On-Line Coupling of Chip-Electrochromatography and Ion Mobility Spectrometry

Abstract

We report the first hyphenation of chip-electrochromatography (ChEC) with ion mobility spectrometry (IMS). This approach combines the separation power of two electrokinetically driven separation techniques, the first in liquid phase and the second in gas phase, with a label-free detection of the analytes. For achieving this, a microfluidic glass chip incorporating a monolithic separation column, a nanofluidic liquid junction for providing post-column electrical contact, and a monolithically integrated electrospray emitter was developed. This device was successfully coupled to a custom-built high-resolution drift tube IMS with shifted potentials. After proof-of-concept studies in which a mixture of five model compounds was analyzed in less than 80 s, this first ChEC−IMS system was applied to a more complex sample, the analysis of herbicides spiked in the wine matrix. The use of ChEC before IMS detection not only facilitated the peak allocation and increased the peak capacity but also enabled analyte quantification. As both, ChEC and IMS work at ambient conditions and are driven by high voltages, no bulky pumping systems are needed, neither for the hydrodynamic pumping of the mobile phase as in high-performance liquid chromatography nor for generating a vacuum system as in mass spectrometry. Accordingly, the approach has great potential as a portable analytical system for field analysis of complex mixtures.

Coupling Droplet Microfluidics with Ion Mobility Spectrometry for Monitoring Chemical Conversions at Nanoliter Scale

“…In earlier work, volatile MS-compatible ammonium-based solutions were successfully used as reaction media for wholecell biocatalysis when performing ESI-MS measurements. 35 However, in compliance with previous results, 38 this led to a severe reduction of the IMS sensitivity. In contrast, in NaOAc solution, the analytes showed good ionization efficiencies, which is why it was chosen for further experiments.…”

“…■ RESULTS AND DISCUSSION Development of an ESI-IMS Platform for the Detection of Droplet Microfluidics. Encouraged by our experience with the coupling of droplet microfluidics with mass spectrometric detection, 18,33,35,37 as well as the recently realized coupling of chip chromatography with IMS, 38,39 we aimed in this work to explore the potential of IMS for droplet analysis. Therefore, a custom-built drift tube IMS with shifted potentials 62 was employed as a detector, which was modified with two SST inlets.…”

“…For IMS analysis, a custom-built drift tube IMS with shifted potentials was employed to provide ground potential at the inlet, as it was previously described in detail. ,− The instrument was operated at ambient conditions with purified nitrogen as drift gas (300 mL/min). The IMS inlet was adjusted with two stainless steel (SST) inlets with a 6 and 5 mm diameter hole, maintaining an electric field of 650 V/cm.…”

“…Recently, we have shown that IMS can be an interesting alternative detection technique in chip-based separations. , Similar to MS, IMS is based on the separation of gaseous ions. Most of these stand-alone IMS systems are operated at ambient pressure, which translates into significantly less instrumental complexity compared to high-vacuum MS instruments.…”

Development of Microchip Isotachophoresis Coupled with Ion Mobility Spectrometry and Evaluation of Its Potential for the Analysis of Food, Biological and Pharmaceutical Samples

“…The biggest obstacle in combining these two techniques is the necessity to transfer analytes from liquid to the gaseous phase. Therefore, only a few attempts to combine IMS with CE [ 13 , 15 , 16 , 17 ], MCE [ 18 ] or chip-based electrochromatography [ 19 ] were made.…”