engleski

Dependence of the total phenolic content measurement values on the procedure used for determination of calibration curve

The total phenols are determined by the modified Folin-Ciocalteu method in such a way that the Folin-Ciocalteu reagent (a mixture of phosphotungstate and phosphomolybdic acid), in reaction with phenolic components reduces and changes colour to the blue [1]. During the measurement of the total phenolic content, the concentration is determined by using the calibration curve of gallic or ascorbic acid. Depending on the choice of the reference compound for determination of calibration curve and on the theoretical approach used for determination of calibration curve, the results may vary considerably. Through the measurement of the total phenolic content of the same type of honey (e.g. acacia), it appears that the total phenolic contents of the same type of honey vary depending on the geographical dispersion, the influence of climatic factors in the current year, the difference between the time of sampling and the time of measurement, etc. However, in addition to these expected and normal variations, the increased disagreement between the measurements in different laboratories could be also due to differences in the process of determination of the calibration curve. Namely, analyzing results in the most frequently cited papers [1-3], significant differences in total phenolic contents were observed. These discrepancies are primarily related to the minimal and maximal range of measurement of gallic or ascorbic acid concentrations in which the calibration curve is determined, compared with the total phenolic contents of samples. Thus, it is possible to produce a calibration curve passing through the starting point, while some authors provide the calibration curve without including the starting point. The influence of these factors is investigated in the analysis of total phenolic contents of 99 honey samples from the South- Eastern European region.

total phenolic content ; calibration curve ; gallic acid ; honey

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