*2.7.2 Direct infusion analysis in MS*

Sample direct infusion into the mass spectrometer was one of the first techniques employed in TAG analysis [88]. Its main advantage is the rapidity. However, despite the progresses in the last 15 years, there are three main problems associated with the technique: (1) ion suppression, (2) isotopic interference and (3) differentiation of isomers. Consequently, a chromatographic separation is crucial to avoid ions suppression and to differentiate the isomeric species, being the direct infusion technique rarely employed for characterize lipid in milk sample.
