All You Need to Know About Deionized Water

What is deionized water?

Deionized Water, or DI water for short, is pure water that has been specially treated to remove almost all soluble ions from the water. Ions in water usually come from nature, such as calcium, magnesium, sodium and other metal ions that are absorbed when water flows through the soil, and iron, copper and other metal elements that may be dissolved during piping. These ions are widely present in ordinary tap water and are the main source of water’s electrical conductivity and chemical reactivity. By using ion exchange resins or other deionization techniques, these cations and anions can be effectively removed, resulting in high purity, low conductivity water. Deionized water is commonly used in laboratories, biotechnology, electronics manufacturing and other areas where water quality is critical, and is an indispensable base solvent for many high-precision applications.

Deionized water vs. distilled water

Although deionized water and distilled water are both pure water, they differ in the way they are purified and the types of impurities they remove. Deionized water removes charged contaminants from water, especially mineral ions such as sodium, calcium, and magnesium, primarily through an ion exchange process. Distilled water, on the other hand, is obtained by heating water and condensing the steam to obtain pure water. This process not only removes mineral ions, but also effectively removes a variety of charged or uncharged contaminants, including certain organics and microorganisms. Therefore, in comparison, distilled water is more advantageous in removing non-ionic impurities, while deionized water is more prominent in efficiently removing dissolved inorganic ions.

How is deionized water produced?

Deionization of water can be achieved by a variety of methods. The deionization and purification technologies we use include:

Electrodeionization (EDI)
EDI is a water treatment technology that uses an electric current, ion exchange membranes and resins to remove ions and other ionized substances, such as salts and organic acids, from water. An electrolysis tank contains ion exchange resins separated by ion exchange membranes. When water flows through, an electric current pushes the ions through these membranes and resins, thereby purifying the water.
Ion Exchange (IX)
Ion exchange is a deionization process in which water is passed through a bed of ion exchange beads. When water comes into contact with these beads, ions are transferred from the water to the beads. They are then replaced by hydrogen and hydroxyl ions in the water. The end result is pure water.
Reverse Osmosis (RO) Deionization
Reverse osmosis (RO) deionizes water. The RO process involves passing water through a semi-permeable membrane to remove impurities from the water, including ions, organic compounds, and particulate matter. RO-treated water is ultimately purified to the level of pure water. Combined with the deionization process, this ensures a high level of water purity.

What is deionized water used for?

Deionized water is extremely valuable because of its high purity. Ions usually carry an electrical charge. Deionization of water removes these charges. As a result, it is used in a wide variety of industries for a wide range of purposes.

Laboratory Applications
Deionized water is an excellent instrument cleaning water and is widely used in daily laboratory operations. Due to its high purity characteristics, deionized water can effectively adsorb impurities and contaminants on the surface of equipment, enhancing the cleaning effect. Deionized water does not contain minerals or other soluble impurities, so it does not leave any residue on the surface of the instrument after cleaning. It ensures that the equipment is clean and free from pollution, especially suitable for precision experimental environments with high requirements for cleanliness.
Clinical Biochemistry
In biochemistry experiments, residual ions in water may interfere with the reaction process, affecting the accuracy of experimental results and the reliability of immunoassay. The use of deionized water can effectively avoid these interfering factors and provide more stable and accurate data support for clinical biochemistry analysis.
Electrochemistry
Due to its extremely low conductivity, deionized water is often used in electrochemical experiments to avoid impurity ions in the water interfering with the measurement of electrical signals. In addition, if the incoming water contains un-removed ions, it may react with specific ions introduced in the experiment, leading to changes in electrical properties, thus affecting the accuracy and reproducibility of the experimental results.
Cell Tissue Culture
When performing cell cultures, the number of ionic species in the culture system should be minimized, as certain ions may have toxic effects on specific types of cells. Such ionic contamination may not only inhibit cell growth or induce abnormal reactions, but also affect the reliability and accuracy of experimental results.
Immunochemistry
Maintaining a stable pH is critical in immunochemistry experiments. The presence of ions in water can upset this balance, especially metal ions, and may also interfere with detection processes such as fluorescence or absorption. The use of deionized water helps to avoid these interferences and ensures the stability and accuracy of experimental data.
Molecular Biology
Deionized water is ideal for use in molecular biology experiments. Negatively charged impurity molecules may mimic the charge characteristics of DNA, thereby interfering with relevant enzymatic reactions. In electrophoresis experiments, the presence of excess ions in water can affect the overall ion concentration, which in turn disrupts the pH balance and the ionic strength of the buffer, leading to unstable separations or distorted data. The use of deionized water can effectively avoid these problems and improve the accuracy and reproducibility of the experiment.
Mass Spectrometry
In mass spectrometry, it is critical to use high purity water to avoid any impurities that may interfere with the process or results. Deionized water is an extremely effective choice for such applications.
Spectrophotometry
Spectrophotometry utilizes the amount of light absorbed by a solution to measure the amount of a substance. Ions absorb light, which can affect the results. In these applications, the use of deionized water avoids this interference.