Filtration flow rate by filter membrane

[OffendHand]

I'm using a filter holder, vacuum flask, mechanical vacuum pump, .22 micron 47mm PTFE filter membranes, and off-the-shelf (not USP) MCT oil. Filtration is extremely slow at room temperature with plain oil (e.g., not heated, no solvents, no hormone; literally just testing the filtration setup to make sure that there are no air leaks or filtration failures). By "extremely slow", I mean 3-4 drops/second once the filter membrane is saturated, rather than a stream or even a trickle. I do not have an in-line vacuum gauge, so I'm not sure exactly how much vacuum I'm pulling.

I assume that this will speed up somewhat once I have solvents in the oil and it's warmer (>125F), but I don't know how much. Thankfully no-name Chinese filter membranes are pretty cheap compared to disposable bottle-top filters.


So, several questions.

1) Is this extremely slow rate of flow expected under these conditions (room temp, no solvent, etc.)? Other threads seem to indicate that it is.

2) Would switching to a nylon filter membrane improve flow rate, and would the membrane survive the benzyl alcohol and benzyl benzoate?

2) Should I consider doing two passes, a first with a coarser filter (.45 micron or larger pore size), reheat my solution, and then do a final pass for sterility?

While I'm tempted to switch to a pressure-driven system with a peristaltic pump, that's more suited for production volumes (largely due to the up-front costs), and I'm strictly personal use.

 

[jJjburton]

I'm using a filter holder, vacuum flask, mechanical vacuum pump, .22 micron 47mm PTFE filter membranes, and off-the-shelf (not USP) MCT oil. Filtration is extremely slow at room temperature with plain oil (e.g., not heated, no solvents, no hormone; literally just testing the filtration setup to make sure that there are no air leaks or filtration failures). By "extremely slow", I mean 3-4 drops/second once the filter membrane is saturated, rather than a stream or even a trickle. I do not have an in-line vacuum gauge, so I'm not sure exactly how much vacuum I'm pulling.

I assume that this will speed up somewhat once I have solvents in the oil and it's warmer (>125F), but I don't know how much. Thankfully no-name Chinese filter membranes are pretty cheap compared to disposable bottle-top filters.


So, several questions.

1) Is this extremely slow rate of flow expected under these conditions (room temp, no solvent, etc.)? Other threads seem to indicate that it is.

2) Would switching to a nylon filter membrane improve flow rate, and would the membrane survive the benzyl alcohol and benzyl benzoate?

2) Should I consider doing two passes, a first with a coarser filter (.45 micron or larger pore size), reheat my solution, and then do a final pass for sterility?

While I'm tempted to switch to a pressure-driven system with a peristaltic pump, that's more suited for production volumes (largely due to the up-front costs), and I'm strictly personal use.

Yes warming the oil will make it substantially faster also adding BB, its a huge difference.

 

[Hermetically]

I think the problem is on your bottle top filter funnel can you show me picture how it looks ?
And depends what vacuum pump you using sometime you need for these filters stronger pump with adjustable valve .

 

[OffendHand]

I think the problem is on your bottle top filter funnel can you show me picture how it looks ?
And depends what vacuum pump you using sometime you need for these filters stronger pump with adjustable valve .

It will take me a day or two to get photos. It's Millipore Hydrosol filter holder (stainless steel instead of fritted glass). I've already replaced the PTFE seal around the lock ring and under the filter holder. I have just gotten a new #8 drilled rubber stopper since the old one was feeling a bit crunchy (the stopper creates the seal between the filter holder and the vacuum flask).

I've also ordered both hydrophilic and hydrophobic PVDF filter membranes to see if the PTFE is the issue. PTFE should be compatible with both BA and BB, but being naturally hydrophobic might make filtration harder than necessary.

The vacuum pump could be a weak point. While it worked well enough a number of years back when I was using disposable .22 micron PES bottle top filters (PES is not compatible with BA/BB; I would get good flow to start, and then it would quickly become very, very slow), it's still a refrigerant pump rather than a vacuum pump designed for using in a lab.

From further reading, given that nylon will bind to proteins, it sounds like I do not want to use a nylon filter.

 

[Hermetically]

PES is not compatible with BA/BB On his own but when you mix it with MCT oil usp grade or Mig840 it is ok .
On 50 degrees Celsius you can try
First with 0.45 micron than with 0.22
I have like your filter funnel and flask was aways leaking and problem with the flow rate .
You definitely need stronger pump and do it aways when the oil is warm over 50C
If the solution is over 1L
I suggest you use Bottle top filter 0.22um 1L
With Glass Media Bottle GL45 cap which is sealed perfectly and doesn’t let air to go out

 

[OffendHand]

I'll move the pump farther away from my flask setup so I can hear more clearly, but I'm pretty sure that it's not leaking a significant amount. I definitely need to get a vacuum gauge to mount in-line so I can see just how much vacuum I'm pulling from the pump. I don't recall what the CFM is, and it's not an oil-free pump.

I've ordered hydrophobic PVDF filter membranes, and I'm waiting for my hydophilic PVDF filter membranes to arrive. I suspect that using a hydrophobic membrane might be part of what's really slowing me down; it looks like they're mostly supposed to be used for gaseous filtration.

