Ultra Pure Water vs. Deionized Water
Ultrapure water (UPW), formulated as H2O, contains no contaminants. Such water is the most appropriate for laboratory requirements where you need water with certain biological, elemental and organic level specifications.
On the other hand, deionized water is produced by the process of distillation by a single or double glass device or quartz distillation system, or purified by Ion exchangers to make the water free from ions. This deionized quality of water has no assurance on the contaminant levels unlike in the case of ultrapure water, where the purity is 100%. Since deionization as a technology is just an ion exchange-based purification method to purify water, theoretically it has very limited control on other contaminants like organic, biological or most elemental contaminants. Though deionization technology can remove ionic contaminants and any compound which has charges, it has no removal specifications for organic/biological contaminants to ensure that the water is free of all contaminants.
Broadly, if we compare the deionized water and Ultrapure Water, UPW is much more acceptable due to its stringent quality specifications. On the other hand, deionized water with its limitation on removal of major contaminants is only preferred by few end users.
Cost is another major deciding factor for end users to choose one above another. Since ultrapure water has high quality and consistency, the end user shouldn’t hesitate to pay extra. The technologies used are — series of ion exchangers for deionization to control ionic contaminants, activated carbon for control on organic elements, UV for control on biological and organic contaminants, depth and screen filter for keeping particles and biological contents down with their cutoffs sizes. On the other hand, in Deionization technology, you have only combination of ion exchangers which controls only the ionic contamination, that may be economical to the end user.
This information is very vital when we choose the purification technology for our applications. For example, if a scientist has operational laboratory having the combination of applications like HPLC, LCMS, ICPMS, molecular biology and ion chromatography which needs water free of all the contaminants viz ions, organic, elements etc., he cannot completely rely on deionized water. A scientist who has non-sensitive applications and is not working at nanogram or sub nanogram level, can take the option of deionized water for his application uses without obstructing the application or analysis.
Overall, it’s a matter of water quality requirements we need to consider for our laboratory applications and this must be chosen carefully.
