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Evaporative derivatization of phenols with 2‐sulfobenzoic anhydride for detection by matrix‐assisted laser desorption/ionization mass spectrometry
Author(s) -
Yao Yuanyuan,
Wang Poguang,
Giese Roger
Publication year - 2014
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.6816
Subject(s) - chemistry , derivatization , mass spectrometry , chromatography , direct electron ionization liquid chromatography–mass spectrometry interface , chemical ionization , ionization , organic chemistry , ion
RATIONALE Phenols are an important class of analytes, for example as bioactive environmental contaminants. Towards a goal of improving their detection by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF‐MS) or MALDI‐tandem time‐of‐flight (TOF/TOF)‐MS, we studied their derivatization with 2‐sulfobenzoic anhydride (SBA). We chose SBA for this purpose since it is commercially available, inexpensive, and forms an anionic derivative. METHODS Under the selected conditions developed here for phenols, a reaction mixture of one or more of such compounds in acetonitrile containing SBA and 4‐dimethylaminopyridine (DMAP) is evaporated to a solid, heated at 60 °C for 1 h, redissolved in 50% acetonitrile containing matrix, spotted onto a MALDI target, and subjected to negative ion MALDI‐TOF/TOF‐MS. RESULTS While conventional (solution‐phase) reaction of 4‐phenylphenol (model analyte) with SBA and DMAP only gave a 47% yield of SBA‐tagged 4‐phenylphenol, evaporative derivatization as above gave a 96% yield, and 25 pmol (4.3 ng) of 4‐phenylphenol could be detected in this way by MALDI‐TOF/TOF‐MS at signal‐to‐noise ratio (S/N) = 260, whereas even 1 nmol of the nonderivatized phenol was not detected in the absence of derivatization. A wide range of responses was observed when a mixture of 15 phenols was derivatized, with the higher responses coming from phenols with a p K a value above 9. Without derivatization, phenols with p K a values below 5 were the most readily detected. CONCLUSIONS Evaporative derivatization with SBA (a convenient reagent) can improve the detection of phenols with relatively high p K a values (above 9) by negative ion MALDI‐TOF‐MS, and accomplish this in the absence of post‐derivatization reaction cleanup. Copyright © 2014 John Wiley & Sons, Ltd.