applications

One of the more intriguing applications for our nylon membranes is in fuel testing, where nylon is the preferred media for the testing methods described by ASTM standards D6217 and D5304.

ASTM D6217 governs particulate contamination testing by laboratory filtration of middle distillate fuels. Fuel samples are vacuum filtered past Nylon membrane filters (0.8 micron) and the particulate contamination level is determined by weighing the membranes.

ASTM D5304 sets a standard test method for assessing the storage stability by oxygen overpressure of middle distillate fuels. It was based on a test method developed by the U.S. Navy and is often used for their applications. D5304 has become more popular in recent years as the Navy and other organizations are using this method to help determine the storage stability of biofuels. Here this is accomplished by filtering the fuel through nylon membranes (again, 0.8 micron) in conjunction with a pressure filtration vessel. One of the biggest advantages of this testing method is that it allows for rapid fuel testing without requiring any additional stabilizing chemicals that could affect the integrity of the results.

For more information on fuel testing, we recommend “Fuels and Lubricants Handbook: Technology, Properties, Performance, and Testing” by George E. Totten, Steven R. Westbrook, and Rajesh J. Shah.

Browse the complete ASTM D6217 and D5304 standards

In order to keep costs down many companies perform in-house testing on the lubricating oil and hydraulic fluid in their machinery to monitor it for particulate contamination. While most facilities can’t match the detailed analysis that an oil analysis laboratory can provide, there are some commercially available kits out there that allow users to get a good idea about the quality of their industrial fluids instantly. This process is commonly known as a “patch test” and it includes the use of MCE filters to collect and isolate debris for evaluation (“patches” is a colloquial term for filters in the oil analysis industry).

The ISO recognizes the important link between contaminated oils and component life and has published a cleanliness code as well as various standard methods, such as ISO 4406:1999, that testers can reference to determine how much particulate is acceptable. For the filtration aspect, our customers often use the sterile MCE membrane filters, which are individually wrapped and are actually less expensive than their non-sterile counterparts. Pore sizes and diameters vary by user; for a pore size larger than 1.2 micron a non-sterile MCE filter should be used (non-sterile MCE filters are available up to 8.0 microns).

Clients performing this analysis can purchase the necessary components separately, but they often purchase a pre-assembled patch test kit which may include the filters, sample bottles, forceps, filter holder, a vacuum pump, and a visual correlation chart to compare the results to the approximate ISO cleanliness code. The actual components of the patch test kit, as well as the filter specifications, are likely to vary by provider so be sure to check out what is included in yours before ordering.

Consult this article from Machinery Lubrication for more information on patch testing.
Read ISO 4406:1999
Read “Decoding the ISO Cleanliness Code”

The Toxicity Characteristic Leaching Procedure as described in EPA Method 1311 is designed to determine the mobility of organic and inorganic analytes present in different forms of waste. This procedure involves extracting and filtering waste samples using specific types of glass fiber filters and extraction vessels. When following this procedure, there are two kinds of vessel that can be used to extract samples for analysis, the bottle extraction vessel and the zero-headspace extraction vessel. Which type of vessel you use depends on the volatility of the analyte being sampled. Nonvolatile analytes can be tested using a bottle extraction vessel, while the zero-headspace extraction vessel must be used when testing for the mobility of volatile analytes. Examples of volatile analytes include: acetone, benzene, methanol, toluene, and vinyl chloride.

The EPA Method specifies that the filter for both liquid and solid waste (the latter is filtered after solid phase extraction) be a 0.6 to 0.8 micron glass fiber filter. The TCLP grade filters, which are designed precisely to meet the requirements of EPA Method 1311, feature a 0.7 micron pore size and have been acid treated and rinsed with deionized water at multiple stages to handle volatile analytes. When using these filters in conjunction with a zero-headspace extraction vessel, the EPA Method dictates that the TCLP filter should have a diameter between 90 mm and 110 mm (TCLP-2 and TCLP-3 meet this specification).

For more information on the Toxicity Characteristic Leaching Procedure, consult the complete text of EPA Method 1311 here.

Steroid hormones such as estrogen are known to have profound effects on our short-term and long-term physiology, but difficulty separating them from brain tissue has long been a hindrance to further analysis. Thankfully, a new study shows scientists from the University of Massachusetts and UCLA have found success in this area by incorporating Solid-Phase Extraction (SPE) into their testing protocol.

Traditional methods of isolating steroid hormones (or “neurosteroids”) by liquid extraction are problematic because these compounds are lipid soluble and brain tissue is very rich in lipids, which turns sample preparation into a sort of scavenger hunt and can lead to inaccurate measurements. In order to solve this problem, the authors designed a two-stage protocol of liquid and solid-phase extraction, in this case using a vacuum manifold endcapped with Empore C18-SD cartridges on brain tissue samples taken from songbirds.

