a typical apci usually consists of three main parts: a nebulizer probe which can be heated to 350-500c, an ionization region with a corona discharge needle, and an ion-transfer region under intermediate pressure. the analyte in solution is introduced from a direct inlet probe or a liquid chromatography (lc) eluate into a pneumatic nebulizer with a flow rate 0.2–2.0ml/min. in the heated nebulizer, the analyte coaxially flows with nebulizer n gas to produce a mist of fine droplets. by the combination effects of heat and gas flow, the emerged mist is converted into a gas stream. once the gas stream arrives in the ionization region under atmospheric pressure, molecules are ionized at corona discharge which is 2 to 3 kv potential different to the exit counter-electrode. sample ions then pass through a small orifice skimmer into the ion-transfer region. ions may be transported through additional skimmer or ion-focusing lenses into a mass analyzer for subsequent mass analysis.