Which of the following statements about the Folin phenol reagent are true? (Select all that apply)

The Folin‑Ciocalteu reagent is a mixture of phosphomolybdic and phosphotungstic acids that, when mixed with an alkaline solution, reacts with phenolic compounds to produce a blue‑violet color whose intensity is proportional to the phenolic content. The reaction requires a strongly alkaline medium, usually sodium carbonate, to deprotonate the phenols and allow reduction of the metal oxides. Because the reagent is sensitive to any reducing agent, not only phenols but also sugars, ascorbic acid and some amino acids can also produce a blue color, so the test is not entirely specific. In practice, a small cup of tea is added to the reagent and the resulting blue hue is compared to a standard curve of gallic acid to estimate total phenolics. Thus, the reagent is useful for estimating total phenolic content but must be interpreted with caution due to possible interference.