**1.2. The principle of mass spectrometry**

Mass spectrometry (MS) is an analytical technique based on the principle of gas phase ion chemistry which allows the identification of analytes of any molecular weight and in any physical state. The availability of (i) multifaceted sample preparation, (ii) high throughput methods for on-line multistep mixture separation, (iii) multistep (MS/MS) ion analysis, (iv) high resolution acquisition and (v) specific isotopic analysis, confer to MS the unique feature of a methodology that can be directly applied to complex natural mixtures such as olive oil.
