The term ionic liquid refers to organic salts with relatively low melting points (below 100 °C) that usually consist of an organic cation or anion and a counterion, in either organic or inorganic form.
The term ionic liquid refers to organic salts with relatively low melting points (below 100 °C) that usually consist of an organic cation or anion and a counterion, in either organic or inorganic form. Ionic liquids exhibit unique characteristics such as extremely low vapor pressure, excellent thermal stability, electrical conductivity, a high degree of polarity, and miscibility with various types of solvents. Ionic liquids have been used as catalysts and solvents in organic chemistry and electrochemistry, and as mobile phase modifiers or functionalized stationary phases in separation science (1–3).
Analytical methods for ionic liquid characterization are challenging due to the complexity of the cationic or anionic organic ions, counterions, and ionic impurities. Ion chromatography (IC), liquid chromatography (LC), and hydrophilic interaction chromatography (HILIC) have been used for ionic liquid analysis, featuring ion-exchange or reversed-phase columns (4–6).
This study describes the first LC–MS method for the simultaneous analysis of ionic liquids, counterions, and halide impurities in a single chromatographic run on an Acclaim® Trinity™ P1 trimode column, using mass spectrometry to ensure selective and sensitive detection.
The experiment was performed on an LC–MS system consisting of an UltiMate® 3000 HPLC system coupled to a MSQ Plus™ single quadrupole mass spectrometer with electrospray ionization interface. Chromatographic separation was achieved on an Acclaim Trinity P1 column (2.1 × 100 mm, 3 μm) with a gradient elution: A: acetonitrile; B: 100 mM ammonium acetate, pH 5.2; C: DI water. B was kept constant at 5%, A was increased from 55% (2 min) to 60% in 8 min then 90% in 1 min and kept at 90% for 7 min.
MSQ Plus was operated in selected ion monitoring (SIM) mode and probe temperature was set at 500 °C, nitrogen was used as nebulizer gas at 85 psi and needle voltage was set at 1 kV.
As shown in Figure 1, ionic liquids, counterions, and impurities were chromatographically separated on the Acclaim Trinity trimode column. Analytes were eluted in groups in the following order: organic cations, inorganic cations, inorganic anions, and organic anions. The upper traces in Figure 1 show the SIM chromatograms of selected analytes, illustrating the specificity and selectivity of the MSQ Plus detector.
Figure 1
This study demonstrates the unique properties and superior chromatographic performance of the Acclaim Trinity trimode column and its application for simultaneous analysis of ionic liquids, counterions, and impurities. This method can be used for ionic liquid quality assurance, contamination analysis, and residue assessment of any removal process.
(1) Z. Yang and W. Pan, Enzyme and Microbial Tech. 37, 19–28 (2005).
(2) C. B. Marisa, G. E. Russell, and G. C. Richard, Chem. Phys. Chem. 5, 1106–1120 (2004).
(3) J. L. Anderson and D. W. Armstrong, Anal. Chem. 75, 4851–4858 (2003).
(4) A. Stojanovic, et al., J. Chromatogr., A 1209, 179–187 (2008).
(5) G. Le Rouzo, et al., J. Chromatogr., A 1164, 139–144 (2007).
(6) F. Hao, P. R. Haddad, and T. Ruther, Chromatographia 495–498 (2008).
Trinity is a trademark and Acclaim and UltiMate are registered trademarks of Dionex Corporation.
MSQ Plus is a trademark of Thermo Fisher Scientific, Inc.
Dionex Corporation
1228 Titan Way, P.O. Box 3603, Sunnyvale, CA 94088
tel. (408)737-0700; fax (408)730-9403
Website: www.dionex.com
Top-down characterization of engineered Bcl-xL proteoforms
October 11th 2024Top-down fragmentation enables rapid characterization of phosphorylated proteins without extensive sample preparation and digestion. In this study, electron capture dissociation (ECD) was used to fragment proteoforms of the cell death-related protein, Bcl-xL. Using these methods, 85–90% sequence coverage was achieved for Bcl-xL proteoforms, allowing for effective localization of phosphorylation within minutes.
Antibody peptide mapping using the new Agilent ExD cell
October 11th 2024Enhanced antibody analysis using electron capture dissociation (ECD) allows for precise glycan localization in low-abundance glycopeptides. This study compares the fragmentation of trastuzumab tryptic digests using ECD and collision-induced dissociation (CID). While CID generates abundant glycan HexNAc ions at 204 m/z, ECD preserves the labile glycan group, enabling accurate site localization.
Identification of Amino Acid Isomers Using Electron Capture Dissociation
October 11th 2024Electron capture dissociation produces distinct fragments of amino acid side chains, enabling the identification of isomeric amino acids such as leucine and isoleucine. This application note demonstrates the isomer identification workflow for peptides and intact proteins using the new Agilent ExD cell and ExDViewer software for fragment analysis.
Trends, Best Practices, and Analytical Challenges in Chemical Characterization of Medical Devices
October 7th 2024Chemical characterization of medical devices, including drug-device combination products, is crucial for ensuring regulatory compliance and patient safety by identifying and quantifying chemicals that may interact with the human body. This paper explores current trends, best practices, and regulatory developments in extractables and leachables (E&L) testing for medical devices.