Uncertainty estimation for total antioxidant capacity measurement of apple juice using main CUPRAC method

The estimation of uncertainty –taking into account all sources of error- is an important tool allowing the identification the influence of each stage of the analytical procedure on the overall quality of the results. Measurement uncertainty - reported with the measurement result - is a parameter that indicates the distribution of the probabilities attributable to the measurement results. The aim of this study is the first time estimation of measurement uncertainty for total antioxidant capacity (TAC) of a Turkish commercial apple juice by the main CUPRAC method that uses Cu(II)-neocuproine (Nc)/Cu(I)-Nc redox couple to measure the TAC levels of various biological fluids and foods. The individual source of uncertainties such as repeatability, calibration curve, concentration of the trolox (TR, reference) solutions, pH, temperature and redox factor in the CUPRAC reaction between TR and Cu(II)-Nc were considered in this work. It was found that the measurement uncertainty was dominantly affected by the total CTR standard solution (ur(CTR) =0.0124). Each uncertainty parameter was evaluated separately, and the relative expanded uncertainty value was calculated as ±3.05% with a 95% confidence interval (k=2).