Qualitative and Quantitative Analysis of Small Amine Molecules by MALDI-TOF Mass Spectrometry through Charge Derivatization

摘要

A pair of isotopically coded light and heavy reagents,tris-(2,4,6-trimethoxyphenyI)phosphonium acetic acid N-hy-droxysuccinimide esters (1 and 2) were synthesized and used to derivatize low molecular weight (<500 Da) molecules containing primary or secondary amine functional groups for MALDI-TOF MS analysis.The light and heavy reagents added a 573 and 600 Da positively charged tag to each analyte,respectively.In die presence of 10 times excess of tag reagents,the coupling reactions reached near completion within 10 min.The derivatiza-tion greatly facilitated MALDI analysis of small molecules and significantly improved the sensitivity of analysis,allowing a limit of detection in the low femtomole range.Additionally,the reaction mixtures were directly analyzed by MALDI without sample cleanup.The quantification of small molecules by MALDI-TOF MS was successfully achieved by analysis of isotopically coded light and heavy derivatives.MALDI-TOF quantitative analysis of a mixture of antibiotics yielded calibration curves in the concentration range from 0.3 to 30 pmol/muL with r~2 values greater than 0.9995.