures and viscosities, preventing phase changes and plugging, and ensuring efficient separation in both HPLC and SFC systems.
Implementation Method 1
a first flow restrictor in said first main flowstream and a second flow restrictor in said second main flowstream, said first and second flow restrictors having different pressure differentials across said restrictors
Implementation Method 2
laminar flow tubular restrictors
Implementation Method 3
passive restrictor network comprised of one or more alternating stages of flow splitting and dilution
Implementation Method 4
flow splitting and dilution occur serially in the split flowstream
Data Source
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AI summary
A splitter (60) for a pressurized primary flowstream (64) comprises a first splitting stage (66) that divides the primary flowstream between a major and a minor split flowstream by means of a first (68) and a second (70) restrictive flow element; a first dilution stage (72) that combines a dilution flow source (80) with the minor split flowstream to create a diluted minor flowstream (74);a second splitting stage (88) that divides the diluted minor flowstream between secondary major (76) and minor diluted flowstreams by means of a third restrictive element (90) in the secondary minor diluted flowstream; and a second dilution stage (92) wherein a conditioning flow source (94) conditions the secondary minor diluted flowstream after the third restrictive element (90) prior to outlet of the secondary minor diluted flowstream from the splitter. One embodiment further comprises a pressure balancing stage (78) which recombines the major split and the secondary major diluted flowstreams to an exit flowstream in fluidic communication with a backpressure regulator (86).