What is the Y value to find out total phenolic content?

I am estimating the total phenolic content (TPC) of 70% ethanol plant extract using the Folin-Ciocalteu method. My samples are rich in phenolics, so I need to dilute them to proper concentration before the measurement. I observed that when I am using 70% ethanol to dilute the samples I obtain higher TPC value then when I am using water. The rest of the method remains the same. What could be a reason of this variability? 

I want to do a thin layer chromatography of an aqueous extract of plant, I used a combination of ethyl acetate and cycliheximide, no proportion gave a separation of the compounds of the extract. I tried different combinations of water and methanol, no more separation. what other solvents could you suggest to me?

Is it possible in the plant extracts to have a total phenolic content lower than the total flavonoid content ? whereas many flavonoids are also phenolic compounds.

About plant extraction methods.

Which is best solvent and most suitable extraction method for plant phenolics?

After the synthesis of my nanoparticles using plant extract to bio-reduce silver, what solvent can I use to dissolve the already dried nanoparticles for biological assay?

to analysis the phenolic composition of some plants extracts 

I need to isolate phenolics from the plant extracts. I had tried it with amberlite xad, but I didn't get sufficient separation. Can any one suggest better separation method for phenolics (without using C-18 or sephadex)?