Deionized Water:
Clinical and school laboratories often rely on pure water for most tests in the laboratory rather than relying on tap water. For this reason, most places will have a water deionizing system that produces analytical-grade, or type 2 water, free from impurities, organic materials, and bacteria. Most of these systems rely on osmosis, or reverse osmosis (RO) techniques, which utilize a carbon or charcoal-based filter, a thin, semipermeable membrane, designed to remove impurities found in tap water, including calcium, magnesium, sodium, chloride, sulfate, bicarbonate, and free chlorine, as well as remove bacteria and silica.
Water deionizing systems are based upon resistivity and conductivity. These systems contain resistivity and conductivity meters, which monitor the purity of ionic water and measure the ability of the water to resist or conduct an electric current, which is directly related to the amount of ionic material (salts) dissolved in the water. Organic material is referred to as "total dissolved solids", or TDS.
In absolute pure water, resistivity will be greater than 5-15 million ohms x cm at 25 degrees Celsius. Conductivity will be <0.2 microsiemens/cm. System recovery of pure water is only about 15%, unless it is a huge company with a super high pressure pump, and the rest is lost as waste water containing impurities. A high level of TDS results in low resistivity and high conductivity. A low level of TDS results in high resistivity and low conductivity. This depends upon temperature as well, and any increases in temperature will result in an increase of conductivity.
The specific resistance is corrected to 25 degrees Celsius, or R-25, between 2, 1 cm square plates spaced about 1 cm apart and measured at 25 degrees Celsius. The space between the 2 plates is a 1 cm cube. This is known as a probe, which may vary somewhat in size and shape. A coded multiplier is included to compensate for these differences in size and shape, and it is referred to as a "cell constant". Most deionizers measure temperature, along with resistivity and conductivity.
The resistance of absolute pure water is 18.2 (rounded) million ohms x cm at 25 degrees Celsius, and conductivity is 0.055 microsiemens/cm measured inline. This is a closed system, which is important because it means that no energy is wasted and the system is efficient. This prevents atmospheric interference of CO2. CO2 is absorbed into the solution, reacting with water, and forming carbonic acid. Carbonic acid in solution disassociates to form counter ions, which conduct an electric current. Ohms are units of electric resistance, whereas siemens, or mho's, are units of electric conductivity.
Enclosed filters utilize reverse osmosis (RO) technique and a high pressure pump to remove ions and free chlorine from water, which then pressurizes by the pump and is purified by reverse osmosis as it goes through electrodeionization (EDI) module. This decreases levels of organic and mineral contaminants, ions, and bacteria.
Some hospitals use the Millipore system, which is a TOC analyzer and uses ion chromatography to reduce impurities in the water to <30 ppb (parts per billion). The specific resistivity of water can fall below below 8-10 million ohms x cm at 25 degrees Celsius in less than a minute while refilling. It is a closed system which uses thin, semipermeable filters and reverse osmosis (RO) to remove ions from the water to create analytical-grade, type 2 water for clinical analyzers. It also utilizes UV photo-oxidation to kill bacteria that might be present in the water. One of the filters contains synthetic activated carbon, where organic materials are adsorbed onto the filter to provide ultrapure water.
Water deionizing systems are based upon resistivity and conductivity. These systems contain resistivity and conductivity meters, which monitor the purity of ionic water and measure the ability of the water to resist or conduct an electric current, which is directly related to the amount of ionic material (salts) dissolved in the water. Organic material is referred to as "total dissolved solids", or TDS.
In absolute pure water, resistivity will be greater than 5-15 million ohms x cm at 25 degrees Celsius. Conductivity will be <0.2 microsiemens/cm. System recovery of pure water is only about 15%, unless it is a huge company with a super high pressure pump, and the rest is lost as waste water containing impurities. A high level of TDS results in low resistivity and high conductivity. A low level of TDS results in high resistivity and low conductivity. This depends upon temperature as well, and any increases in temperature will result in an increase of conductivity.
The specific resistance is corrected to 25 degrees Celsius, or R-25, between 2, 1 cm square plates spaced about 1 cm apart and measured at 25 degrees Celsius. The space between the 2 plates is a 1 cm cube. This is known as a probe, which may vary somewhat in size and shape. A coded multiplier is included to compensate for these differences in size and shape, and it is referred to as a "cell constant". Most deionizers measure temperature, along with resistivity and conductivity.
The resistance of absolute pure water is 18.2 (rounded) million ohms x cm at 25 degrees Celsius, and conductivity is 0.055 microsiemens/cm measured inline. This is a closed system, which is important because it means that no energy is wasted and the system is efficient. This prevents atmospheric interference of CO2. CO2 is absorbed into the solution, reacting with water, and forming carbonic acid. Carbonic acid in solution disassociates to form counter ions, which conduct an electric current. Ohms are units of electric resistance, whereas siemens, or mho's, are units of electric conductivity.
Enclosed filters utilize reverse osmosis (RO) technique and a high pressure pump to remove ions and free chlorine from water, which then pressurizes by the pump and is purified by reverse osmosis as it goes through electrodeionization (EDI) module. This decreases levels of organic and mineral contaminants, ions, and bacteria.
Some hospitals use the Millipore system, which is a TOC analyzer and uses ion chromatography to reduce impurities in the water to <30 ppb (parts per billion). The specific resistivity of water can fall below below 8-10 million ohms x cm at 25 degrees Celsius in less than a minute while refilling. It is a closed system which uses thin, semipermeable filters and reverse osmosis (RO) to remove ions from the water to create analytical-grade, type 2 water for clinical analyzers. It also utilizes UV photo-oxidation to kill bacteria that might be present in the water. One of the filters contains synthetic activated carbon, where organic materials are adsorbed onto the filter to provide ultrapure water.