guys i have a question... why did you use acetone and not water for pigment isolation??

I didn't.

Just a guess, but are you evaporating off the acetone at any point? If so, it may be used simply because the temperature needed to evaporate off water in a reasonable time would damage the pgiments.

If you're trying to extract hydrophobic photosynthetic pigments then you need to employ a hydrophobic solvent. I'm guessing you'll be using chromatography, thin-layer perchance?

when i conducted the chromatography experiment, acetone is used to break down the cell wall... isn't it?

Physical grinding can usually break up the cell walls perfectly well.