Solid-Phase Extraction in Segmented Flow

Abstract

Two-phase flow systems are increasingly popular for miniaturized, high-throughput performance of analytical or chemical reactions. In this contribution, we extend a previously described method that allows to increase the range of applications of heterogeneous reactions in two-phase flow, i.e., reactions that rely on isolation and purification of the compound of interest for downstream analysis. Our concept is based on liquid plugs, which serve as miniaturized compartments for the analytical reactions. Purification of the target compound is achieved by extracting the analyte from the aqueous compartments using magnetic beads as solid carriers. In the present paper, we elucidate the influence of parameters such as the polarity of the liquid/liquid and solid/liquid interfaces, the magnetic forces and the fluidic conditions onto the extraction performance. The conditions for reliable extraction and purification of the target compounds are determined. Furthermore, we investigate how to facilitate breaking of the plugs through reduction of the surface tension of the solid/liquid interface. When a lower surface tension is employed, a smaller number of beads is required for the extraction process, which implies a higher sensitivity of the device. In addition, we generate channels with different surface chemistries, which are able to manipulate the flow of the two immiscible liquids. We describe a very simple way to generate such devices and show that we can achieve a transition from segmented flow of plugs to a side-by side flow of the two immiscible liquids, a key requirement for the purification of the compounds.

Breaking the Interface: Efficient Extraction of Magnetic Beads from Nanoliter Droplets for Automated Sequential Immunoassays

“…Thus, we conclude that this setup does not allow extracting beads at a concentration of 1 mg/mL or lower. This is in agreement with earlier studies. , …”

“…One way to overcome this challenge is to avoid extraction altogether. This can be achieved by merging the aqueous droplets with the continuous aqueous phase, thus avoiding the need for particles to pass through the water–oil interface . This strategy enables the analysis of low amounts of beads at the expense of losing the droplets in the continuous phase.…”

“…This can be achieved by merging the aqueous droplets with the continuous aqueous phase, thus avoiding the need for particles to pass through the water−oil interface. 10 This strategy enables the analysis of low amounts of beads at the expense of losing the droplets in the continuous phase. This approach, however, excludes the option to analyze the droplet phase after the extraction or to reuptake the magnetic beads into another droplet.…”

Solid-phase extractions in flow analysis

“…The scarce number of SPE applications in segmented-flow analysis is due to the drawbacks of introducing air-bubbles in the sorbent mini-column. This limitation can be overcome by applying a novel extraction principle relying on functionalized magnetic beads (Rendl et al 2014, Schönberg et al 2015. The beads are added to every aqueous sample segments, yielding highly reproductive suspensions.…”

A two-magnet strategy for improved mixing and capture from biofluids

“…[1][2][3] Flow-through systems deliver magnetic particles via carrier fluid motion, where magnetic beads are suspended in a fluid and captured by a magnetic field. [4][5][6][7][8][9][10] To overcome the challenges inherent in fluid-based delivery of magnetic beads, an alternative technology based on static prearrayed fluid cartridges has been developed where magnetic beads are again used as a mobile substrate, but transported by magnetic entrainment rather than bulk fluid flow. In these designs, each chamber is used to perform a single processing or reaction step and instead of pumping different fluids past immobilized ligands, surface-functionalized magnetic beads are carried by a magnetic field from fluid chamber to fluid chamber.…”