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F.A.Q. Water Purification


Speaking the Language of Lab Water

To make pure and ultrapure water, the impurities must be efficiently and effectively removed. Barnstead water purification systems employ multiple technologies, some synergistically, to remove impurities and give you consistently PURE water. Water purification is a step-by-step process often requiring a combination of technologies, each of which varies in the ability to remove specific contaminants.

The table below illustrates which impurities are removed by each technology.

Impurities removed by multiple technologies

Common Water Impurities

Don't let impurities contaminate your sensitive experiments. Thermo Scientific Barnstead water purification systems are engineered to remove impurities that threaten your research so you can focus on what's important – your next discovery.

Suspended Particles

Sand, silt, clay and other suspended particles cause water to be turbid. These suspended particles can interfere with instrument operation, plug valves and other narrow flow paths, and foul reverse osmosis membranes. They typically range from 1 – 10 μm in size.


Colloidal particles typically have a slightly net negative charge, range in size from 0.01 – 1.0 μm, and can be either organic or inorganic. Unlike suspended particles, colloids do not settle out by gravity, but remain suspended in the liquid that carries them. Colloids clog filters, interfere with instrument operation, foul reverse osmosis membranes and can bypass ion exchange resins, resulting in lower resistivity in deionized water systems.

Inorganic Ions

Impurities such as silicates, chlorides, fluorides, bicarbonates, sulfates, phosphates, nitrates and ferrous compounds are present as cations (positively charge ions) and anions
(negatively charged ions). Water with a high concentration of ions will conduct electricity readily and have high conductivity and low resistivity, as conductivity and resistivity are inversely related. Ions will adversely affect the results of inorganic analyses such as IC, AA, ICP/MS and may retard cell and tissue growth in biological research. They can also affect the cartridge life in deionized water systems

Dissolved Organics

Organic solids are present from plant and animal decay and from human activity. They may include proteins, alcohols, chloramines and residues of pesticides, herbicides and
detergents. They foul ion exchange resins, interfere with organic analyses including HPLC, gas chromatography and fluoroscopy. They will also hinder electrophoresis, tissue
and cell culture.

Dissolved Gases

Water naturally contains dissolved gases such as carbon dioxide, nitrogen and oxygen. Carbon dioxide dissolves in water to form weakly acidic carbonic acid (H2CO3), which
can alter the pH of the water. Additionally, oxygen, the most common non-ionized gas, may cause corrosion of metal surfaces.


Bacteria, fungi and algae are found in all natural water sources. Chlorination eliminates harmful bacteria, but tap water still contains live microorganisms which interfere with sterile applications, such as cell and tissue culture.

Pyrogens and Viruses

Pyrogens or bacterial endotoxins are lipopolysaccharide molecules incorporated in the cell membrane of gram negative bacteria. Viruses are considered to be non-living nucleic acids. Both can adversely affect laboratory experiments often hindering cell and tissue growth in culture.


RNase and DNase are naturally occurring enzymes that are instrumental in regulating bodily functions. As important as these enzymes are to the life process, they can be devastating to nucleic acid experiments. If these contaminants are present in the lab water used, the ability to amplify DNA molecules will be severely limited. Likewise, experiments utilizing RNA can be ruined.


Distillation has the broadest removal capabilities of any single form of water purification.

Water is boiled and undergoes phase changes during the distillation process, changing from liquid to vapor and back to liquid. It is the change from liquid to vapor that separates the water (in various degrees) from many dissolved impurities, such as ions, organic contaminants with low boiling points < 100°C , bacteria, pyrogens and particulates. Distillation can not be used on its own to remove inorganic ions, ionized gases, organics with boiling points higher than 100°C , or dissolved non-ionized gases.

Distillation Diagram



Systems that utilize this technology

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