Polymeric Microchip for the Simultaneous Determination of Anions and Cations by Hydrodynamic Injection Using a Dual-Channel Sequential Injection Microchip Electrophoresis System

Abstract

A dual-channel sequential injection microchip capillary electrophoresis system with pressure-driven injection is demonstrated for simultaneous separations of anions and cations from a single sample. The poly(methyl methacrylate) (PMMA) microchips feature integral in-plane contactless conductivity detection electrodes. A novel, hydrodynamic "split-injection" method utilizes background electrolyte (BGE) sheathing to gate the sample flows, while control over the injection volume is achieved by balancing hydrodynamic resistances using external hydrodynamic resistors. Injection is realized by a unique flow-through interface, allowing for automated, continuous sampling for sequential injection analysis by microchip electrophoresis. The developed system was very robust, with individual microchips used for up to 2000 analyses with lifetimes limited by irreversible blockages of the microchannels. The unique dual-channel geometry was demonstrated by the simultaneous separation of three cations and three anions in individual microchannels in under 40 s with limits of detection (LODs) ranging from 1.5 to 24 μM. From a series of 100 sequential injections the %RSDs were determined for every fifth run, resulting in %RSDs for migration times that ranged from 0.3 to 0.7 (n = 20) and 2.3 to 4.5 for peak area (n = 20). This system offers low LODs and a high degree of reproducibility and robustness while the hydrodynamic injection eliminates electrokinetic bias during injection, making it attractive for a wide range of rapid, sensitive, and quantitative online analytical applications.

Application of capacitively coupled contactless conductivity as an external detector for zone electrophoresis in poly(dimethylsiloxane) chips

“…The obtained LOD and theoretical plate number values, the applicability of the analysis for various types of samples all demonstrate that the PDMS chips with C 4 D are suitable for the analysis of inorganic anions in real samples. The LOD values (3.66–14.7 μM) obtained in our microfluidic system were in similar range (2.5–24 μM) reported by others . The assembled portable analytical system can be arranged on a laboratory tray or in a medium‐sized briefcase with all accessories (its weight less than 3 kg), therefore it can be easily moved and carried (Supporting Information Fig.…”

Concurrent determination and separation of inorganic cations and anions in microchip electrophoresis with precisely controlled high‐voltage

“…The RSDs of both microchips were slightly higher compared with those obtained in previous studies that had employed simultaneous and separations of anions and cations in ME . The main reason may be that the injection method of our system was not automated enough.…”

“…reported on a dual‐end opposite injection CE microchip for the simultaneous detection, such microchip needed a dual injection structure and double sample reagent consumption . In the ME‐C 4 D system of Gaudry et al., two separation channels and two C 4 D detectors were needed, although the simultaneous determination can be implemented, the microchip structure and detection system were very complicated . Thus, it is significant to find a method for the concurrent determination of cations and anions in ME using only one injection channel, one separation channel and one C 4 D detector within a short period of time.…”

Online Comprehensive Two-Dimensional Ion Chromatography × Capillary Electrophoresis

“…While improving the transfer efficiency is certainly the way forward to exploit the potentials of IC×CE, the chip-based SI-CE approach with in-plane detection previously introduced in our group 16 offers the possibility of integrating the second dimension as one of the components in IC detector compartment.…”