LC-MS is one of the top analysis instruments. Liquid chromatographs separate organic chemicals in liquid. Mass spectrometers analyze separated chemicals one by one. Information of molecular weight, structure (in some cases) and quantity come out from MS. The powerful API (Atmospheric Pressure Ionization) techniques including ESI (Electrospray Ionization) and APCI (Atmospheric Pressure Chemical Ionization) make spectra simple and easy to analyze. LC-MS is widely used in food industry, pharmaceutical industry, cosmetic industry, forensics, research institutes, universities and so on.