Bench-top water purification systems can deliver bacteria-free water and more

By Bob Applequist, Senior Application Specialist

On December 11, 2014 in Articles

Microbiology and molecular biology laboratories require highly purified water, often called Type I or 18 megohm water. This pure water must be bacteria-free as well as endotoxin-free. Endotoxins, the fragments of gram-negative bacteria cell walls, can cause negative effects on cell cultures. Additionally, many molecular biology labs studying RNA and DNA require the reduction of nucleases (RNase and DNase) which are very common contaminants resulting from destruction of bacterial nucleic acids.

Bench-top water purification systems employ several purification steps to produce bacteria-free, endotoxin-free, and RNase/DNase-free water. These technologies include carbon adsorption, ion exchange, UV oxidation and ultrafiltration.

Using 0.2 micron filters can remove bacteria; however, ultrafilters must be used to remove endotoxins and nucleases. Ultrafilters are rated by their dalton molecular weight cut-off or lowest molecular weight filtration point.

Daltons are a unit of molecular mass; one dalton is approximately equal to the mass of a hydrogen atom. The dalton unit is used to define the size of an organic compound. Organic compounds can range from a simple molecule, CH₄, to complex molecules such as proteins and nucleases weighing more than 13,000 daltons. With a cut-off point of 13,000 daltons, the WaterPro BT Ultrafilter will remove these complex molecules.

A disposable Ultrafiltration Cartridge offers an economical solution for scientists who need ultrapure water for cell culture, biochemistry or molecular biology applications. The cartridge is installed at the outlet of most bench-top water purification system and produces pyrogen-free, nuclease-free, ultrapure water for a period of up to three months.

The Acrylonitrile Butadiene Styrene (ABS) cartridge contains polysulfone hollow fibers. The Ultrafiltration Cartridge maintains a high flow rate and minimizes the release of ionic and organic materials.

To ensure you select the right water purification system for your application, many questions need to be answered. Contact a water purification expert for help selecting the appropriate system.