Microfluidic Picoliter-Scale Translational Spontaneous Sample Introduction for High-Speed Capillary Electrophoresis

Abstract

A novel microfluidic picoliter-scale sample introduction approach was developed by combining the spontaneous injection approach with a capillary electrophoresis (CE) system based on a short capillary and slotted-vial array. A droplet splitting phenomenon at the capillary inlet end during the spontaneous sample introduction process was observed for the first time. On the basis of this phenomenon, a translational spontaneous injection approach was established to reduce sample injection volumes to the sub-100 pL range. A versatile high-speed capillary electrophoresis (HSCE) system was built on the basis of this sample injection approach with separation performance comparable to or even better than those reported in microfluidic chip-based CE systems. The HSCE system was composed of a short fused-silica capillary and an automated sample introduction system with slotted sample and buffer reservoirs and a computer-programmed translational stage. The translational spontaneous sample injection was performed by linearly moving the stage, allowing the capillary inlet first to enter the sample solution and then removing it. A droplet was left at the tip end and spontaneously drawn into the capillary by surface tension effect to achieve sample injection. The stage was continuously moved to allow the capillary inlet to be immersed into the buffer solution, and CE separation was performed by applying a high voltage between the buffer and waste reservoirs. With the use of the novel system, high-speed and efficient capillary zone electrophoresis (CZE) separation of a mixture of five fluorescein isothiocyanate (FITC) labeled amino acids was achieved within 5.4 s in a short capillary with a separation length of 15 mm, reaching separation efficiencies up to 0.40 microm plate height. Outstanding peak height precisions ranging from 1.2% to 3.7% RSD were achieved in 51 consecutive separations. By extension of the separation length to 50 mm, both high-speed and high-resolution CZE separation of eight FITC-labeled amino acids could be obtained in less than 21 s with theoretical plates ranging from 163,000 to 251,000 (corresponding to 0.31-0.20 microm plate heights). The present HSCE system also allowed fast chiral separations of FITC-labeled amino acids under micellar electrokinetic chromatography (MEKC) mode within 6.5 s.

High‐speed separation of proteins by sodium dodecyl sulfate‐capillary gel electrophoresis with partial translational spontaneous sample injection

“…1, which is similar to that reported previously [17], except that 0.2-mL slotted plastic centrifuge tubes were used for containing sample and buffer solutions instead of the slotted sandwich reservoirs. Briefly, the capillary was fixed on a glass plate with a hole (ca.…”

“…However, for a HSCE system based on a short capillary with an effective separation length of a few centimeters, narrow sample plugs o100 mm are usually essential to ensure sufficient separation efficiency. The translational spontaneous injection technique offers a promising way to obtain narrow sample plugs required in HSCE systems [17].…”

“…This approach was successfully applied in the separation of amino acids under CZE and MEKC modes [17]. In this study, we investigated the applicability of this approach in high-speed separation of proteins under SDS-CGE mode, and developed a partial translational spontaneous injection method suitable for high-viscosity buffer used in SDS-CGE systems.…”

A miniaturized spatial temperature gradient capillary electrophoresis system with radiative heating and automated sample introduction for DNA mutation detection

“…It has been demonstrated that short capillary-based CE systems can achieve high-speed and high-efficiency separation [32,33]. In this study, a 14 cm long Teflon AF-coated fused silica capillary served as the separation channel to ensure rapid DNA separation.…”

An Automated Fluid-transport Device for a Microfluidic System

“…22 Subsequently, they made extensive improvements on a slotted-vial array sample introduction device, and achieved the goal of sampling automation on a microfluidic platform. [23][24][25][26] All of the studies described above, mainly focused on sample introduction. Yet, there have been distinct requirements to fulfill multiple functions, including chip cleaning and activation, since these procedures are prerequisites for chip electrophoresis.…”