Matrix-Assisted Ionization-Ion Mobility Spectrometry-Mass Spectrometry: Selective Analysis of a Europium–PEG Complex in a Crude Mixture

• Published in: Journal of the American Society for Mass Spectrometry 2015-12, Vol.26 (12), p.2086-2095
• Main Authors: Fischer, Joshua L., Lutomski, Corinne A., El-Baba, Tarick J., Siriwardena-Mahanama, Buddhima N., Weidner, Steffen M., Falkenhagen, Jana, Allen, Matthew J., Trimpin, Sarah
• Format: Article
• Language: English
• Subjects: Abundance; Analytical Chemistry; Bioinformatics; Biotechnology; Chemistry; Chemistry and Materials Science; Chromatography; Chromatography, Liquid - methods; Coordination Complexes - analysis; Desorption; Equipment Design; Europium; Europium - analysis; Inductively coupled plasma; Ionic mobility; Ionization; Ions; Lasers; Mass spectrometry; Nitriles - chemistry; Organic Chemistry; Phase separation; Polyethylene glycol; Polyethylene Glycols - analysis; Proteomics; Research Article; Scientific imaging; Spectrometry, Mass, Electrospray Ionization - methods; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization - instrumentation; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization - methods; Spectroscopy
• ISSN: 1044-0305; 1879-1123
• DOI: 10.1007/s13361-015-1233-8

The analytical utility of a new and simple to use ionization method, matrix-assisted ionization (MAI), coupled with ion mobility spectrometry (IMS) and mass spectrometry (MS) is used to characterize a 2-armed europium(III)-containing poly(ethylene glycol) (Eu-PEG) complex directly from a crude sample. MAI was used with the matrix 1,2-dicyanobenzene, which affords low chemical background relative to matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI). MAI provides high ion abundance of desired products in comparison to ESI and MALDI. Inductively coupled plasma-MS measurements were used to estimate a maximum of 10% of the crude sample by mass was the 2-arm Eu-PEG complex, supporting evidence of selective ionization of Eu-PEG complexes using the new MAI matrix, 1,2-dicyanobenzene. Multiply charged ions formed in MAI enhance the IMS gas-phase separation, especially relative to the singly charged ions observed with MALDI. Individual components are cleanly separated and readily identified, allowing characterization of the 2-arm Eu-PEG conjugate from a mixture of the 1-arm Eu-PEG complex and unreacted starting materials. Size-exclusion chromatography, liquid chromatography at critical conditions, MALDI-MS, ESI-MS, and ESI-IMS-MS had difficulties with this analysis, or failed. Graphical Abstract ᅟ