UPLC and monolithic HPLC/ESI-MS and MS/MS determination of carnitine and acylcarnitines

SOLEDAD CERUTTI; TIMOTHY GARRET; PEGGY R. BORUM; JODIE V. JOHNSON; RICHARD A. YOST; DAVID H. POWELL

Indianapolis, Indiana, Estados Unidos

Conferencia; 55th ASMS Conference on Mass Spectrometry and Allied Topics; 2007

American Society for Mass Spectrometry

Due to the zwitterionic nature of acylcarnitines, acidic conditions were used to promote protonation of the carboxylic group, which resulted in the production of positively charged quaternary amines. Thus, the positive ESI normal mass spectra of acylcarnitines were dominated by their [M+H]+ ions with minimal fragmentation. Collision-induced dissociation (CID) of the acylcarnitines’ [M+H]+ ions was accomplished via the conventional mass-selected method on the triple quadrupole and via the non-mass-selected in-source CID on the oa-TOF-MS. The effects of CID energy were investigated with each instrument. The acylcarnitines’ [M+H]+ ions underwent CID on both instruments to produce similar product ions. The major product ions were m/z 60, [(CH3)3NH]+, and m/z 85, [CH2CHCHCOOH]+ and product ions resulting from a common neutral loss of (CH3)3N (59 u) and from the loss of the carnitine backbone (161 u). The TQ MS/MS technique yielded the more informative fragmentation patterns, especially for the least abundant product ions. Useful fragmentation fingerprints were also obtained with source collision-induced dissociation on the oa-TOF but with the higher m/z resolution and accuracy. Compared to the 1.8 μm particle size C18 HPLC column, higher chromatographic resolution was obtained with the very small particle silica-based monolithic column. The gradient time was greatly reduced. The chromatographic profile of eluting acylcarnitines was dramatically improved using this rapid gradient. Rapid, comprehensive, and high-resolution acylcarnitine separation for metabolomics was achieved. The methodology will be discussed and the results of these analyses will be presented, together with the results of our ongoing studies for profiling acylcarnitines in clinical samples.