1. Ambient mass spectrometry using Desorption Electrospray Ionization (DESI) Farzad Fani Pakdel Group meeting Thursday March 23, 2006

2. Summary  About DESI  Normal experimental conditions  Some applications  DESI and DART  Advantages

3. Ambient mass spectrometry http://www.jeolusa.com/ms/msprods/accutof_dart.html Robert Cody at Jeol USA, Inc, MA TOF No sample preparation Fast analysis

4. About DESI  Reported in 2004 by R. Graham Cooks, Purdue University, IN  Combination of ESI and DI (SIMS or Laser Desorption)  Charged droplets and ions of solvent are sprayed onto the sample for ionization  Water or water-Methanol spray on a surface  It is a soft ionization technique  Large and small molecules: Amino acids, drugs, alkaloids, terpenoids and steroids, peptides and proteins  on metal, polymer (PTFE) and mineral surfaces

5. INSTRUMENTATION

6. Experimental Condition  Sample is on PTFE (PolytetrafluoroEthylene) surface  1-1 water-methanol was used as spray solvent, 0.1% TFA  Flow rate 3-15  L/min  The High voltage = 4 kV  Nominal velocity of nebulizing gas = 350 m / s

7. Capillary inlet-sample distance 2 mm Tip-sample distance 5 mm Incident angle (α) 50 degrees Collection angle (β) 10 degrees

8. Applications of DESI Large variety of applications like other MS methods Particularly promising for forensic and public safety applications: Detection of Explosives Chemical warfare monitoring Analysis of Blood and Urine Tissue imaging

9. RDX = 222 g / mol CF 3 COOH TFA = 114 g / mol Example: Explosive detection

10. 1ng of RDX on 1 mm 2 of leather Commercial ion trap used Negative mode M-1

11. P O Me OO M w = 124 DMMP chemical warfare agents simulant (simulate or stimulate) DESI of nitrile gloves exposed to DMMP vapor for less than one second and then washed

12. Limit of detection for explosives

13. Skin of a Fruit (tomato!!!)

14. Large non-polar molecules

15. Movement of tip and sample

16. Tissue imaging Certain phospholipids in liver

17. DESI or DART?

18. DESI vs. DART 1-5 KV +- 100 V5-25 mm

19. Advantages of DESI  Ambient condition  Large range of molecules from small to proteins  Sample can be moved in space during analysis (Imaging)  No need for Matrix unlike MALDI  Multiple charge ions is an advantage to extend mass range (proteins)  Variable distance and angel allows different energy levels and makes it proper for a wider range of molecules (Proteins)  Reactant molecules (TFA) can be sprayed to enhance ion complex formation Disadvantage ------- uses solvent!!!!!

20. REFRENCES DESI by Cooks : (26 out of 35) Science. 2006 ; Vol. 311,1566 - 1570 J. Mass Spectrom. 2005; 40: 1261–1275 Anal. Chem. 2005, 77, 6915-6927 Science. 2004; Vol. 306, 471-473 DART: Robert B. Cody, James A. Laramee, and H. Dupont Durst, Anal. Chem. 2005, 77, 2297-2302.