Flow Control Assembly for Solid Phase Extraction
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Solution Overview
Problem
Micro Extraction by Packed Sorbent (MEPS) is bidirectional, lacking control over the direction of sample and buffer delivery across the solid phase sorbent bed, leading to potential dilution and carryover issues.
Innovation Solution
A flow control assembly that allows selective aspiration or delivery of fluids across the solid phase sorbent, providing independent flow paths for the sample and elution solvent, enabling control over the direction of liquid flow and bypassing the sorbent bed when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If bidirectional flow is used in MEPS, then the device is simple and easy to operate, but the sample becomes diluted and carryover occurs
Solution Approach 1:
The flow control assembly divides the fluid flow into separate paths: a first path through the solid phase sorbent bed and a second path bypassing the sorbent bed. This segmentation allows independent control of sample loading (through the sorbent) and elution solvent delivery (bypassing the sorbent), preventing dilution while maintaining operational simplicity
Solution Approach 2:
The flow control assembly uses a movable member that can selectively switch between different flow paths. This dynamic control allows the system to adapt flow directions based on the extraction stage (loading vs. elution), optimizing sample concentration while maintaining ease of operation through a single movable component
2Device complexity
If bidirectional flow is used in MEPS, then the device structure is simple, but control over flow direction is lost
Solution Approach 1:
The flow control assembly segments the flow paths into a first path through the sorbent bed and a second path bypassing it. This segmentation provides independent flow control for sample loading and elution, enhancing adaptability while keeping the device structure relatively simple
Solution Approach 2:
The flow control assembly acts as an intermediary component between the syringe barrel and the sorbent bed, providing selective communication between different flow paths. This intermediary device enables precise flow direction control without requiring complex valve mechanisms or multiple separate devices
3Reliability
If elution solvent is applied from the top of the absorbent bed, then sample carryover is minimized, but the device requires additional flow control structure
Solution Approach 1:
The flow control assembly segments the elution solvent delivery path separate from the sample loading path. The elution solvent flows through the second path that bypasses the sorbent bed, then re-enters through the bottom, applying solvent from the bottom rather than top. This segmentation achieves sample purity while adding minimal structural complexity
Solution Approach 2:
Instead of applying elution solvent from the top of the sorbent bed (conventional approach), the flow control assembly inverts the approach by delivering solvent through the bypass path and re-entering at the bottom of the bed. This inversion minimizes sample carryover while the modular design keeps the added complexity minimal
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 minimizes dilution, reduces carryover, and allows for more efficient analyte concentration, enabling direct infusion into detectors for enhanced assay sensitivity and potentially using smaller sorbent particles for improved binding efficiency.
Implementation Method 1
a first passage arranged to be in fluid communication with the needle bore at its inner end and to locate a solid phase sorbent that contacts fluid traversing the first passage and adsorbs predetermined species
Implementation Method 2
a valve arrangement for selectively communicating the barrel chamber with the first passage and thereby with the needle bore or with the second fluid port for facilitating selective aspiration or delivery of fluid
Data Source
AI summary
A flow control assembly for use in preparation of samples for analysis by solid phase extraction includes a housing assembly having a first passage communicating with a needle bore and locating a solid phase sorbent, a second fluid port, and a valve for selective aspiration or delivery of fluid across a solid phase sorbent, or bypassing the solid phase sorbent. Independent flow paths are provided for a sample via the needle, and of the elution solvent via a separate port. The valve includes relatively slideable first and second members, the second member including an elongate shank that is relatively reciprocably slideable for effecting selective aspiration or delivery of fluid between first and second relative positions. A third fluid port may be provided communicating with the elongate second passage for selective fluid communication with a port in a shank when the shank is at the second relative position.