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Determination of D/L‐amino acids by zero needle voltage electrospray ionisation
Author(s) -
Sørensen Morten B.,
Aaslo Per,
Egsgaard Helge,
Lund Torben
Publication year - 2008
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.3384
Subject(s) - chemistry , electrospray ionization , chromatography , electrospray , epimer , aspartic acid , ionization , ion , mass spectrometry , analytical chemistry (journal) , amino acid , stereochemistry , organic chemistry , biochemistry
Ion formation may be made more efficient than in normal electrospray ionization (ESI) for certain classes of compounds, such as the polar amino acids Glu, Asn, His, Ser, Asp, Arg, Tyr and Lys, by adjusting the voltage of a normal ESI interface needle to zero voltage. For aspartic acid (Asp) the gain in signal‐to‐noise (S/N) ratio of the liquid chromatography/mass spectrometry (LC/MS) chromatograms obtained in the selective ion monitoring (SIM) mode ( m/z 134) with zero needle potential was 40–50 times higher than detection at 4 kV. Ion formation at zero potential is likely to follow a mechanism related to sonic spray ionization. The utility of the zero needle voltage ESI was illustrated by determining the age of a human tooth by the aspartic acid epimerization method. The procedure involved separating the D‐ and L‐aspartic acid of a tooth extract on a chiral HPLC column and detection by zero voltage ESI‐MS 3 . Copyright © 2008 John Wiley & Sons, Ltd.