Page 66 - Blog

Have you ever wondered where you would be without Thomas Graham? If you are a chemist or membrane scientist, you probably should. Scientists of many disciplines are indebted to Thomas Graham for his groundbreaking studies on gas flow through microporous membranes. His work, which included creating Graham’s Laws of Diffusion to describe the relative permeation rate of two gases, was instrumental in the creation of colloidal chemistry and the advancement of membrane science. In terms of real world applications, Graham’s efforts are a precursor to inventions ranging from the artificial kidney to the atomic bomb. His feats are even more impressive when you consider that in order to perform his experiments he had to first generate the necessary gases himself, and also that his selection of membrane materials was limited to whatever objects he could find, such as rubber balloons, animal bladders, and thin metal sheets. Thomas Graham was born in Edinburgh, Scotland in 1805 and enrolled in the

When counting bacteria as part of epifluorescent microscopy we generally recommend using the black polycarbonate membranes instead of cellulose membranes. This is because the black polycarbonate materials have a uniform pore size and flat surface that will retain all of the bacteria without trapping any inside of the filter. Though cellulose membranes will retain bacteria, it often will become trapped inside of the filter, where it cannot be counted.

Is nothing sacred? In the news today came word that the period table is changing the atomic weights of 10 elements. Instead of being listed as one static value, the atomic weight for these elements will now be displayed as a a range that will more accurately reflect how the elements actually appear in nature. The change is being made after decades of study and this is the first time in the history of the periodic table that any atomic weights will be altered. Measuring the variance of atomic weights is being used in real world applications for everything from analyzing food purity, to determining which athletes are using performance enhancing drugs! The elements being changed are: Boron, carbon, chlorine, hydrogen, lithium, nitrogen, oxygen, silicon, sulfur, and thallium.

Recently one of our customers was interested in testing Legionella bacteria and asked us how our polycarbonate membranes fit into the process mentioned on our website. If you are unfamiliar with Legionella, it is a waterborne pathogen commonly found in aerosolized waters such as cooling towers, showers, and humidifiers, and it is best known as the cause of Legionnaire’s Disease as well as Pontiac Fever. Its name originated from an outbreak that occurred at the 1976 convention of the American Legion in Philadelphia.

There are actually two areas in which membranes are used in regards to Legionella: Sample preparation and point-of-use filtration. For sample preparation the CDC (Centers for Disease Control) recommends using a 0.2 micron, 47mm polycarbonate filter to extract Legionella bacterium from potable water. Non potable water utilizes a direct plating procedure.

Point of use filtration frequently involves a device that attaches to a faucet or showerhead to eliminate Legionella. Such devices