A hydrodynamic injection approach for capillary electrophoresis using rotor–stator valves

Abstract

Sample injection is a critical step in a capillary electrophoresis (CE) analysis. Electrokinetic injection is the simplest approach and is often selected for implementation in portable CE instruments. However, in order to minimize the effect of sample matrix upon the results of a CE analysis, hydrodynamic injection is preferred. Although portable CE instruments with hydrodynamic injection have been reported, injection has always been performed at the grounded end of the capillary. This simplifies fluidic handling but limits coupling with electrochemical detectors and electrospray ionization–mass spectrometry (ESI–MS). We demonstrated previously that injection at the high‐voltage (HV) end of the capillary could be performed using an HV‐compatible rotary injection valve (fixed‐volume injection). However, the mismatch between the bore sizes of the channels on the rotor–stator valve and the separation capillary caused peak tailing and undesired mixing, impairing analytical performance. In this work, we present an HV‐compatible hydrodynamic injection approach that overcomes the issues associated with the fixed‐volume injection approach reported previously. The performance of the CE instrument was demonstrated by analyzing a mixture of 13 amino acids by CE coupled to laser‐induced fluorescence, which showed relative standard deviations for peak area and migration time below 5% and 1%, respectively, for triplicate analysis. Additionally, replicate measurements of a mixture of amino acids, peptides, nucleobases, and nucleosides by CE coupled to electrospray ionization–mass spectrometry (CE–ESI–MS) were performed to evaluate peak tailing, and results were similar to those obtained with a commercial CE–ESI–MS setup.

Submersible Capillary Electrophoresis Analyzer: A Proof-of-Concept Demonstration of an In Situ Instrument for Future Missions to Ocean Worlds

“…These efforts have been largely enabled by miniaturization, integration, and 3D printing . Additionally, the use of rotor–stator valves has facilitated the development of coupled or 2D CE techniques, , which have also been implemented in spaceflight compatible CE systems with different detectors by our team. , …”

“…24 Additionally, the use of rotor−stator valves has facilitated the development of coupled or 2D CE techniques, 25,26 which have also been implemented in spaceflight compatible CE systems with different detectors by our team. 23,27 Numerous methods for chemical and biological investigations of underwater environments have been described in the literature. 28 However, many of these methods primarily focus on collecting samples from remote locations and lack analytical capabilities, 29,30 while others are limited to optical observations and do not require sampling.…”