Dear colleagues, I need to analyze phenols (tannin and lignin) on coffee processing wastewater, following the method 5550 B from Standard Methods for the Examination of Water and Wastewater. It is a colorimetric method, based on the principle that lignin and tannin contain aromatic hydroxyl groups that react with Folin-Ciocalteu′s phenol reagent to form a blue color.

According to the literature, phenols are considerably present on coffee fruits skin, which makes it necessary to extract phenols.

I found different papers proposing different methodologies, including liquid-liquid, liquid-solid, microwaves, and ultrasound extraction methodologies.

I am particularly considering using methanol to perform the extraction.

I was wondering if there's a better way to extract phenols (especially, but no restricted to tannin and lignin) from this kind of effluent or other effluents related.