Application of ICRMS

Virgin olive oil is obtained from the olive, the fruit of the olive tree, using solely mechanical extraction methods in conditions, particularly thermal conditions, which do not alter the oil in any way. It has not to undergo any treatment other than washing, decanting, centrifuging and filtering. It excludes oils obtained by the use of solvents or re-esterification methods, and mixing with oils from other sources. Virgin olive oil has a free acidity, expressed as oleic acid, of not more than 0.8g/100g of oil (0.8%), and the other characteristics of which correspond to those fixed for this category. Virgin olive oils are classified depending on their organoleptic (taste and aroma) and analytical characteristics (the degree of acidity refers to the proportion of free fatty acids, not to the taste). It can be qualified as a natural product, and virgin olive oil can have a designation of origin when it meets the specific characteristics associated with a particular region. Most current methods for detecting oil composition and classification are based on chromatographic analysis. Traditionally, for the determination of fatty acid composition is used the gas-liquid chromatography (GLC) , for triglycerides’ composition is used the high-performance liquid chromatography (HPLC). Chromatographic methods are currently widely used for the qualitative and quantitative analysis of sterols, which comprise a major portion of the unsaponifiable matter. GC-electronic impact ionisation mass spectrometry and on-line LC-GC-flame ionisation is used to detect different sterols in vegetable oils. HPLC coupled with UV detection can analyse tocopherols after saponification; GC-isotope ratio MS can reportedly identify volatile compounds in vegetable oils. The above-listed techniques typically require complicated and time-consuming isolation procedures. For example, GLC analysis requires that fatty acids first be converted to methyl esters; techniques based on quantitative analysis of particular chemical fractions require prior chromatographic separation to isolate triglycerides, sterols, tocopherols, etc. Actually it is possible to characterize the olive oil using the FT ICR MS (Fourier Transform Ion Cyclotron Resonance Mass Spectrometer). This technique combines electro spray ionisation (ESI), a low-fragmentation ionisation technique for polar compounds, with Fourier transform ion cyclotron resonance mass spectrometry, a mass spectrometric technique with ultra-high resolution and mass accuracy capabilities. Applications are surveyed in fields such as proteomics, metabolomics, natural product analysis and non-covalent complexes. This paper focuses on the application of this technique to the direct characterisation of tocopherols and other components in olive oil. The extra virgin oil (Circiriello variety), typical of Apulia region and extracted by decanter on stoned paste, was used for the experimentation. Analysis was performed using a TermoElecton LTQ FT ICR 7 tesla mass spectrometer.