Ultrapure water

Detailed article on ultrapure water for medical students

Ultrapure Water

A droplet of ultrapure water, free from impurities.

Ultrapure water (UPW) is water that has been purified to the highest standards of purity, containing no detectable impurities. It is used extensively in the semiconductor industry, pharmaceutical manufacturing, and laboratory settings where the presence of contaminants could interfere with sensitive processes or experiments.

Characteristics

Ultrapure water is characterized by its extremely low levels of contaminants, including ions, organic compounds, particulates, and microorganisms. The purity of ultrapure water is often measured in terms of its resistivity, which approaches 18.2 megohm-cm at 25°C, indicating the absence of ionic impurities.

Ionic Contaminants

Ionic contaminants in water can include cations such as sodium, calcium, and potassium, as well as anions like chloride, sulfate, and nitrate. In ultrapure water, these ions are removed to levels below 1 part per billion (ppb).

Organic Contaminants

Organic contaminants are removed to levels below 1 part per trillion (ppt). These include volatile organic compounds (VOCs) and non-volatile organic compounds (NVOCs) that can interfere with sensitive analytical techniques.

Particulates

Particulates are solid particles that can be present in water. In ultrapure water, the concentration of particulates is minimized to prevent interference with processes such as photolithography in semiconductor manufacturing.

Microorganisms

Microorganisms, including bacteria and viruses, are removed from ultrapure water to prevent contamination of sensitive processes. This is achieved through filtration and sterilization techniques.

Production

The production of ultrapure water involves multiple stages of purification, including:

• Pre-treatment: Removal of large particulates and organic matter using filters and activated carbon.
• Reverse osmosis: A membrane process that removes dissolved ions and organic molecules.
• Deionization: Using ion exchange resins to remove remaining ionic contaminants.
• Ultrafiltration: Removal of particulates and microorganisms.
• UV oxidation: Degradation of organic contaminants using ultraviolet light.
• Final filtration: Removal of any remaining particulates and microorganisms.

Applications

Ultrapure water is essential in various industries and research fields:

• In the semiconductor industry, it is used for rinsing silicon wafers to prevent contamination that could affect the performance of electronic devices.
• In pharmaceutical manufacturing, ultrapure water is used in the production of injectable drugs and other products where contamination could pose a health risk.
• In analytical chemistry, ultrapure water is used as a solvent and in the preparation of reagents to ensure accurate results.

Related Pages

• Water purification
• Semiconductor manufacturing
• Pharmaceutical industry
• Analytical chemistry