Filtration / Glassware

Sintered disc or sintered frit filtration funnels – how to care for sintered discs? When to select a sintered disc funnel? What do sintered disc grades mean?

Vacuum filtrations using a Buchner flask and funnel with a vacuum pump are commonly used to isolate a solid of interest from a liquid.

Most commonly a porcelain Buchner funnel with a filter paper placed on top is used, but in some instances a sintered disc funnel is more appropriate.

But when would you select a sintered disc funnel? And how should a sintered disc filter funnel be cleaned and cared for?

Buchner funnel with sintered disc
Buchner filtration funnels with a glass sintered disc, aka sintered frit

When to choose a sintered disc

The main reason a sintered disc would be chosen is when you are working with corrosive chemicals that would damage filter paper.

The sintered discs in Pyrex and Quickfit glassware are made entirely of Pyrex borosilicate glass, meaning they are resistant to a wide range of corrosive chemicals.

As the discs are not affected by ammonia, sulphuric acid and other solvents which can be damaging to filter paper, a sintered disc is a good choice if you are using these products.

 

How to care for sintered disc glassware

When using a new sintered disc you should rinse it with mild Hydrochloric Acid solution, then rinse again several times with distilled water, to remove any residual glass dust particles left over from manufacture.

After each use rinse thoroughly with water to keep the disc clean from particulates.

As with all Pyrex glass, the discs can withstand heating and cooling but take care that this is done slowly and uniformly to avoid thermal shock.

 

What do the porosity grades of sintered discs mean?

Sintered discs are supplied in various porosity grades – these related to the range of pore sizes present within the disc.

At a practical level this means particles stopped by the disc will generally be at the upper end of the range.

The table below shows the porosity grades and actual pore sizes;

Porosity Grade ISO 4793 Designation Pore Index (microns µm) Principal Uses
0 P250 160 – 250 Coarse filtration, gas dispersion, support for other filter material (e.g. column chromatography)
1 P160 100 – 160 Coarse precipitate filtration, gas dispersion, coarse grain material filtration
2 P100 40 – 100 Medium and crystalline precipitate filtration, medium filtration and washing of gases
3 P40 16 – 40 Analytical work with medium precipitates
4 P16 10 – 16 Analytical work with fine precipitates
5 P10 4 – 10 Bacteria filtration

 

For more information on Buchner funnels with sintered discs, or other laboratory glassware, follow the links above or contact us with your questions;

 

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