Table 1.

Methods to quantify phenolic compounds.

Assay	Types of phenolics	Description	Reference
Folin-Ciocalteu assay	Total phenolic acids	An assay based on electron transfer (ET) in which oxidation of phenolics by Folin-Cioalteu reagent gives a colored product at 750 nm	[12]
CuO oxidation-GC	Lignin-derived phenolics	A method in which oxidation of lignin by cupric oxide yields single-ring phenol compounds (vanillyl-, syringyl-, and p-coumaryl units), followed by gas chromatography Also, the acid to aldehyde ratio can be used to estimate the state of decomposition of lignin	[13]
HPLC	Individual	A separation technique in which a mixture of phenolics produces different retention times depending on their affinity to the stationary phase	[14]