08 TECHNICAL INFORMATION | PRODUCT-SPECIFIC SECTION
DURAN® filtering apparatus
The filter apparatus has virtually universal applications with regard to the chemicals to be filtered because the medium only comes into contact with glass and PTFE. The graduated funnel simplifies dosing and analysis. The tried-and-tested DURAN® filtering flask and PTFE hose connection enable safe working in the laboratory. Thanks to the PTFE plate holder, porous glass plates with different porosities can also be used in addition to the split sieve. Filter paper, membrane filters (47 mm) or just glass filters can be used for filtration. The replaceable plates and the PTFE adapter in conjunction with the clamp enable rapid changing of porosities or replacement of filters. Cleaning has been significantly simplified compared to a traditional filter funnel as the filter plate can be cleaned quickly and easily from both sides. Recommendations Coarse and fine and also analytical filtration can be carried out thanks to the available porosities of 10µm – 160µm. Furthermore, the filtration appliance is also suitable for the filtration of HPLC media, testing for bacterial contamination, residue analysis and the filtration of other media.
Porosity
Porosity measurement is by the Bechhold bubble pressure method, which is widely described in the literature 1 . In the interests of rapid filtration every effort is made to produce filter disks with as many open pores as possible without blockages or closed cavities. This is one of the areas where DURAN® glass filters stand out. Prerequisite for the successful use of glass filters is selection of the correct porosity. In this respect, the following table lists details of six porosity ranges with indications of their main areas of application. A point to be borne in mind is that the filtration equipment should ideally be selected to ensure that the nominal size of the largest pore is somewhat smaller than the smallest particles to be filtered out. This will prevent infiltration of particles into of the pores. For quantitative analysis applications, porosity 3 or porosity 4 glass filtration apparatus is used almost exclusively. Different working methods often contain different porosity indications here for the same materials. This is because different processes used in the production of precipitations for gravimetric analysis often result in different grain sizes.
1 Frank, W.: GIT (1967) Iss.7 pp. 683 – 688
Porosity classes:
ISO 4793
Porosity
Nominal max. pore size µm
Areas of application Gas distribution
0 1 2 3 4 5
P 250 P 160 P 100 P 40 P 16 P 1,6
160 – 250 100 – 160 40 – 100 16 – 40 10 – 16 1.0 – 1.6
Dispersion of gas in liquids Preparative fine filtration
Analytical filtration
Analytical fine filtration
Feinstfiltration
ASTM E128-99
Porosity
Nominal max. pore size µm
Areas of application
EC Extra Coarse
170 – 220 40 – 60 10 – 16 4.0 – 5.5 2.0 – 2.5 0.9 – 1.4
Gas distribution
C
Coarse Medium
Dispersion of gas in liquids Preparative fine filtration
M
F
Fine
Analytical filtration
VF Very Fine UF Ultra Fine
Analytical fine filtration
Ultrafine filtration
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