Analytical Chemistry Publication: Characterization of Vocus for Quantification of TCA in Cork Stoppers

Thermal Desorption – Vocus Enables On-Line Non-Destructive Quantification of 2,4,6-trichloroanisole in Cork Stoppers Below the Perception Threshold

Luca Cappellin, Felipe D. Lopez-Hilfiker, Veronika Pospisilova, Luigi Ciotti, Paolo Pastore, Marc Gonin, and Manuel Hutterli
Analytical Chemistry, 2020
DOI: 10.1021/acs.analchem.0c01326

This publication in Analytical Chemistry demonstrates use of the Vocus mass spectrometer for online, non-destructive quantification of 2,4,6-trichloroanisole (TCA) in cork stoppers below the perception threshold at unprecedented speeds. The Vocus Cork Analyzer couples this analytical performance to an industrial scale autosampler for high-throughput screening and sorting all cork stoppers in manufacturing facilities, with the aim of eliminating cork taint in wine.

Nearly 40 years after Swiss and Italian researchers identified TCA as the compound responsible for cork taint in wine, a  Swiss – Italian research team, formed by TOFWERK, University of Padova and Edmund Mach Foundation, has developed an innovative solution for the long standing challenge of screening high numbers of cork wine stoppers for TCA.

The human threshold for TCA is extremely low, such that a wine contaminated by as little as 1–2 ng/L TCA can be perceived as tainted.  TCA cannot be completely removed from natural cork without damaging the material’s mechanical and structural properties.   Without the possibility to clean the material, stoppers must be screened to ensure that contaminated stoppers are not used in wine bottles.  Any screening method must be non-destructive, sensitive, ultra-fast, and applicable in an industrial environment as a quality control tool. 

Over the last twenty years, secret or patented industry treatments have tried to eradicate this taint without success, while the most used analytical methods have struggled to measure trace TCA measurements with the required speed and robustness.  Sensory screening reaches some goals, but it is expensive, time consuming and difficult to apply objectively, therefore leading to controversial outcomes.  

This study, which uses our Vocus mass spectrometer, is the first demonstration of on-line detection of TCA based on chemical ionization mass spectrometry.  This method omits the use of chromatography and recovers the separation by a combining soft and selective ionization with high-resolution mass spectrometry.  The technique proved capable of non-destructively quantifying TCA contamination in a single cork stopper in 3 seconds with a limit of quantification below the perception threshold. 

The aim of the study is three-fold. We first show that the Vocus can detect TCA in natural cork stoppers at concentrations below the sensory threshold in 3 seconds. The correlation with releasable TCA determinations according to ISO 20752:201419 and OIV is then investigated. Finally, a real industrial scenario is simulated by determining TCA in 10,100 natural cork stoppers from three different batches in just 8 h and 25 min, corresponding to 3 s per cork stopper. This represents the largest dataset of TCA analysis on cork stoppers within the literature and demonstrates the possibility to apply the technique in an industrial environment. 

The Vocus Cork Analyzer couples the Vocus mass spectrometer to an industrial scale autosampler for high-throughput screening and sorting all cork stoppers in manufacturing facilities, with the aim of eliminating cork taint in wine.
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