1. Atmospheric Pressure Ionization - Time of flight mass spectrometry (API-TOF/MS) API-TOF/MS is the integration of two instrumental techniques, API and TOF/MS. Both are relatively simple and are based on fundamental ideas about charged particles. But fundamentals first: What is API What is TOF/MS Integration of API and TOF/MS into one Why API-TOF/MS

2. API Chemical ionization in the air at atmospheric pressure.  -rays produced by tungsten wire. Inelastic collisions between carrier gas Ionization of He carrier gas –He + + A ==> He + A +

3. TOF/MS Analyte is usually ionized by a focused laser. Vaporized and ionized particles are forced down a drift tube by means of an applied potential to the tube. Separation occurs due to differing m/z. Lightest ones first, heaviest last (1 to 30  s). Ion transducer is in essence a PMT. Internal TOF/MS pressure is between 10 -5 to 10 -8 torr.

4. Integration of API to TOF/MS Two main hurdles: –Differing pressures between API and TOF/MS –TOF/MS requires a pulse for time determination. Pressure gradient: –Differentially pumped interfaces. Pulse production: “ion packet” –Plate Deflector method

5. Why API-TOF/MS Increased resolution Low detection capabilities, 100 femtomolar range. –Multi-hit method. –Single-hit method. API promotes “soft ionization” Non-volatile substances can be ionized more easily Full mass spectrum can be taken on every injection. High mass compounds can be determined. Easy to use and relatively inexpensive.