XII Iberian Meeting of Electrochemistry XVI Meeting of the ...

XII Iberian Meeting of Electrochemistry & XVI Meeting of the Portuguese Electrochemical Society O B 01
Application of a Membraneless Extraction Module in the
Voltammetric Determination of Sulphites in Wine
Luís M. Gonçalves, Miriam F. Anunciação, Inês M. Valente,
João G. Pacheco, José M. Rodrigues, Aquiles A. Barros
Requimte, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto,
Rua do Campo Alegre, no. 687, 4169-007 Porto, Portugal
luis.goncalves@fc.up.pt
In this work, a new methodology for the voltammetric analysis of sulphites in wine is
proposed [1]. It makes use of a recently developed membraneless extraction module
(MLEM) for the analysis of volatile and semi-volatile compounds [2]. Sulphites are
widely used as preservatives in the food industry for their several roles including the
prevention of undesirable microbial growth and oxidation processes. Among a whole
variety of methodologies proposed for the determination of sulphites in wine, the most
used are based on the classical Monier-Williams procedure and the also ancient Ripper
method. Nevertheless, voltammetric-based methodologies appear to be the most
accurate ones. Square-wave voltammetry (SWV) is very advantageous in the
determination of sulphites since there is a direct detection, i.e. it is the SO 2 molecule that
is instrumentally measured in the electrode [3]. The major drawback when using
voltammetry is the previous analyte extraction step required since wine is such a
complex matrix. The extraction process is based on a MLEM that works with the same
principles of pervaporation however it does not require a membrane, and therefore does
not have the associated problems with its use. The sample is placed inside the module
and the volatile compounds evaporate to the headspace. Inside the module there is a
suspended small reactor, where a small volume of an acceptor solution is placed. After a
period of time, the acceptor solution is collected and analyzed by SWV. The proposed
method was validated by comparison to the reference methodology. It showed
repeatability (RSD lower than 5%) and linearity (between 20 to 200 mg L -1 ) as well as
suitable limit of detection (6 mg L -1 ). Moreover, if needed, these limits can be easily
lowered by increasing the time of extraction, which in this case was less than 5 minutes.
Acknowledgments: LMG (SFRH/BD/36791/2007) and JGP (SFRH/BD/30279/2006) wish to
acknowledge Portuguese Fundação para a Ciência e Tecnologia (F CT) for their PhD studentships.
References
[1] Gonçalves, L.M.; Anunciação, M.F., Valente, I.M., Pacheco, J.G.; Magalhães, P.J.; Rodrigues,
J.A.; Barros, A.A. Collection of Czechoslovak Chemical Communications. Accepted manuscript
[1] Pacheco, J.G.; Valente, I.M.; Gonçalves, L.M.; Magalhães, P.J.; Rodrigues, J.A.; Barros, A.A.
Talanta. 2010, 81, 372
[3] Gonçalves, L.M.; Pacheco, J.G.; Magalhães, P.J.; Rodrigues, J.A.; Barros, A.A. Food Additives
and Contaminants. 2010, 27, 175
September, 811, 2010. ISEL - Lisbon 34