I know this post is 3 years old, but I figured I would answer b/c when I was starting I had alot of questions about filters and the membrane types in them that mostly all went unanswered. It's very difficult to get help with any question in this area i've noticed, just like the post above going completely unanswered for 3 years now. It really makes me wonder if everybody posting on the subject of conversions and filtering their final solutions has actually ever done it at all, or they're just reading about it, thinking about doing it and answering questions on the subject from only their research and not their experience.
From my experience and trial and error procedures, I've noticed that the best filter membrane, by far, for oil solutions is NYLON. You can also use PVDF, although you need to take into account the speed of which the different membranes can process your solution. From what I"ve used, the PVDF membrane, especially in .22micron has a speed that is extremely exaggerated on many websites like the Whatman homepage. To me, using this filter with a GSO type solution is about as bad as watching the grass grow. That is my best description of how slow PVDF is in filtering in a .22micron size. .45 microns in PVDF allow for twice this speed, but it's like doubling the speed of a turtle. It's still gonna be way too dam slow for myself.
As far as syringe filters, not bottle top or filter units, the best ones i've found so far is "Whatman's AutoVial System." They're only available in 5 or 12 ml sizes, which sucks, but I"m still able to filter 50ml's of solution with these 12ml autovials in about 20 or 30 mins. If I wanna get it super clean I can filter 50mls twice in under an hour everytime. You can also still use these autovials with a caulk gun. Just have to use a lil improv. and put a vitamin lid at the end of the gun with a good sized washer to strengthen the area at the end of the autovial or syringe, where most of the pressure is being exerted on the unit. I also think it helps to put either a 16 or 18 guage tip on the autovial because the end tip isn't exactly like a syringe and is a lil recessed inside the end of the unit where the end of the tip is flush with the bottom of the autovial. But like I was saying, it has taken me hours to filter 50mls of an oil solution with a PVDF filter.
I ABSOLUTELY HATE THEM!!
PVDF is also supposed to be better at removing particulates than nylon is, but I've had solutions I've filtered once and twice with the PVDF and NYLON both and compared them after once and after twice and I think personally, the NYLON filtered solution always looks alot better. Even with a .45 micron NYLON after filtering twice, which still takes hardly no time, I have never had even one small particulate left in my final solution. I have had them several times w/ .22 micron PVDF though. Alot of ppl will advise you to filter your solution while it's still hot or at the least while warm. With the autovials, your flow rates don't differ enough to notice whether hot or cold so I just mix all my ingredients, get whatever i'm making to the required melting point temp., keep this same temp for a period of 30mins or so, remove and let cool. As soon as it cools to room temp, I will then filter my stuff the 1st time. This will remove 75% or more of the things u don't want in your solution. I will then let that solution set. After it has set for a descent while, which is never over 24 hours. I will filter again. My final solution is always professional looking with nothing but good crystal clear liquid left. At 1st I was worried the stuff that settles to the bottom when cool could be some of my prop or hormone, but after alot of research once you get your solution to the melting point and the whole solution clears and stays at this temp for a lil while, your BB/BA or solvent/co-solvents purpose is to keep this hormone suspended in the solution when it is cool so what your seeing settle, if done correctly, is not your desired hormone. It is your fillers/binders/estrogen that is settling. If your solvents/co-solvents arent correct though, your solution can "crash" and then your hormone will settle and unsuspend from your solution and then would be filtered out. So make sure your ratios are correct and it'll come out great.
PES is for water based solutions, not oil based solutions!! Don't try and filter your prop/enanthate/cypionate/deca etc..... oil based solutions through PES, it doesn't work. It will work for test suspension, but again test susp. is water based, so there ya go!