The authors of the paper note that since its introduction SPE has been hailed as a low-cost and safe solution to purify samples prior to immunoassay. The results of this experiment further support this claim as the researchers found the liquid/solid-phase extraction combination increased reliability and quantification of the sample measurements. They cite that the likely reason for the improvement is that SPE eliminates substances that interfere with the immunoassay’s enzyme reactions. Future tests will further examine the relationship between SPE and neurosteroids so we can improve our understanding of them.

Read the entire study here

In searching for new weapons in their fight against the destructive mountain pine beetle, scientists at the USDA Forest Service are experimenting using filtration techniques to create more effective insecticide treatment. It is estimated that 8% of forests in the United States are at risk to insect or disease outbreaks; among this percentage the mountain pine beetle is considered the biggest threat.

It’s necessary to find new solutions to protect these trees because of concerns about the future availability of one of the most commonly used insecticide chemicals, carbaryl, for environmental reasons. A study published this year examined the effectiveness of different concentrations of carbaryl along with two other known insecticides, cyantraniliprole and Cyazypyr (30 Scrabble points!).

For this experiment the researchers performed two different assays, one involved exposing the beetles to insecticide with filter paper and one through a topical treatment. For both tests they used 1 mL of various concentrations of the insecticides along with 934-AH filter paper (1.5 micron pore size, 90 mm diameter) stored in a sterile petri dish and dried in a fume hood.

In the filter paper assay, small holes were drilled into the petri dish to provide ventilation and captured beetles were placed on the filter paper. The health of the beetles was then assessed at regular intervals to determine the effectiveness of each insecticide concentration. In the topical assessment, the insecticide was applied directly onto the beetles which were then placed on top of the filter discs.

The results of the filter paper assays, which the authors believes more closely approximates field conditions than topical assays, found that is possible that much smaller amounts of carbaryl could be effective in the field, which is good news for the environment as concerns over the toxicity of this chemical have grown. As such, the authors recommend that smaller concentrations of carbaryl be tried in the field. Take that, pesky beetles!

Read the full report here

Have you ever had difficulty observing the results of microscopic work performed with polycarbonate (PCTE) or polyester (PETE) membrane filters? If so, our Cytoclear Glass Slides can help. These glass slides are frosted with a light-diffusing treatment which makes it possible to directly observe aqueous biologicals such as phytoplankton under standard (non-inverted) microscopy or to correct light refraction that can occur when analyzing bacteria on black polycarbonate filters.

For other applications where you’re looking at filters through a microscope, the cytoclear slides can help you avoid eye strain by reducing distracting lines or shadows that can occur.

Whatever your reasons for using them, you can automatically save 50% this month on cytoclear glass slides or any other membrane accessory when you order them along with any of our polycarbonate or polyester membrane filters!

You can learn more about these applications for cytoclear glass slides by reading this article on phytoplankton observation or this one on aquatic bacteria.

Here is a cool bit of news this morning; Boeing is working with Embraer and the Inter-American Development Bank to study the production of renewable jet fuel made from Brazilian sugarcane. Even sweeter is that this jet fuel is produced by one of our customers, Amyris! According to Amyris CEO John Melo the goal here is to, “help us replace fossil fuels with a renewable jet fuel that surpasses both technical and sustainability criteria.”

The study is being directed by ICONE, a non-profit Brazilian research organization, and the World Wildlife Fund is acting as an independent reviewer and advisor. Sounds like it's a dedicated coalition of minds working on this issue. We’re thrilled that we can indirectly support this kind of innovation and will look forward to seeing the results in early 2012.

You can learn more about this announcement by reading the original press release here.

If you fastidiously watch “Through the Wormhole” like I do, chances are you’ll find this application for silver membrane filters fascinating – they’re being used to assist in the collection of antimatter! Now if your main reference for antimatter is a certain Dan Brown novel, you should know that separating and collecting antimatter is a much, much more difficult process than the entertainment industry would have you believe. In fact, “If you take all the antimatter produced in the history of the world and annihilated it all at once, you wouldn't have enough energy to boil a pot of tea,” according to Harvard physicist Gerald Gabrielse. Professor Gabrielse is a leader in antimatter trapping methodology and a co-author of the paper Pumped Helium System for Cooling Positron and Electron Traps to 1.2 K, which details how our filters are used to trap antimatter.

Antimatter is composed of the exact opposite particles (particles of the same mass but opposite electrical charges) as its traditional counterpart. So whereas a hydrogen atom is made of one electron and one proton, an antihydrogen atom (called H-Bar) is comprised of a positron and an antiproton. When antimatter comes into contact with matter, even air, both particles annihilate and release energy in the form of photons (light particles) and/or radiation. Because of the extreme instability of antimatter, one of the major challenges with studying it is gathering enough of the material in a lab. To store any amount of antimatter requires an extremely powerful vacuum to prevent it from coming into any contact with matter. To this end, scientists are experimenting with all manner of “traps” in order to separate and analyze the antimatter.

