Flow injection chemiluminescence determination of the total phenolics levels in plant-derived beverages using soluble manganese(IV) Original Research Article

This study established a flow injection (FI) methodology for the determination of the total phenolic content in plant-derived beverages based on soluble manganese(IV) chemiluminescence (CL) detection. It was found that mixing polyphenols with acidic soluble manganese(IV) in the presence of formaldehyde evoked chemiluminescence. Based on this finding, a new FI-CL method was developed for the estimation of the total content of phenolic compounds (expressed as milligrams of gallic acid equivalent per litre of drink) in a variety of wine, tea and fruit juice samples. The proposed method is sensitive with a detection limit of 0.02 ng mL−1 (gallic acid), offers a wide linear dynamic range (0.5–400 ng mL−1) and high sample throughput (247 samples h−1). The relative standard deviation for 15 measurements was 3.8% for 2 ng mL−1 and 0.45% for 10 ng mL−1 of gallic acid. Analysis of 36 different samples showed that the results obtained by the proposed FI-CL method correlate highly with those obtained by spectrophotometric methods commonly used for the evaluation of the total phenolic/antioxidant level. However, the FI-CL method was found to be far simpler, more rapid and selective, with almost no interference from non-phenolic components of the samples examined.