What type of water is considered the purest form?

Type I water is considered the purest form of water commonly used in laboratory settings. It undergoes extensive purification processes to remove impurities, which may include contaminants like ions, organic molecules, and microorganisms. This level of purity is essential for applications in molecular biology, high-performance liquid chromatography (HPLC), and various analytical procedures, where even trace amounts of impurities can affect experimental results.

Type I water typically has a resistivity of 18.2 MΩ·cm at 25°C and is devoid of any detectable levels of contaminants. This makes it suitable for use in high-stakes experiments and preparations where precision and reliability are paramount.

In contrast, Type II and Type III water have progressively more impurities and are used for less critical applications, such as general laboratory work or washing glassware. Type IV is the least purified and may contain higher levels of salts and other substance concentrations, suitable for routine purposes but not for sensitive experiments. Thus, Type I's extensive purification process is what establishes it as the standard for the purest laboratory water.