Chip-based solid phase extraction

Tan, A., Benetton, S., and Henion, J. D. (2003). Chip-based solid-phase extraction pretreatment for direct electrospray mass spectrometry analysis using an array of monolithic columns in a polymeric substrate. Anal. Chem. 75, 5504—5511. 

Figure 5.8 Schematic representation of a chip-based solid phase extraction-MEKC device, (a) Layout of the entire device and (b) expanded view of the extraction region of the device. The dotted lines represent the direction of fluid flow during extraction the solid lines signify flow during elution/injection (Narrow channels are 55 pm wide, column chamber is 210 pm wide, with all channels 15 pm deep.) [87].

Oleschuk, R. D., L. L. Shultz-Lockyear, Y. Ning, and D. J. Harrison. Trapping of bead-based reagents within microfluidic systems On-chip solid-phase extraction and electrochromatography. Anal. Chem. 72, 585-590 (2000). 

Pushing detection limits of nitroaromatic explosives into the parts per trillion (ppt) level requires sample preconcentration. Collins and coworkers used solid-phase extraction (SPE) of explosives from sea water which was followed by rapid on-chip separation and detection [18]. Explosives were eluted from SPE column by acetonitrile and were injected in the microchip separation channel. Lab-on-a-chip analysis was carried out in nonaqueous medium. The mixed acetonitrile/methanol separation buffer was used to produce the ionized red-colored products of TNT, TNB and tetryl [27,28]. The chemical reaction of the bases (hydroxide and methoxide anions) with trinitroaromatic explosives resulted in negatively charged products, which were readily separated by microchip... 

DNA extraction and purification were traditionally accomplished using organic extraction and ultracentrifugation-based procedures, which are both time-consuming and not easily transferable to the microscale. Newer methods employ solid-phase extraction (SPE) on silica surfaces, glass fibers, modified magnetic beads, and ion-exchange resins—techniques that save time and are also more amenable to chip applications. 

Zip-Tips (Billerica, Massachusetts) are automation-compatible pipette tips that contain a chromatography sorbent held in the tip with a membrane. These tips allow for microscale solid-phase extraction to purify and preconcentrate samples. Some examples of this approach are sample cleanup step with isoelectric point (pl)-based fractionation of peptides prior to matrix-assisted laser-desorption/short ionization (MALDl) spotting [29] or chip-based ESI analysis of colon adenocarcinoma (Caco-2) screening samples [30]. The preliminary results of induction-based fluidics in which nanoliter volumes... 

Fig. 3 Schematic workflow of porous silicon-ISET iMALDI top (I), antibody-immobilized porous silicon was used to capture the antigen angiotensin I bottom (II), RP solid-phase extraction sample preparation protocol on the ISET chip was used to purify and reconcentrate the elution followed by MALDI MS deteetion (Yan et al. 2011) (Reprinted with permission from Analytical Chemistry, 83, Yan, Ahmad-Tajudin, Bengtsson, Xiao, Laurell, Ekstrom, Noncovalent antibody immobilization on porous silieon eombined with miniaturized solid-phase extraction SPE) for array based immunoMALDI assays, 4942-4948. Copyright 2011 Ameriean Chemieal Society)...

A solid-phase extraction technique coupled with a chip-based flow injection system was introduced to determine vitamin Bj by spectrofluorimetry (Zhu et al. 

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