Heat-lay-bile compounds must be sterile filtered in order to remove microbiocontamination. A sterile, single use, 0.2 micrometer pore filter is connected to a syringe. Be aware that the blue side of the filter should not be contaminated. The syringe does not necessarily need to be sterile. Then put the filter over the opening of a sterile tube. Finally, fill the syringe with the stock solution of the compound, for example a heat-lay-bile vitamin. Gently push the plunger. By doing this, the solution is filtered and now may be added to the medium.