title: Desorption atmospheric pressure photoionization and direct analysis in real time coupled with travelling wave ion mobility mass spectrometry.
abstract: BACKGROUND
  Ambient mass spectrometry (MS) is a tool for screening analytes directly from sample surfaces. However, background impurities may complicate the spectra and therefore fast separation techniques are needed. Here, we demonstrate the use of travelling wave ion mobility spectrometry in a comparative study of two ambient MS techniques.
  
  
  METHODS
  Desorption atmospheric pressure photoionization (DAPPI) and direct analysis in real time (DART) were coupled with travelling wave ion mobility mass spectrometry (TWIM-MS) for highly selective surface analysis. The ionization efficiencies of DAPPI and DART were compared. Test compounds were: bisphenol A, benzo[a]pyrene, ranitidine, cortisol and α-tocopherol. DAPPI-MS and DART-TWIM-MS were also applied to the analysis of chloroquine from dried blood spots, and α-tocopherol from almond surface, and DAPPI-TWIM-MS was applied to analysis of pharmaceuticals and multivitamin tablets.
  
  
  RESULTS
  DAPPI was approximately 100 times more sensitive than DART for bisphenol A and 10-20 times more sensitive for the other compounds. The limits of detection were between 30-290 and 330-8200 fmol for DAPPI and DART, respectively. Also, from the authentic samples, DAPPI ionized chloroquine and α-tocopherol more efficiently than DART. The mobility separation enabled the detection of species with low signal intensities, e.g. thiamine and cholecalciferol, in the DAPPI-TWIM-MS analysis of multivitamin tablets.
  
  
  CONCLUSIONS
  DAPPI ionized the studied compounds of interest more efficiently than DART. For both DAPPI and DART, the mobility separation prior to MS analysis reduced the amount of chemical noise in the mass spectrum and significantly increased the signal-to-noise ratio for the analytes.
authors.affiliation: Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, P.O. Box 56, 00014, Helsinki, Finland; School of Chemistry and Biochemistry, Georgia Institute of Technology, 901 Atlantic Drive NW, Atlanta, GA, 30332, USA.
authors.forename: Riikka-Marjaana
authors.initials: RM
authors.lastname: Räsänen
authors.forename: Prabha
authors.initials: P
authors.lastname: Dwivedi
authors.forename: Facundo M
authors.initials: FM
authors.lastname: Fernández
authors.forename: Tiina J
authors.initials: TJ
authors.lastname: Kauppila
mesh_terms: D001274:Atmospheric Pressure; D059788:Dried Blood Spot Testing; D006801:Humans; D013058:Mass Spectrometry / Q000379:methods*; D009930:Organic Chemicals / Q000032:analysis / Q000737:chemistry; D055668:Photochemical Processes; D059629:Signal-To-Noise Ratio; D013607:Tablets / Q000737:chemistry
chemical_list: D009930:Organic Chemicals; D013607:Tablets