Recent progress of online sample preconcentration techniques in microchip electrophoresis

Abstract

Microchip electrophoresis (MCE) has been advanced remarkably by the applications of several separation modes and the integration with several chemical operations on a single planer substrate. MCE shows superior analytical performance, e.g., high-speed analysis, high resolution, low consumption of reagents, and so on, whereas low-concentration sensitivity is still one of the major problems. To overcome this drawback, various online sample preconcentration techniques have been developed in MCE over the past 15 years, which have successfully enhanced the detection sensitivity in MCE. This review highlights recent developments in online sample preconcentration in MCE categorized on the basis of "dynamic" and "static" methods. The dynamic techniques including field amplified stacking, ITP, sweeping, and focusing have been easily applied to MCE, which provide effective enrichments of various analytes. The static techniques such as SPE and filtration have also been combined with MCE. In the static techniques, extremely high preconcentration efficiency can be obtained, compared to the dynamic methods. This review provides comprehensive tables listing the applications and sensitivity enhancement factors of these preconcentration techniques employed in MCE.

Recent Progress of On-line Sample Preconcentration Techniques in Microchip Electrophoresis

“…8 In these applications, LIF detection has been mainly employed, so that a fluorescence labeling of analytes have been accompanied. In the recent years, on the other hand, universal capacitively coupled contactless conductivity detection (C 4 D) schemes and EC detectors have been combined with FASS-MCE to enhance the sensitivity for food dyes, 32 inorganic anions, 33 amines, 34 tetracycline antibiotics, 35 and endocrine disruptors.…”

“…Besides this, some novel sample preconcentration techniques utilizing specific characteristics of microchips have appeared in MCE. 8 The on-line sample preconcentration techniques for MCE have four classifications: preconcentration by analyte velocity change in two or three discontinuous solutions system, focusing, [9][10][11][12][13][14][15][16][17][18][19][20] solid phase extraction, [21][22][23] and electrokinetic trapping (filtering). [24][25][26][27] Among them, novel focusing and electrokinetic trapping techniques have been exhaustively investigated in the recent decade.…”

Integrated continuous flow polymerase chain reaction and micro‐capillary electrophoresis system with bioaffinity preconcentration

“…However, it is difficult to find suitable leading and terminating electrolytes for isotachophoresis [40]. On-chip sample injection techniques for preconcentration prior to mCE (stacking and sweeping methods) have been reviewed extensively [41].…”

A microfabricated CE chip for DNA pre‐concentration and separation utilizing a normally closed valve

“…Offline sample pre-concentration usually requires a tedious experimental protocol. Therefore, online sample pre-concentration techniques have been extensively studied in recent years [12][13][14]. A variety of online sample pre-concentration techniques have been reported in the literature, including fieldamplified sample stacking [15][16][17], sweeping techniques [18][19][20][21], dynamic pH junction techniques [22,23], isotachophoresis [24,25], and solid-phase extraction technology [26,27].…”