Multiple automated headspace in-tube extraction for the accurate analysis of relevant wine aroma compounds and for the estimation of their relative liquid–gas transfer rates

Release and Formation of Oxidation-Related Aldehydes during Wine Oxidation

“…This possibility has been recently suggested when the aldehyde formation rates of wines exposed to different levels of oxygen were found to be strongly correlated to the wine levels in combined SO 2 . 6 Previous observations about the strong differences in volatility of wine aldehydes 17 would be also consistent with the relevance of their bound forms. The documented existence of those adducts 18,19 and the likely reversibility of the equilibrium, makes that, without the ability to discern free from bound forms, it is not possible to make a correct diagnose about the nature of the problem.…”

Simultaneous determination of free and bonded forms of odor-active carbonyls in wine using a headspace solid phase microextraction strategy

“…Free forms of long chain aliphatic aldehydes in normal wines (octanal, nonanal and decanal) were found to range from as low as 4% to up to 76% of the total content [12], and a significant part of the complexes (up to 89%) could not be recovered by incubation with acetaldehyde, but with heptanal, suggesting the existence of hydrophobic complexes, maybe with proteins [13]. Most recently, the apparent liquid-gas distribution coefficients of acetaldehyde and 2,3-pentanedione were found to differ by factors up to 17 or 11 between wines, respectively [14], far more than any other volatile studied, supporting a relevant role of carbonyl-matrix interactions on wine sensory properties. Moreover, carbonyl production rates upon wine oxidation have been found to be related to the wine content in combined SO 2 , suggesting that a significant part of the aldehydes could be already present in wine under the form of SO 2 adducts [15].…”

“…These approaches, however, require the previous knowledge of the total concentration of the analyte and need to be complemented by a second method and may have sensitivity problems. There are some more sophisticated alternatives that can provide a simultaneous estimation of the gas-liquid distribution coefficient and of the total amount, such as the phase ratio [31], multiple headspace extractions [32] or multiple headspace in tube extraction [14]. In all these cases, several determinations are also required and sensitivity and selectivity can be also of concern.…”

Optimization strategies of in-tube extraction (ITEX) methods

“…While the extraction flow through the trap and the number of performed extraction strokes are the defining factors for the extracted amount and necessary extraction time in analytical applications, they are mostly optimized to the maximum extraction yield, individually [ 3 , 18 ]. Although most authors used a method with a high extraction flow and a large number of extraction strokes [ 3 , 19 , 20 , 18 , 15 ], the measurement of different combinations of extraction strokes and flows has so far only been reported, recently [ 21 , 4 ]. Therefore, after discussing both individual parameters, special emphasis will be laid on the interaction of both parameters to achieve an optimum extraction yield in a predefined extraction time, for instance in parallel to the GC oven runtime.…”