Filter Paper Weight Loss

[ajxxx]

need some assistance / technical report with regards to "what causes a filter paper to lose weight"? (standard millipore filter paper of 0.8 microns).

Using the same filter papers to filter aqueous based solution and measuring the pre and post weight (after drying at 100 C for 10 mins) of the filters to determine the solid content remaining on the filters.

Sometimes the filter papers gain weight and sometimes they lose weight? What phenomenon or property of the filter paper maybe causing it to lose weight? just intrigued to know it.

 

[btrueblood]

Are you keeping the filter paper in a dry environment, i.e. in a sealed jar with dessicant? If not, then the filter may be absorbing water over time from ambient humidity, then losing it in the drying step. Alternatively, is there any wash step that uses a solvent that is incompatible with the paper.

 

[EdStainless]

In order to do this correctly you would need to wash and dry the paper before use, filter and then re-wash and dray with your product.


= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[ajxxx]

Thanks Ed...Will try the same.

btrueblood --No we always use hexane so that cannot be an issue. the process would be as below:

1. Pre-weigh filter paper
2. Pass solvent through the filter paper
3. Oven dry filter paper
4. Dry in a dessicator
5. Post Weigh

Am surprised that post weights can be lower? Just curious to know how this could be happening.

 

[cloa]

What's your weighing device? At those tiny weights air pressure may be a factor.

 

[racookpe1978]

Try it 15 times with 15 different "clean" filter papers. (That is, use "pure" or perfectly clean hexane as your "sample")

You should get 15 0.0 results for the difference between initial and final filter paper weights. If you don't you have a problem with your filter/supplier/method.

 

[IRstuff]

Is your filter paper only paper? Are there other fractions that are susceptible to hexane?

TTFN
faq731-376

 

[patprimmer]

I would just try drying the paper to oven dry weight before using it then see is the results become meaningful.

Failing that I would wash the filter in a pure form of whatever solvent was to be used , ie distilled water if testing for solids in water or whatever, then dry to oven dry weight after the wash. Of course take due care if drying of flammable solvents.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

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[tomwalz]

http://www.youtube.com/watch?v=OkYgOcbiFsw

Thomas J. Walz
Carbide Processors, Inc.

http://www.carbideprocessors.com

Good engineering starts with a Grainger Catalog.

 

[btrueblood]

ajxx,

What Ed, myself, and Pat all keep saying, and is missing in your list of steps: make sure the paper is as dry (i.e. dried by the same method) prior to weighing at step 1 as it is at step 5.

With some types of filter paper, and a humid enough day, and a lab balance sensitive to micro-gram levels, you can watch the hydration weight accumulate. Ok, not quite, but I have personally watched and measured such weight change over minutes or 10's of minutes. It's part of qualifying certain lab procedures when precision matters, and it's a step easily forgotten. Like washing beakers, but that is another story.

 

[TomDOT]

Please confirm you have tried the following methods for troubleshooting:

1. Oven dry filter paper
2. Pre-weigh filter paper
3. Pass solvent through the filter paper
4. Oven dry filter paper
5. Dry in a dessicator
6. Post Weigh


1. Pre-weigh filter paper
2. Glare menacingly at filter paper. No solvent, no water.
3. Oven dry filter paper
4. Dry in a dessicator
5. Post Weigh

Please post results of at least 5 replicates for each.

Is your oven clean? Your funnel? Your transfer device (tongs/gloves/fingers)? your scale? Could the filter paper be picking up crud on the bottom? I've seen some pretty darn dirty lab environments in plants.

 

[tomwalz]

Fiber loss

Thomas J. Walz
Carbide Processors, Inc.

http://www.carbideprocessors.com

Good engineering starts with a Grainger Catalog.