MALDI matrix cluster ions as internal references for ion mobility measurements

UNCG Author/Contributor (non-UNCG co-authors, if there are any, appear on document)
Norman H. Chiu, Assistant Professor (Creator)
Daniel A. Todd (Creator)
The University of North Carolina at Greensboro (UNCG )
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Abstract: In the absence of high vacuum, the mobility of ions in an electric field is dependent on the charge, mass, shape and size of the ions. To achieve accurate calibration for ion mobility measurements, it is important to select calibrants with comparable physical properties to the molecular ions of interest. The size of an ion is often referred as its collision cross section (CCS). Currently, the information on the CCS values of various types of molecular ions are limited, thus representing a challenge to the calibration of ion mobility spectrometry. In this study, instead of finding a way to improve the calibration of ion mobility measurements, the intrinsic by-products of the conventional matrix-assisted laser desorption/ionization (MALDI) technique, namely MALDI matrix cluster (MAC) ions, are being used as internal references for ion mobility measurements. The standard MALDI matrix and sample preparation method are used. During the MALDI ionization process, MAC ions are generated and co-exist with the molecular ions of interest within the ion source. Our results indicate the MAC ions do possess suitable ion mobility characteristics, thus allowing the MAC ions to serve as internal reference for ion mobility measurements. The MAC ions cannot be used as internal standard or calibrants for ion mobility measurements, because their molecular structures as well as their CCS are unknown. However, the detection of MAC ions can allow us to determine whether the normal operation as well as the expected performance on the sensitivity and resolution of ion mobility spectrometry are achievable and reproducible. The MAC ions can also facilitate the transfer of specific experimental protocols between ion mobility instruments and/or laboratories. No extra materials, equipment or procedure are required for using MAC ions. For the proof of concept, all experimental work in this study was carried out on a traveling wave ion mobility mass spectrometry platform.

Additional Information

International Journal for Ion Mobility Spectrometry
Language: English
Date: 2019
Ion mobility, MALDI, Matrix, Internal reference

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