Microfluidic Electrochemistry Meets Trapped Ion Mobility Spectrometry and High-Resolution Mass Spectrometry—In Situ Generation, Separation, and Detection of Isomeric Conjugates of Paracetamol and Ethoxyquin

Abstract

Over the last 3 decades, electrochemistry (EC) has been successfully applied in phase I and phase II metabolism simulation studies. The electrochemically generated phase I metabolite-like oxidation products can react with selected reagents to form phase II conjugates. During conjugate formation, the generation of isomeric compounds is possible. Such isomeric conjugates are often separated by high-performance liquid chromatography (HPLC). Here, we demonstrate a powerful approach that combines EC with ion mobility spectrometry to separate possible isomeric conjugates. In detail, we present the hyphenation of a microfluidic electrochemical chip with an integrated mixer coupled online to trapped ion mobility spectrometry (TIMS) and time-of-flight high-resolution mass spectrometry (ToF-HRMS), briefly chipEC-TIMS-ToF-HRMS. This novel method achieves results in several minutes, which is much faster than traditional separation approaches like HPLC, and was applied to the drug paracetamol and the controversial feed preservative ethoxyquin. The analytes were oxidized in situ in the electrochemical microfluidic chip under formation of reactive intermediates and mixed with different thiol-containing reagents to form conjugates. These were analyzed by TIMS-ToF-HRMS to identify possible isomers. It was observed that the oxidation products of both paracetamol and ethoxyquin form two isomeric conjugates, which are characterized by different ion mobilities, with each reagent. Therefore, using this hyphenated technique, it is possible to not only form reactive oxidation products and their conjugates in situ but also separate and detect these isomeric conjugates within only a few minutes.

Ion Mobility Mass Spectrometry for the Separation and Characterization of Small Molecules

“…The commercial TIMS, produced by Bruker Corp., is connected to the QTOF behind the mobility tube, and by adjusting the ion release device to synchronize with the selection of precursors for ion fragmentation, a unique parallel accumulation-serial fragmentation (PASEF) operating mode is formed, significantly increasing the data acquisition rate. Selected accumulation trapped ion mobility spectrometry (SA-TIMS) and gated TIMS can adjust the scanning rate, which can be coupled with the slower quality analysis process. , The use of chip electrochromatography before IMS detection contributes to the distribution of peaks and the increase of peak capacity. , Connecting the ion cyclotron resonance cell with mobility selection function after TIMS can reduce the screening of isomerism candidate structures . In order to analyze the molecular structure of specific charge state more accurately, a tandem TIMS technology can be adopted .…”

Microfluidic nanodevices for drug sensing and screening applications

“…Therefore, mass spectrometry can be used for the identification or confirmation of molecules ( Domon and Aebersold, 2006 ; Sansa et al, 2020 ). The integration of microfluidics with mass spectrometry provides a simple and sensitive analytical workflow process ( Kazoe et al, 2021 ; Liu and Lin, 2016 ; D. Zhang et al, 2021 ) with automation capability, reduced sample preparation ( Liu and Lin, 2016 ), shorter analysis time ( Korzhenko et al, 2021 ), good reusability, high throughput ( Looby et al, 2019 ), high characterization capability ( Shen et al, 2021 ), and easy integration with various isolated instruments ( Spencer et al, 2022 ), thus greatly enhancing the analytical capability. Herein, the integration of mass spectrometry and microfluidics is ideally suited for highly sensitive drug screening.…”

“…Herein, the integration of mass spectrometry and microfluidics is ideally suited for highly sensitive drug screening. Drug screening covers a wide range of topics, including the retention of antibiotics in food ( Wu et al, 2016 ; Zhao et al, 2019 ), monitoring of blood levels of therapeutic drugs for clinical diagnosis ( Kazoe et al, 2021b ; Korzhenko et al, 2021b ; Spencer et al, 2022b ; Tascon et al, 2018 ), and screening of anticancer drugs ( Lin et al, 2016b ; Sun et al, 2020 ; Wu et al, 2016b ).…”

The Combination of Electrochemistry and Microfluidic Technology in Drug Metabolism Studies

“…Identifying isomeric metabolites is a real challenge in microfluidic electrochemistry, considering their instability and quick degradation. Owe karst team hyphenated online for the first time in electrochemical metabolism an electrochemical chip with ion mobility spectrometry (IMS), [103] an analytical technique capable to separate compounds in 1 s. Traditional methods like HPLC require several minutes to separate the electro‐generated metabolites and this might cause degradation issues. However, separation columns have been added successfully on previous instrumental set‐ups involving conventional flow cells.…”