Atmospheric Pressure Chemical Ionization

Atmospheric Pressure Chemical Ionization
This is an ionization method in which the sample is ionized using an ion – molecule reaction with a reactant ion.

1. Atmospheric Pressure Chemical Ionization (APCI). PRESENTED BY : VISHAL THAKUR M.PHARM SEM.I Dr. L.H.Hiranandani College Of pharmacy , Ulhasnagar.Maharashtra

2. INTRODUCTION This is an ionization method in which the sample is ionized using an ion – molecule reaction with a reactant ion. Sample solution is nebulized by the N2 nebulizer gas to form a spray as it enters the heater(at about 400°C),and both sample and solvent molecules are vaporized to a gaseous state. The solvent molecules are ionized by the corona discharge, and stable reactant ions are formed.

3. Protein transfer occurs between these reactant ions and sample molecules (ion – molecule reaction), and the sample molecules either add or lose protons to become ions. This ion – molecule reaction is known to occur in a variety of patterns, such as protein shift reactions, electrophilic addition reactions, etc.

4. APCI Diagram

5. The APCI process : The sample is in a flowing stream of a carrier liquid (or gas) and is nebulized at moderate temperatures. This stream is flowed past an ionizer which ionizes the carrier gas/liquid. The ionized stream acts as the primary reactant ions, forming secondary ions with the analytes .

6. The ions are formed at AP in this process, and are sent into the vaccuum In the vaccuum, a free-jet expansion occurs to form a Mach disk and strong adiabatic cooling occurs. Cooling promotes the stability of analyte ions

7. Benefits : Excellent LC/MS interface Good for less-polar compounds Compatible with MS/MS methods Mass range : Low-moderate Typically less than 2000 D.

8. Limitations : Very sensitive to contaminants such as alkali metals or basic compounds . Relatively low ion currents. Relatively complex hardware compared to other ion sources.

9. REFERENCE 1.Http:// Imaisd.Usc.Es / Riaidt / Masas / Imagenes /Apci1.Jpg 2. Hoffman, Edmond, and Vincent Stroobant . Mass Spectrometry: Principles and Applications. Great Britain: John Wiley & Sons Ltd., 2007 3.http:// www.spectroscopynow.com /Spy/ basehtml / SpyH /1,1181,4-0-0-0-0-home-0-0,00.html

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