4.1 The purity of water is relative and is usually characterized by the limits of impurities found in the water as well as by the methods used to prepare and handle the water. Section 7 mentions the suitable methods for water preparation.

1.1 This guide is intended to describe the chemical and biological characteristics of water to be used whenever critical purity is essential to the use intended in laboratory Bio-Applications, for example, clinical, pharmaceutical, and biomedical. The importance of such a reagent is often underestimated despite the impact that it can have.

1.2 This guide is not intended to be used as a reference in preparing water for injectables. Generally, the appropriate use of this guide may include experiments involving tissue culture, chromatography, mass spectrometry, Polymerase Chain Reaction (PCR), DeoxyriboNucleic Acid (DNA) sequencing, DNA hybridization, electrophoresis, molecular biology or analyses where molecular concentrations of impurities may be important.

1.3 For all the other applications linked to an ASTM method and not bio-sensitive that require purified water, it is recommended that Specification D1193 or Test Method D5127 be consulted.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.