The Difference Between Grade I, Grade II, And Grade III Water in the Laboratory

In experiments, you often hear about Grade I, Grade II, and Grade III water, but do you know which type of water to use in your experiment?

I. Specifications (GB/T6682-2008)

Grade I water has the highest purity, containing almost no ions, organic matter, or microorganisms; Grade III water has the lowest purity, meeting only basic experimental needs.

II. Preparation Methods

Grade I Water: Requires further treatment by Grade II water, commonly prepared using an ultrapure water system (reverse osmosis + ion exchange + UV oxidation). It is generally prepared and used immediately or stored in a dedicated sealed container to avoid contamination.

Grade II Water: Prepared through multiple reverse osmosis or multi-effect distillation processes. It can be stored for short periods in clean containers.

Grade III Water: Used as raw material from tap water, requiring simple treatment such as distillation, ion exchange, or reverse osmosis.

III. Applicable Scenarios

Grade I Water: Used for high-precision experiments, such as high-performance liquid chromatography (HPLC), atomic absorption spectrometry, cell culture, and molecular biology experiments (e.g., PCR), where absolutely no impurities are required.

Grade II Water: Suitable for general analytical experiments, such as spectrophotometric detection, titration analysis, reagent preparation (non-trace analysis), and cleaning of laboratory equipment. Grade III water: Primarily used for basic operations, such as preliminary cleaning of glassware, replenishing water baths, routine chemical reactions (without strict purity requirements), and preparing non-analytical solutions.

In summary, laboratory water selection should be based on the required experimental precision: Grade I water for high-precision experiments, Grade II water for routine analysis, and Grade III water for basic operations.