Application of multiple headspace-solid-phase microextraction followed by gas chromatography-mass spectrometry to quantitative analysis of tomato aroma components.

The objective of this paper is to investigate the potential of multiple headspace-solid-phase microextraction (MHS-SPME) for the determination of volatile compounds in complex matrix samples. A method based on MHS-SPME for the determination of around 20 volatile compounds, responsible of tomato flavour and aroma has been developed and validated, using gas chromatography with mass spectrometry (ion trap analyser) for analysis. For this purpose, the experimental beta parameter, resulting from the MHS-SPME theoretical development, has been obtained from real sample analysis (in triplicate) for each identified compound, carrying out up to 5 consecutive extractions. Later, this parameter is used to perform quantitation of real samples after just a single HS-SPME extraction. Precision, expressed as repeatability, has been evaluated by analysing six replicates of a real sample, showing relative standard deviations between 4 and 20%. For accuracy study, quantitative results have been compared with those obtained by means of standard additions on replicate samples, and no statistically significant differences between the two methods were observed. Since MHS-SPME uses the estimated total area corresponding to the complete extraction of compounds (obtained from the beta parameter), quantitation can be carried out by external calibration using standards in solvent and splitless injection, instead of by SPME. Linearity, tested in the range 0.05-15 microg/mL, showed satisfactory values, with coefficients of correlation between 0.995 and 0.999. Limits of detection were in the range of 0.25-5 ng/g. MHS-SPME has been proved to be an adequate technique to avoid matrix effects in complex samples quantitation. Its applicability to the determination of volatile tomato components, together with its limitations, is discussed in this article.