The most common protocols for the quantitative determination of the enantiomeric excess (ee) of raw mixtures by ESI-MS reveal inadequate in cases where the distribution of diastereomeric derivatives diverges from the ee of original solutions. This phenomenon is attributable to a matrix effect, i.e., to the stereospecific formation of high order noncovalent adducts in the ESI droplets, which alters the actual availability of the diastereomeric species under MS analysis. In this frame, the assumption of classic protocols that the ionization correction factor q is independent on the composition of the mixture submitted to analysis is questionable. An alternative methodology is presented in this paper, which is aimed at circumventing the problem by excluding any chemical derivatization of the original raw mixture. It is based on the measurement of the actual distribution of ESI-formed proton-bound diastereomeric complexes from the enantiomeric mixture through a careful analysis of their reaction kinetics with a suitable reactant.

Unexpected behavior of diastereomeric ions in the gas phase: a stimulus for pondering on ee Measurements by ESI-MS / Fraschetti, Caterina; Filippi, Antonello; Crestoni, Maria Elisa; T., Ema; Speranza, Maurizio. - In: JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY. - ISSN 1044-0305. - ELETTRONICO. - 24:4(2013), pp. 573-578. [10.1007/s13361-012-0575-8]

Unexpected behavior of diastereomeric ions in the gas phase: a stimulus for pondering on ee Measurements by ESI-MS

FRASCHETTI, CATERINA;FILIPPI, Antonello;CRESTONI, Maria Elisa;SPERANZA, Maurizio
2013

Abstract

The most common protocols for the quantitative determination of the enantiomeric excess (ee) of raw mixtures by ESI-MS reveal inadequate in cases where the distribution of diastereomeric derivatives diverges from the ee of original solutions. This phenomenon is attributable to a matrix effect, i.e., to the stereospecific formation of high order noncovalent adducts in the ESI droplets, which alters the actual availability of the diastereomeric species under MS analysis. In this frame, the assumption of classic protocols that the ionization correction factor q is independent on the composition of the mixture submitted to analysis is questionable. An alternative methodology is presented in this paper, which is aimed at circumventing the problem by excluding any chemical derivatization of the original raw mixture. It is based on the measurement of the actual distribution of ESI-formed proton-bound diastereomeric complexes from the enantiomeric mixture through a careful analysis of their reaction kinetics with a suitable reactant.
2013
diastereomeric complexes; enantiomeric excess; gas phase
01 Pubblicazione su rivista::01a Articolo in rivista
Unexpected behavior of diastereomeric ions in the gas phase: a stimulus for pondering on ee Measurements by ESI-MS / Fraschetti, Caterina; Filippi, Antonello; Crestoni, Maria Elisa; T., Ema; Speranza, Maurizio. - In: JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY. - ISSN 1044-0305. - ELETTRONICO. - 24:4(2013), pp. 573-578. [10.1007/s13361-012-0575-8]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/515870
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