TY - JOUR
T1 - Unexpected behavior of diastereomeric ions in the GasPhase
T2 - A stimulus for pondering on ee measurements by ESI-MS
AU - Fraschetti, Caterina
AU - Filippi, Antonello
AU - Crestoni, Maria Elisa
AU - Ema, Tadashi
AU - Speranza, Maurizio
PY - 2013/4/1
Y1 - 2013/4/1
N2 - 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. [Figure not available: see fulltext.]
AB - 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. [Figure not available: see fulltext.]
KW - ESI-FT-ICR mass spectrometry
KW - Enantiomeric excess
KW - Gas-phase kinetics
KW - High-throughput parallel screening
KW - Noncovalent complexes
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U2 - 10.1007/s13361-012-0575-8
DO - 10.1007/s13361-012-0575-8
M3 - Article
C2 - 23494298
AN - SCOPUS:84879531701
SN - 1044-0305
VL - 24
SP - 573
EP - 578
JO - Journal of the American Society for Mass Spectrometry
JF - Journal of the American Society for Mass Spectrometry
IS - 4
ER -