VOLATILE COMPOSITION OF WINES USING A GC/TOFMS: HS-SPME VS MICRO LLE AS SAMPLE PREPARATION METHODOLOGY

Abstract

Wine aroma analysis can be done by sensorial or instrumental analysis, the latter involving several methodologies based on olfactometric detection, electronic noses or gas chromatography. Gas Chromato-graphy has been widely used for the study of the volatile composition of wines and depending on the detection system coupled to the chromatographic system, quantification and identification of individual compounds can be achieved.

Prior to the chromatography, a sample preparation step is almost always required, but unfortunately there is no extraction procedure that can aid in the detection of the wide range of volatile compounds that exists in a wine sample. Wine volatile profile is characterized to have thousands of compounds with varying chemical properties, like molecular weight, structure, polarity and molecular structures. Moreover, they exist in a wide range of concentration, which, sometimes implies that a pre-concentration step is also required, if the ones existing in very low concentrations are of interest. As far as sample preparation methods for the analysis of wine aroma concerns, one can found thousands of bibliographic references, but the most used ones are probably the liquid-liquid extraction (LLE) and the solid-phase microextraction (SPME). Extensive reviews on the different sample preparation methods that has been used for wine analysis, along with each one advantages and drawbacks, has already received researcher’s attention (Costa Freitas et al, 2012)

In light of the above, this work intents to discuss the use of two different sample preparation methods to quantify and identify volatile compounds in wines.

Two sample preparation methods were compared: a micro liquid-liquid extraction with 500mL of dichloromethane (based on Vilanova et al, 2010) and a HS-SPME (based on Pereira et al 2021). Chromatographic method was the same for both sample preparation method.

The number of compounds identified by HS-SPME was higher than the ones identified by micro-LLE. 26 compounds were identified in wines by both sample preparation methods. Since the majority of com-pounds identified by each sample preparation methodologies are different, choose to do one or another, or even both, should be taken into consideration when the goal is to go deep on volatile composition of wines.