Mass spectrometry signal enhancement by reductive amination

• Published in: International journal of mass spectrometry Vol. 387; pp. 16 - 23
• Main Authors: Liu, Meng-Chieh, Lin, Yi-Reng, Huang, Mei-Fang, Tsai, De-Cheng, Liang, Shih-Shin
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.08.2015
• Subjects: Mass spectrometry; Multiple reaction monitoring (MRM); Reductive amination; Signal enhancement; Reductive amination; Signal enhancement; Multiple reaction monitoring (MRM); Mass spectrometry
• ISSN: 1387-3806; 1873-2798
• DOI: 10.1016/j.ijms.2015.06.010

•We enhance signal intensities of four organosulfur compounds (OSCs) in MS.•The factor of signal enhancement is a formaldehyde modification.•We demonstrate infusion, SIM and MRM to compare different compounds.•Signal intensities of four OSCs increase from 146.4 to 2494.8 folds by MRM. Organosulfur compounds (OSCs) subjected to reductive amination in the presence of formaldehyde exhibited increased mass spectrometry signal intensities. In this study, four OSCs including S-allyl cysteine, S-allylcysteinine sulfoxide, S-methylcysteine and S-ethylcysteine were generated using isotopic formaldehyde, and mass spectrometry signal intensities of modified and unmodified OSCs were compared. This comparison involved tandem mass spectrometry infusion and detection techniques, such as selected ion monitoring (SIM) and multiple reaction monitoring (MRM). The signal intensities of modified OSCs increased from 2.6 to 39.2 fold by infusion, from 50.0 to 479.6 fold by SIM, and from 146.4 to 2494.8 fold by MRM. Compounds bearing primary amine groups reacted with formaldehyde in high yield and underwent reductive amination in the presence of sodium cyanoborohydride to form a dimethyl group on these amine groups. The modified OSCs showed enhanced intensities because the electron donating dimethyl groups increase their basicity. This signal enhancement is expected to improve the limit of detection in absolute quantification and structural characterization. Therefore, reductive amination involving primary amine groups may find application in the enhancement of mass spectrometry signal intensities.