Determination Of Total Phenolic Content From Plant Extracts Used In Cosmetic Purpose

Spectrometric analysis belongs to a group of measurement methods used for their simplicity and large selectivity to solve various problems of analytes. The total phenolic content of different plant extracts used for cosmetic purpose was determined by a slightly modified version of traditionally Folin-Ciocalteau method. The objective of this work was the validation of UV-Vis spectrometric method, investigation of uncertainty sources when measuring gallic acid concentration and evaluation of the calibration equation effect on measurement uncertainty of UV-Vis spectrophotometer. Validation was performed by studying analytical curve linearity (R-2=0.9995) and range (37.5 - 225 mg L-1), estimated limit of detection (LOD, 0.11mg L-1) and limit of quantification (LOQ, 0.37 mg L-1), precision (%RSD, 0.14 - 1.34), recoveries (83-110%) and stability (%RSD, 0.8 - 2.83). To obtain more representative values for precision, recoveries and stability simultaneous replicates at different times, on different matrices including plant (marigold, chamomile and lavender) were performed during the study period. The validated method was successfully applied to determine TPC in marigold extracts. For chamomile and lavender extracts, the spectrometric method presented only acceptable precision, among all the performance parameters studied. The sources of the gallic acid concentration measurement uncertainty include purity, volume of flasks, mass and the calibration equation. The results indicated that the uncertainty components from purity were the smallest. An important source of the uncertainty was the mass. The volumes of the volumetric flasks had only modest effect on the uncertainty. The contribution of calibration equation is the greatest from all sources.