SPI-Pore™ Silver Membrane Media
Enjoy the benefits of an electrically conductive high temperature substrate!
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Scanning electron micrograph of
surface of SPI Silver Membrane
Filter. Horizontal distance is 60µm.
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SPI-Pore™ Silver Membranes
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Chemical formula: Ag
CAS # 7440-22-4
Made from pure silver, SPI Silver Membranes can withstand extreme
temperature, pressure and solvents without collapsing, tearing, curling,
or dissolving. More than tough, they are very smooth, extremely thin
(.002" thick/51µm), and uniformly porous; they are also reusable
(cleaned by oxygen isotropic plasma etching, ignition procedures, or
sometimes just by simply back-washing). The most convenient if not also
the best way for the cleaning for reuse of silver membrane filters is with
the use of the SPI Plasma Prep
II unit. The silver membrane filters are available from pore sizes of
0.2 to 5µm. For smaller pore sizes, one would need to use the
aluminum oxide membrane filters.
Actually, we can offer
quite a bit of other information about the SPI Silver Membrane filters
which could be of additional value if you are comtemplating the use of the
silver membrane filters for your work.
Although the SPI Silver Membrane filters are used in a large number and
variety of applications, their unique chemical and thermal stability is
especially valuable for those applications involving aggressive fluids
and/or high temperatures. They are ideal collection media for analysis of
crystalline silica by x-ray diffraction and for analysis or organic
materials by other instrumental techniques, such as the analysis of
polyaromatic hydrocarbons (PAH). These are all in addition to the very
popular and common
application in the scanning electron microscope (SEM)
laboratory since with a conductive substrate, one normally has a greatly
reduced need to apply a conductive metal coating, something that can end
up covering up important structure that other wise would be resolved.
The silver membrane filters are also used for high temperature filtration,
sterilization, removal of microbial and particulate contaminants from
fluids, under pressure, and in caustic liquids and gases. (Note: Silver
membranes are not resistant to nitric and sulfuric acids or cyanide
solutions). The unique combination of
physical properties and retention and flow rates for the SPI Silver
Membrane filters have led to an enormous number of different and diverse
applications.
Life Science Researchers . . .
will find SPI Silver Membranes particularly useful for specimen
preparation. Besides reducing the need to metallize specimens,
they provide:
- Highly conductive surface for mounting, for SEM, including biological
specimens, especially when being collected from suspension (e.g. individual
cells or small groups of cells, small particles, etc.).
- Rigid support for direct SEM or LM viewing of specimens
- Critical point drying substrate (behaves like a polymer membrane
filter) of collected particular samples for later viewing, on the filter,
by SEM (or LM).
- Conductive surface often times leads to reduction or elimination of
need for conductive metal for SEM observation, an advantage of particular
importance to the life sciences researcher.
- Excellent heat transfer surface for dimensional preservation of
specimens during freeze-drying.
- Bacteriostatic properties
Determining Free Silica: An Application Following NIOSH Methods
Air-jet milled quartz (SiO2) used here to
simulate quartz in respirable industrial dusts, illustrates the utility of
SPI Silver Membranes for this analysis. The SPI Supplies brand of silver
membrane filters meet the requirements of NIOSH procedures for the
measurement of free silica.
SEM images show silver filter surfaces without and with particulate
SiO2. Corresponding x-ray diffraction
patterns identify components before/after dusting with
SiO2.
Low x-ray background is evident and diffraction lines for Ag do not
interfere with measurements of quartz line as do other substrates.
* Bumstead, H. E. 1973 "Determination of Alpha-Quartz in the
Respirable Portion of Airborne Particulates by X-Ray Diffraction".
Amer. Ind. Hyg. Assoc. J. 34, 150-58.
* NIOSH Manual of Analytical Methods 1977. Method No.: P&CAM 259.
Appendix 1, Vol. 1.
Supt. of Documents, U.S. Government Printing Office.
Washington, D.C. 20402 GPO #017-003-00267-3.
Other Research Applications:
- Filtration of alcoholic beverages
- High temperature processing of viscous materials
- Performing mild chemical digestion directly at filter surface
- High temperature stack sampling
- High temperature sterilization procedure
- Filtration involving organic solvents
Holding the membrane filters:
All membrane filters, offered by SPI Supplies, irrespective of their
construction, must be used in conjunction with a
specially made membrane filter holder.
Still need some additional technical information about the SPI Silver
Membrane filters? It is all here!
Storage and shelf life:
So far as we know, there is real "expiration date" for the SPI-Pore silver membrane filtration
media. However, we also know that oxides and other extraneous compounds can form with time
depending on the environment in which the silver membranes are stored. Such silver compounds
which may form on the surface are primarily cosmetic in nature and do not affect the pore
structure or membrane filtration performance. However, since nothing is forever, we have
put an expiration date of five years onto the SPI Pore Silver Membrane Sheets. There should
be at least three years remaining before this somewhat arbitrary determined expiration date
in order to make sure that there is some time limit to which one could expect the performance
to be as if they were brand new membranes.
Product availability:
The SPI-Pore Silver Membrane Filtration Media is available in both disc and large sheet format.
The discs are die-cut and in ready-to-use form with any standard disc filtration apparatus
(e. g. funnels, cannisters, etc.). The large sheet format is offered for those needing custom
cut sizes and who would find it more economical to do their own small quantity cutting in
their own facilities.
Disc format:
Large sheet format
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Wednesday May 14, 2008
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