How to Improve the Resolving Power of Compact Electrospray Ionization Ion Mobility Spectrometers

Abstract

Every drift tube ion mobility spectrometer (IMS) has an optimum drift voltage to reach maximum resolving power. This optimum depends, among other things, on the temporal and spatial width of the injected ion packet and the pressure within the IMS. A reduction of the spatial width of the injected ion packet leads to improved resolving power, higher peak amplitudes when operating the IMS at optimum resolving power, and thus a better signal-to-noise ratio despite the reduced number of injected ions. Hereby, the performance of electrospray ionization (ESI)-IMS can be considerably improved. By setting the ion shutter opening time to just 5 μs and slightly increasing the pressure, a high resolving power R P > 150 can be achieved with a given drift length of just 75 mm. At such high resolving power, even a mixture of the herbicides isoproturon and chlortoluron having similar ion mobility can be well separated despite short drift length.

Coated Blade Spray Ion Mobility Spectrometry

“…To further increase sensitivity, longer extraction times and higher drift voltages can be selected. 28 Furthermore, the ionization efficiency might be further improved by suitable additives, as has been shown in previous publications on ESI-IMS and ESI-MS. 37,39−41 Further improving CBS-IMS and investigating additives in the desorption solution for better desorption and ionization efficiency will be carried out in subsequent work. and spiked with 1 mg/L ketamine (middle) and 8 mg/L ketamine (bottom), extracted via coated blades and detected via CBS-IMS.…”

“…In this work, we used our ion mobility spectrometer with 75 mm drift tube length. A detailed description can be found elsewhere. , Here, the ions are generated by electrospray ionization directly from the coated blades (CB-HLB blades, Restek GmbH, Bad Homburg, Germany) within a desolvation region of 50 mm length. The coated blades are made of stainless steel and are 42 mm long and 10 mm of the tip is coated with a hydrophilic–lipophilic balanced (HLB) sorbent.…”

“…A detailed description can be found elsewhere. 28,29 Here, the ions are generated by electrospray ionization directly from the coated blades (CB-HLB blades, Restek GmbH, Bad Homburg, Germany) within a desolvation region of 50 mm length. also adds a defined volume of the desorption solvent to the coated area before turning on the ESI voltage; here, we use 20 μL of a mixture of 20% water, 80% methanol, and an addition of 0.1% formic acid.…”

“…In particular, the advantages of CBS can be well exploited in IMS. In this work, we focus on coupling CBS with our previously described ESI-IMS. , The ion mobility spectrometer has a drift length of only 75 mm and provides a high resolving power of R P = 100. Here, a first characterization of CBS-IMS is presented.…”

Electrospray Ion Mobility Spectrometer Based on Flexible Printed-Circuit Board Electrodes with Improved Resolving Power

“…This was achieved mainly by using a purpose-built instrument with a drift tube of 15 cm length, which is slightly longer than the typical 10 cm, and the use of a very short injection time of 5 μs. Very recently, Zimmermann’s group also demonstrated a resolving power of 155 for an ESI–IMS . This was achieved in a drift tube of 75 mm length by using a short injection time of 5 μs and an elevated drift tube pressure of 1802 hPa.…”