Not sure whether naptha leaches plastic the same way IPA and acetone will, but I would recommend not using plastic. When extracting, you want your naptha to be hot, which by itself may melt the plastic. I like to use droppers when separating layers, but glass ones purchased from Walmart or a drug store. They're like $2 for a pack of two, one straight tip, and one angled tip. The angled tip is great for separating layers. To me, extracting with an inert material gives me peace of mind, especially when consuming the final product. Save yourself the potential hazard to your body, and use glass.