I got confused about your question. Do you want a solvent to dissolve petroleum ether and ethyl acetate but not PS?

Try acetonitrile.

Yes, please refine your question

So you mean DCM is dissolving your 96 well plate? you need alternative to DCM for dissolving your PS ?

Try DMSO, as I believe you will carry out some assay reactions

DMSO is 96 well plate friendly.

Perhaps is better to change the material of the plate or use glass coated 96 well plate.

 searching in the web I found: A convenient, cost-effective option for eliminating extractable background contaminants when sampling from microplates.   WebSeal Plate+ 96-Well Glass-Coated Microplates offer resistance to solvent extraction similar to glass while retaining the handling advantages of polypropylene. They are also an ideal choice for applications where standard plastic microplates are not suitable and eliminate the need to use limited volume glass inserts

m sorry for the confusion caused. mr adli is correct.however my compound is non Polar,so is there an alternative brsides dmso and acn as i've tried dmso at 10% concentration and failed to dissolve it

Use other chlorinated hydrocarbon solvents such as 1,2-dichloroeathane or 1,1,1-trichloroeathane.

all the chlorinated hydrocarbon solvents is going to dissolve the PS plate, if you dont mind to change the PS plate, try glass plate, but i dont know if you should/chould because its kinda hard to understand this question. 

The not chlorinated solvents, like tetrahydrofuran or dioxane, probably work.

you can try check non polar solvent

You try n-Hexane?

long alcohols, iso-propanol or butanol

THF, Et2O, EtOAc should be convenient solvents

you can try toluene or benzene

Solvent to dichloromethane without its ability to dissolve polystyrene , one can try toluene or xylenes

thank you for the suggestions :D