title: Evaporative derivatization of phenols with 2-sulfobenzoic anhydride for detection by matrix-assisted laser desorption/ionization mass spectrometry.
abstract: BACKGROUND
  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 pKa value above 9. Without derivatization, phenols with pKa 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 pKa values (above 9) by negative ion MALDI-TOF-MS, and accomplish this in the absence of post-derivatization reaction cleanup.
authors: Department of Pharmaceutical Sciences and Barnett Institute, Bouve College, Northeastern University, Boston, MA, 02115, USA.
authors: Yuanyuan
authors: Y
authors: Yao
authors: Poguang
authors: P
authors: Wang
authors: Roger
authors: R
authors: Giese
mesh_terms: D015761:4-Aminopyridine / Q000031:analogs & derivatives / Q000737:chemistry; D001565:Benzoates / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D010636:Phenols / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
chemical_list: D001565:Benzoates; D010636:Phenols; C028022:2-sulfobenzoic acid cyclic anhydride; D015761:4-Aminopyridine; C003885:4-dimethylaminopyridine