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Definitive screening designs and latent variable modelling for the optimization of solid phase microextraction (SPME): case study-quantification of volatile fatty acids in wines
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Advisor(s)
Abstract(s)
In the present study, we apply the recently proposed Definitive Screening Designs (DSD) to optimize HS-SPME
extraction in order to analyze volatile fatty acids (VFA) present in wine samples. This is the first attempt to
apply this new class of designs to one of the most well-known and widely applied extraction techniques. The latent
structure of the responses is also explored for defining the optimal extraction conditions. DSD is a new screening
design with the potential to significantly reduce the number of experiments required to estimate the model pa rameters and to establish the optimum operation conditions. Therefore, there is an obvious interest in assessing
the benefits of DSD in practice. In this work, this design framework is applied to the simultaneous optimization of
seven extraction parameters (responses). Both qualitative and quantitative extraction parameters are considered,
in order to test the flexibility of DSD designs: a two-level qualitative variable, the fiber coating, and six quanti tative variables, namely the pre-incubation time, the extraction time and temperature, the headspace/sample
volume, the effect of agitation during extraction and the influence of the ethanol content (sample dilution).
Optimization of analytes' chromatographic responses was carried out both individually (response by response)
and altogether, by modelling the responses in the latent variable space (i.e., explicitly considering their under lying correlation structure). In the end, a consensus analysis of all perspectives was considered in the definition of
the overall optimal extraction conditions for the quantification of VFA in fortified wines. The solution found was
to use a DVB/Car/PDMS fiber, 10 mL of samples in 20 mL vial, 40 min of extraction at 40 C. The analysis also
revealed that the factors incubation time, agitation and sample dilution do not play a significant role in explaining
the variability of extraction parameters. Therefore, they were set to the most convenient levels. The methodology
followed was thoroughly validated and the following figures of merit were obtained: good linearity (R2 > 0.999,
for all compounds), high sensitivity (LOD and LOQ are close or below the values found in literature), recoveries of
approximately 100% and suitable precision (repeatability and reproducibility lower than 7.21% and 8.61%,
respectively). Finally, the optimized methodology was tested in practice. Several wine samples were analyzed and
the odor activity value calculated to facilitate the identification of their importance as odor active compounds in
different aged fortified wines. This work demonstrates the benefits of using DSD and latent variable modelling for
the optimization of analytical techniques, contributing to the implementation of rigorous, systematic and more
efficient optimization protocols.
Description
Keywords
Definitive Screening Designs Principal component analysis HS-SPME Optimization Volatile fatty acids Fortified wines Weighted least squares . Faculdade de Ciências da Vida Faculdade de Ciências Exatas e da Engenharia
Citation
Pereira, A. C., Reis, M. S., Leça, J. M., Rodrigues, P. M., & Marques, J. C. (2018). Definitive screening designs and latent variable modelling for the optimization of solid phase microextraction (SPME): case study-quantification of volatile fatty acids in wines. Chemometrics and Intelligent Laboratory Systems, 179, 73-81. https://doi.org/10.1016/j.chemolab.2018.06.010
Publisher
Elsevier