A reproducible, rapid and inexpensive Folin-Ciocalteu micro-method in determining phenolics of plant methanol extracts

A new combination among time, temperature, alkali and alcohol is described for the spectrophotometric determination of small concentrations of phenolics in methanol extracts from plant. It is a variation of the classical Folin-Ciocalteu (F-C) method, but the reaction conditions are optimized in order to eliminate methanol interferences in the assay. Alcohol concentration and reaction time limits have been evaluated as 4% methanol (v/v) and 20 min at 40 degrees C, using a 5% (w/v) sodium carbonate solution. This F-C micro-method is reproducible, quick, inexpensive and particularly helpful if it works with numerous samples or on a small scale, such as during the setting up of an experimental procedure of alcoholic extractions.