According to the "Specifications and Test Methods for Water Used in Analytical Laboratories" (GB6682-2008), pure water in analytical laboratories is divided into three levels: primary water, secondary water, and tertiary water.

Primary water is used for preparing standard water samples or analyzing ultra trace amounts of substances. Primary water does not contain dissolved impurities or colloidal organic matter, and can be further processed to obtain secondary water.

For example, secondary water can be distilled through quartz equipment or treated with an ion exchange mixed bed, and then produced through a 0.2 micron microporous filter membrane.

Secondary water is used for analysis and research work.

Secondary water often contains trace amounts of inorganic, organic, or colloidal impurities and can be prepared by multiple distillation or ion exchange methods.

The raw material for laboratory pure water should be drinking water or relatively clean water. If there is pollution or the blank cannot meet the requirements, purification treatment must be carried out.