RATIONALE
Electrospray mass spectrometry (ESI-MS) is one of the most popular techniques for obtaining structural information, which is commonly used in bioanalysis and clinical diagnostics. However, for the detection of complicated samples with high reactivities (such as reactive sulfur species, RSS), traditional ESI-MS usually suffers from overlapped and inaccurate signals. Herein, based on the multiphase flow of extractive electrospray ionization (MF-EESI), an ambient MS technique of online derivatization was proposed to detect thiols without any other sample pretreatment.
METHODS
RSS molecules and the derivatization reagent of 4-Chloro-7-nitro-1,2,3-benzoxadiazole (NBD-Cl) were introduced into the internal and innermost capillary of the MF-EESI system, respectively. By a high-velocity nebulizing stream of N2 gas through an external capillary, both flows of innermost biothiols and internal NBD-Cl were electrosprayed and mixed for online reactions. Therefore, the fast derivatization of thiols was employed to generate stable ionized derivatives for MS detection.
RESULTS
By evaluating the changes of MS signals before and after the derivatization, the ions of RSS were identified simply and correctly. Without any sample pretreatment, the fast detection of cysteine, homocysteine, and glutathione has been achieved in the complicated samples.
CONCLUSIONS
The present online derivatization-based MF-EESI was successfully used for fast, simple, and accurate detection of biothiols. This presented a potential pathway for the fast identification of thiols in complicated samples.