Membrane Capacitive Deionization in work



Deionized water (DI) is deeply demineralized, ultra-pure water with the resistivity close to 18 megohm-cm. It is used in microelectronics, printed circuit boards, instrument manufacture, pharmacy, washing liquids, etc.

In order to obtain the high quality pure deionized water, a multi-stage water purification process can be used. After pre-cleaning, the water is supplied to the reverse osmosis membrane, and then the water is filtered through a special deionization medium, which removes the rest of the ions in the water. The purity of deionized water can exceed the purity of distilled water. [1]

Deionization removes minerals and ions, both cations (positively charged ions) and anions (negatively charged ions), through a chemical process. DI uses specially manufactured ion-exchange resins which exchange hydrogen ions and hydroxide ions for dissolved minerals, which are then recombined to form water (this leaves DI in an unbalanced condition and with an electrical charge.) DI does not significantly remove uncharged organic molecules, viruses or bacteria. Because deionized water is unbalanced, it goes after any dissolvable or absorbable ions on contact trying to return to a balanced state.

Clinical Use[]

Deionized water is used when an application requires a soft solvent. DI water works best in cooling applications because of its lack of mineral deposits. Deionized water is also used in reagent preparation, transferring an analyte within a test procedure, as a calibration standard or analytical blank. [2] Different types of blanks are used to identify the source of contamination in the sample. The types of blanks include equipment blank, field blank, trip blank, method blank, and instrument blank, and for cleaning lab equipment. DI water is best for washing glassware because of the absence of minerals and ions. DI is corrosive and should not be used when there will be extensive contact with certain metals. [3] The IDA-4 Plus Infusion Device Analyzer is intended for use with de-ionized water since tap water may contain contaminates which will also damage the transducer. [4] However, the Rigel Multi-Flo Infusion Pump Analyzer is intended for use with distilled water.[5]

Deionized water should never be consumed as drinking water since the deionized process does not remove bacteria or viruses (compared to municipally filtered drinking water.)


  1. Distilled and Deionized Water. "Deionized Water vs Distilled Water: What’s the Difference." Accesssdate 1/13/2015.
  2. EPA. Quality Control Tools: Blanks. Accessdate 2013-05-30.
  3. BTS. "Distilled or Deionized Water? What’s the Difference?" Accessdate 1/13/2015.
  4. Fluke Biomedical. IDA User Manual. April 2005. pg. 3-4.
  5. Rigel Medical. Multi-Flo User Manual. 2014. pg. 14.




Distilled versus Deionized Water