It is doubtful that NaOH is "trapped" in naptha, nor contaminating your sample. Na+ and OH- will always magnetize in your polar aqueous layer (water). The goods will always migrate to the non-polar layer (naptha). If one is concerned about NaOH remaining in your naptha extractions then simply...

I know that if one were to deacetylate melatonin one would get mexamine. I know that if one were to dimethylate mexamine one would get honey.