Hello,

I am trying to test the phenol content in my methanolic plant extract, and I am testing two methods.

Method 1: "One ml of 20% sodium carbonate solution was added to 1 ml of the phenolic extract and incubated for 5 min, at room temperature. Then 0.5 ml of Folin Ciocalteo phenol reagent (1:1 diluted with distilled water) was added and incubated for 10 min. At room temperature. The absorbance of the colored solution was read at 735 nm using a spectrophotometer".

Method 2: "100 mcL of the extract was added to 500 mcL of a 1/10 dilution

of Folin–Ciocalteu reagent in water, and then 400 mcL of sodium carbonate solution (7.5% w/v) was added. The mixture was left for 60 min at room temperature, and the absorbance was measured at 765 nm".

However, In both methods, after the incubation time, I got a white precipitate and the colors are off. Because I used a methanolic plant extract I checked to see if I can dissolve gallic acid in methanol also and I read that it is soluble and so I used methanol for both my extract and gallic acid (100% methanol). What could be the problem and what can I change?

Thank you.