It is one of these traps that pure silver membranes have found a role in the antimatter collection process. The paper referenced above explains how in order to collect antihydrogen the scientists must cool the trap apparatus to temperatures close to absolute zero. To cool the apparatus to such an extreme degree the scientists here use liquid helium (which is about -269°C), this is also where the silver filters come into play. In order to remove any impurities that could cause clogging in the apparatus, the liquid helium is twice filtered through silver filters, first through a 5 micron filter and then a 3 micron filter before continuing through the pumping system.

A popular misconception about antimatter is that it has potential as an alternative energy source. On his website Professor Gabrielse points out that “No antimatter energy source will ever be possible since it takes much more energy to make antimatter than can ever be recovered from antimatter annihilation…Our motivation for trapping antimatter is to study is basic properties and to compare them with the properties of ordinary hydrogen atoms.” So while this research isn’t going to solve our energy problems, it could help physicists answer some of the biggest mysteries regarding the makeup of the universe.

That last part would sound better coming from Morgan Freeman…

Biogas, a form of renewable energy this is produced through, among other things, animal and human waste (hey, it’s not like you were using it) is one of several developing energy sources whose proponents are exploring membrane separation techniques to improve their purification process. A recent study published in the “Applied Chemistry – A Journal of the Society of German Chemists” experimented with a new method of membrane separation called the “condensing-liquid membrane” (or CLM) in an effort to enrich raw biogas, which typically contains between 50-80% methane, to natural gas quality (at least 95% methane content), with favorable results.

Common membrane materials like Cellulose Acetate and Polyimide have been tried for this application with some success, but the problem is that they can be ruined by the aggressive gases that are present in raw biogas, such as carbon dioxide and hydrogen sulfide. The CLM is a liquid (water in this case) layer that condenses on a porous hydrophilic membrane which then gets regenerated to allow for continuous operation. This support, made from Teflon, gathers water vapor from the biogas on the feed side of the membrane and is partially removed from the permeate side by nitrogen gas, thus allowing for separation to occur in one step as the water is constantly refreshed. One of the more brilliant aspects of the CLM method is that the presence of water in biogas, usually regarded as a disadvantage, suddenly becomes a key component in the process.

Since the membranes are being preserved and not destroyed, the potential exists for this process to be a cost-efficient method of purifying biogas in the future. Researchers will continue to investigate the CLM method in order to find the optimal conditions that will make it even more efficient.

Visit here to read the full report “Effective Purification of Biogas by a Condensing-Liquid Membrane.”

To learn more about biogas, try this site from Alternative Fuels and Advanced Vehicles Data Center and the U.S. Dept. of Energy.

How does a biogas plant work? Watch this animated video to get an idea.

Cruising around the Scandinavian coastline in November might not sound like the most ideal place to conduct an environmental impact study, but for Norway’s Institute of Marine Research it was necessary in order to investigate the levels of anthropogenic particles in the Skagerrak strait. As you can imagine, this setting presented some unique challenges for the research team. In order to gather and analyze microscopic samples from this body of water, which is located between Norway, Denmark and Sweden, researchers had to come up with some new sampling methods and fashion their own equipment to solve problems that had plagued previous studies.

Norwegian Researchers Hard at Work^

One key obstacle that these scientists needed to overcome was how to distinguish between anthropogenic particles, which are man-made bits of matter that impact the environment (i.e. oil-spill droplets, asphalt, rubber tire wear, fly ash), from those particles with similar characteristics which appear naturally (volcanic ash, peat). To make this distinction, the samples were subjected to morphology analysis of their color and texture to first determine their origin before being counted.

The second major challenge was how to prevent contamination, which is easier said than done considering the harsh and unpredictable nature of the sea. One of the steps the researchers took to solve this was to develop control samples, free of any contaminants, which they could actually bring on board the ship with them. To further reduce the potential of contaminating samples, they also created new methodology and constructed their own customized sampling apparatus.

You can see a schematic of the sampling equipment the Institute researchers built in their published study. Their setup involved a submersible water pump that was positioned inside a waterproof case connected to the sampling filter (10 μm hydrophobic polycarbonate membrane filters, along with a 30 μm square mesh nylon filter as a support) which was placed directly in the sea. To protect the filter from wave turbulence they modified one of our filter holders (this one) with a new outlet fitting and a larger, semi-enclosed inlet with a smooth surface. The filters were also placed in protective holders before and after filtration for protection and to reduce the risk of contamination. As an added protective measure, the filter apparatus was ultrasonically cleaned prior to use. The entire sampling apparatus was held 2 meters outside the boat (to further prevent contamination) and the sampling depth was limited to between 0.1 and 1.5 meters to protect it from large waves.

While it will take many more studies before conclusions can be drawn about the state of this particular body of water, the scientists were encouraged by the results of the new methodology they created. They note in the conclusion how these improvements have standardized the sampling and reduced the risk of contamination. The scientists also suggest that this sampling equipment could be adapted for larger particles.

To read the full study, visit here.
^Image from Survey of microscopic anthropogenic particles in Skagerrak. Lysekil and Flødevigen 2010-11-20, Institute of Marine Research.