I'd prefer to avoid getting disposable bottle-top filters if I can; I'm doing fairly low volume--under 250ml at a time--and it just seems very wasteful. Are there any bottle-top filters that can be sterilized and use a replaceable filter membrane?

 

[mochul]

I used ptfe syringe filter for oils which is hydrophone and it filters very fast. However, I tried making sterile water with the same filter and it took ages to filter 30ml pure water. The problem is not your type of filter. Hydrophobe is for oily solutions and hydrophilic for aqueous

 

[OffendHand]

I used ptfe syringe filter for oils which is hydrophone and it filters very fast. However, I tried making sterile water with the same filter and it took ages to filter 30ml pure water. The problem is not your type of filter. Hydrophobe is for oily solutions and hydrophilic for aqueous

Hmmm. I wonder why I'm having an issue with PTFE filter membranes specifically in a vacuum filter then?

Using a hydrophilic PVDF .22 micron membrane, tap water filters quite quickly (and my tap water is dirty as shit). So I don't think that the filter holder is the direct issue.

I'll try the same type of membrane for a warm MCT + 20% BB + 2% BA, and then try the same solution in a hydrophobic PVDF membrane, and the original PTFE membrane. It might be that the MCT is too thick when it's cold, it might be too thick without being thinned down by 20% BB (which appears to be the standard for pharmaceutical test e), it might be both together.

I might need to switch to GSO, which is what I used to use.

 

[OffendHand]

I'm starting to think that I should have stuck with disposable bottle top filters. :/

 

[OffendHand]

A significant part of the issue seems to be vacuum line size. When I switched to an older, larger diameter vacuum line, flow rate increased significantly. It's not fast by any stretch of the imagination, but it's fast enough. I think.

 

[patriotmuscle1]

My first guess is not enough vacuum .. either maybe pump is too weak or you ha e a vacuum leak somewhere,, at a connection, pin hole in hose or not a good seal where filter is clamped.
I feel like I've had something similar happen years ago and it was where the funnel and flask joined and met filter it's self..

I took seran wrap and placed it close to joint while running just plain oil and looked for the wrap to be drawn/sucked into seam..

 

[OffendHand]

I'll give that a try, see what shakes out.

I've also just changed the oil in my pump; it was well past due. That might have been affecting it too, IDK yet.

 

[patriotmuscle1]

I'll give that a try, see what shakes out.

I've also just changed the oil in my pump; it was well past due. That might have been affecting it too, IDK yet.

Let me know what fixes your issue .. just good to know for troubleshooting in the future

 

[topchef123]

Estou usando um porta-filtro, frasco de vácuo, bomba de vácuo mecânica, membranas de filtro PTFE de 0,22 mícron e 47 mm e óleo MCT pronto para uso (não USP). A filtragem é extremamente lenta em temperatura ambiente com óleo puro (por exemplo, não aquecido, sem solventes, sem hormônio; literalmente, apenas testando a configuração de filtragem para garantir que não haja vazamentos de ar ou falhas de filtragem). Por "extremamente lento", quero dizer 3-4 gotas/segundo quando a membrana do filtro estiver saturada, em vez de um fluxo ou mesmo um gotejamento. Não tenho um medidor de vácuo em linha, então não tenho certeza de quanto vácuo estou puxando.

Imagino que isso vai acelerar um pouco quando eu tiver solventes no óleo e ele estiver mais quente (>125F), mas não sei o quanto. Felizmente, as membranas de filtro chinesas sem marca são bem baratas em comparação com os filtros descartáveis de garrafa.


Então, algumas perguntas.

1) Essa taxa extremamente lenta de fluxo é esperada sob essas condições (temperatura ambiente, sem solvente, etc.)? Outros tópicos parecem indicar que sim.

2) A troca para uma membrana de filtro de náilon melhoraria a taxa de fluxo e a membrana sobreviveria ao álcool benzílico e ao benzoato de benzila?

2) Devo considerar fazer duas passagens, uma primeira com um filtro mais grosso (tamanho de poro de 0,45 mícron ou maior), reaquecer minha solução e depois fazer uma passagem final para esterilidade?

Embora eu esteja tentado a mudar para um sistema de pressão com uma bomba peristáltica, ele é mais adequado para volumes de produção (em grande parte devido aos custos iniciais) e é estritamente para uso pessoal.

Hello, friend! Do you purchase sterile membranes? I ask because I can't find sterile ones in my country.

 

[maxtom]

So hydrophilic or hydrophobic membrane?

 

[Dxt25]

So hydrophilic or hydrophobic membrane?

As per @narta hydrophilic does both water and oil

 

[Sampei]

I wonder how can you sterilize your membrane when I couldn't find for the love of god anywhere sterile membrane for vacuum filters.

Bottle top is the way to go 100%

 

[Dxt25]

I wonder how can you sterilize your membrane when I couldn't find for the love of god anywhere sterile membrane for vacuum filters.

Bottle top is the way to go 100%

Bottle top is so much faster but I still refilter with syringe filters into sterile bottles one more time. I was thinking about this yesterday on syringe filters, how can you sterilize them? Push some Ba through them?

 

[Sampei]

Bottle top is so much faster but I still refilter with syringe filters into sterile bottles one more time. I was thinking about this yesterday on syringe filters, how can you sterilize them? Push some Ba through them?

Syringe filters come sterilized unless you bought unsterile syringe filters and those are useless for us