Development of a multivariate calibration model for the determination of dry extract content in Brazilian commercial bee propolis extracts through UV–Vis spectroscopy

• Step of centrifugation is required to determine the dry extract content.
• Residue obtained after centrifugation is composed mainly of waxes.
• The contents of dry extract of propolis extracts were estimated by PLS.
• The detection of outliers was performed on the optimization of multivariate calibration.
• The proposed method can be used as a screening method in routine analysis.

This study had the objective of determining the content of dry extract of commercial alcoholic extracts of bee propolis through Partial Least Squares (PLS) multivariate calibration and electronic spectroscopy. The PLS model provided a good prediction of dry extract content in commercial alcoholic extracts of bee propolis in the range of 2.7 a 16.8% (m/v), presenting the advantage of being less laborious and faster than the traditional gravimetric methodology. The PLS model was optimized with outlier detection tests according to the ASTM E 1655-05. In this study it was possible to verify that a centrifugation stage is extremely important in order to avoid the presence of waxes, resulting in a more accurate model. Around 50% of the analyzed samples presented content of dry extract lower than the value established by Brazilian legislation, in most cases, the values found were different from the values claimed in the product’s label.

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