Page 223 - Multidimensional Chromatography

Multidimensional Chromatography
Edited by Luigi Mondello, Alastair C. Lewis and Keith D. Bartle
Copyright © 2002 John Wiley & Sons Ltd
ISBNs: 0-471-98869-3 (Hardback); 0-470-84577-5 (Electronic)

10 Multidimensional Chromatography:
Foods, Flavours and Fragrances

Applications

G. DUGO, P. DUGO and L. MONDELLO
Università di Messina, Messina, Italy

10.1 INTRODUCTION
Chromatography is the best technique for the separation of complex mixtures.
Frequently, samples to be analysed are very complex, so the analyst has to choose
more and more sophisticated techniques. Multidimensional separations, off-line and
recently on-line, have been used for the analysis of such complex samples.
Food, flavour and fragrance products are a good example of natural complex mix-
tures. The analysis of these matrices may be carried out to:
• determine the qualitative and/or quantitative composition of a specific class of
components;
• control the quality and the authenticity of the product;
• detect the presence of adulteration or contamination.
Sometimes, the monodimensional separation cannot be sufficient to resolve all of
the components of interest. Problems of peak overlapping may occur, and a pre-
separation of the sample is often necessary. This pre-separation has the aim of reduc-
ing the complexity of the original sample matrix, by separating a simpler fraction
than the original matrix. The fraction should contain the same amount of the analyte
as in the whole sample, ready for analysis and free from substances that can interfere
during the chromatographic analysis. Often, the preseparation is carried out off-line
because it is easy to operate, although it can present many disadvantages, such as
long separation times, the possibility of contamination or formation of artefacts, the
difficulty of a quantitative recovery of the components of interest, etc. On the other
hand, many on-line pre-separation methods have now been developed that have the
advantages of greatly reducing the total analysis time, compared to classical off-line
sample preparation techniques, to give a good recovery of the analytes with minimal
chance for contamination. The disadvantage is that the equipment is significantly
more complex and expensive than for monodimensional chromatography.