Fistreem Glossary
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B
Bacteria
A large group of single cells microorganism. Bacteria are classified into five groups according to their basic shapes; spherical (cocci), rod (bacilli), spiral (spirilla), comma (vibrios) or cockscrew (spirochetes). They can exist as single cells, in pairs, chains or clusters.
C
CFU/ml
Colony Forming Units per millilitre is a measure of viable microbial populations.
Colloidal Particles
Colloids contain iron, aluminium, silica and organics are commonly found in natural potable waters. A stable dispersion of fine particles that are typically less than 0.1µm.
Conductivity
The conductivity of a solution is a measure of its ability to conduct electricity. Conductivity is expressed in microsiemens/cm (µS/cm). The ability of water to conduct an electric current is directly related to the amount of ionic material (salts) dissolved in the water.
D
Deionisation
Deionisation involves the removal of impurity ions from water. Ion-exchange resins are used to chemically remove ions from feed water. As water passes through the ion exchange resin beads, hydrogen and hydroxide ions are chemically exchanged with dissolved minerals to form water.
Dissolved Gases
Water contains naturally dissolved carbon dioxide, nitrogen and oxygen. Dissolved gases can alter the pH of laboratory water and can change the ionic balance. High levels of dissolved oxygen and nitrogen can result in bubble formation, which can hamper the flow through chromatography columns and micro-channels. Dissolved carbon dioxide will raise the acidity of water and reduce the capacity of ion exchange resins in Deionisation systems.
Distillation
Distillation is a long-established method that separates water from contaminants by changing the state of water from a liquid phase to a gas phase and then back to a liquid phase.
E
Endotoxin
Endotoxins are the main component of the outer membrane of gram-negative bacteria. They contribute to the structural integrity of bacteria. Endotoxins can also act like pyrogen.
F
Filtration
Is the purification process in which the passage of fluid through a porous material result in the removal of impurities.
H
High Performance Liquid Chromatography (HPLC)
Is an analytical technique to separate, identify, and quantify components in a mixture.
I
Inorganic Ions
Inorganic ions include silicates, chlorides, calcium, magnesium, phosphates, fluorides, bicarbonates, sulphates, nitrates and ferrous compounds. High quantities of ions will increase conductivity and reduce resistivity.
M
Microorganisms
A microscopic organism, especially a bacterium, virus, or fungus. Bacteria and fungi interfere with sterile research applications. Free-floating bacteria can form a biofilm on the surfaces, which can be difficult to remove.
N
Nucleases
Enzymes (RNase and DNase) cleave the chains of nucleotides in nucleic acid into smaller units.
O
Organic Compounds
Organic compounds are molecules that are made up of carbon covalently bonded to other atoms, e.g. hydrogen, oxygen and nitrogen.
P
pH
It is a measure of the relative amount of free hydrogen and hydroxyl ions in the solution. The range goes from 0-14, with 7 being neutral. pHs less than 7 indicate an acidic solution, whereas a pH value above 7 indicates a base.
PPB (Parts Per Billion)
It is a unit equal to a microgram per kilogram of water. Numerically ppb is equivalent to microgram per litre in dilute aqueous solutions.
Pyrogens
Pyrogens are typically endotoxins derived from Gram-negative bacteria walls.
R
Resistivity
Resistivity is a measure of the resisting power of a specified material to the flow of an electric current. Resistivity is usually reported in megaohm-centimetres (MΩ-cm) at 25°C.
Reverse Osmosis
A process in which water is forced under pressure through a semipermeable membrane leaving behind dissolved organic, dissolved ionic and suspended impurities.
S
Suspended Particles
Large, suspended particles such as sand, silt, clay or vegetation between 1 and 10µm can cause turbidity in water.
T
Total Organic Carbon (TOC)
Is the total concentration of carbon present in organic compounds.
U
Ultra-Pure Water
Ultra-pure water refers to ASTM (American Society for testing and Materials), which states water quality with a resistivity of 18.2MΩ-cm at 25°C. Ultra-pure water is used for highly sensitive procedures like HPLC, AAS and mammalian cell culture.
Ultra-Violet (UV)
UV is used to disinfect water. Two wavelengths are commonly used 185nm and 254nm.
Ultrafiltration
A process in which water is filtered through a selectively permeable membrane having a very fine pore structure to remove pryogens and nucleases.
V
Viruses
A virus is an infectious microbe consisting of a segment of nucleic acid (either DNA or RNA) surrounded by a protein coat.
