A Deep Understanding of the Essential Ultrapure Water System in the Laboratory

With the advancement of science and technology, people's understanding of various things in nature is developing towards a microscopic and essential direction. Many experiments and tests require impurities in reagents or culture environments to reach ppb level, and some even reach ppt level. For example, in life science research, there is great sensitivity to various pollutants in water, especially heavy metals and soluble organic matter.

Pure Water Main Uses:

● Final cleaning of laboratory glassware

● Water for preparing buffer solutions and chemical reagents

● Water for preparing microbial culture media

● Pure water for hydrogen generators, indoor humidifiers, and autoclaves

● Drinking water for humans or laboratory animals, etc.

Ultrapure Water Main Uses:

● Water for animal and plant cell culture

● Water for various medical biochemical analyzers, analytical instruments, and hemodialysis machines

● Water for preparing and diluting analytical reagents and drugs

● Water for physiological, pathological, and toxicological experiments

● Purified and high-purity water for hospitals, pharmaceutical preparation rooms, and central laboratories

● Water for atomic absorption spectrometry

● Water for in vitro fertilization

● Water for various high-performance liquid chromatography and ion chromatography

● Other various laboratory and pharmaceutical water uses. 

Main Processes of Ultrapure Water Purification

Common impurities in natural water include soluble inorganic matter, organic matter, particulate matter, microorganisms, and soluble gases. Ultrapure water systems aim to remove these impurities as thoroughly as possible.

Currently, commonly used water purification methods include distillation, reverse osmosis, ion exchange, filtration, adsorption, and ultraviolet oxidation. Ultrapure water systems generally divide the water purification process into four main steps: pretreatment (primary purification), reverse osmosis (producing pure water), ion exchange (producing 18.2 MΩ·cm ultrapure water), and final treatment (producing ultrapure water meeting specific requirements).

Pretreatment

Since the pretreated water will undergo further purification via reverse osmosis, it is crucial to remove impurities that could affect the reverse osmosis membrane. These mainly include large particles, residual chlorine, and calcium and magnesium ions. It is important to note that different treatment units must be specifically configured according to the quality of the influent water. Most pure water machine manufacturers cannot effectively help customers solve this problem, which leads to unsatisfactory purification results and shortens the lifespan of key components such as reverse osmosis membranes and ultrapure water columns.

To effectively address this issue, precision filters, activated carbon adsorption filters, and softening resins are designed to specifically remove large particles, residual chlorine, and calcium and magnesium ions from the water, achieving optimal pretreatment results.

Timely replacement of pretreatment consumables (which are relatively inexpensive) is crucial for the long-term stable operation of the ultrapure water machine and for protecting its core components.

Reverse Osmosis

Reverse osmosis uses a high-pressure pump to apply pressure greater than the osmotic pressure difference to a high-concentration solution. Water molecules are forced through a semi-permeable membrane to the lower concentration side. Reverse osmosis can filter out 90%-99% of most contaminants, including inorganic ions. Due to its outstanding purification efficiency, reverse osmosis is a highly effective technology in water purification systems. Because it removes most contaminants, it is often used as a pretreatment method, significantly extending the lifespan of deion exchange columns.

Given the critical role of reverse osmosis in water purification and the high cost of replacing reverse osmosis membranes, we strongly recommend users choose ultrapure water systems with membrane protection features.

To maximize the lifespan of the reverse osmosis membrane and improve its filtration efficiency, a unique technology combined with a leading reverse osmosis flow-limiting design is employed. A flow-limiting valve at the outlet ensures the membrane remains submerged in water, preventing it from drying out and shortening its lifespan. Extending the membrane's lifespan guarantees high-quality output water and improves the cost-effectiveness of the ultrapure water system.

The quality of the reverse osmosis membrane significantly impacts its lifespan and that of the ultrapure water column. Therefore, we strongly suggest users pay attention to reputable brands such as Dow and GE.

Ion Exchange

Ion exchange involves the exchange of positive ions in the water with H+ ions in the ion exchange resin, and the exchange of negative ions with OH- ions in the resin, thus purifying the water. Theoretically, ion exchange can remove almost all ionic substances, achieving an output water resistivity of 18.2 MΩ·cm at 25°C. The quality of water effluent from ion exchange primarily depends on the quality of the ion exchange resin and the exchange efficiency between the water and the resin within the exchange column.

The quality of the ion exchange resin directly impacts the effluent quality and lifespan of the ultrapure water system. Therefore, we strongly recommend users pay attention to the resin brand, such as Dow or Rohm and Haar. The amount of ion exchange resin loaded is directly proportional to its lifespan.

End-of-line treatment

We primarily produce ultrapure water with ultra-low organic content, sterile properties, and pyrogen-free properties according to specific customer requirements. Various treatment methods are available to address different needs, such as ultrafiltration for pyrogen removal, dual-wavelength ultraviolet oxidation for reducing total organic carbon (TOC), and microfiltration for bacterial removal.

Ultrafiltration (UF) membranes are molecular sieves that allow solutions to pass through extremely fine membranes based on size, achieving the separation of molecules of different sizes. This can reduce the pyrogen content in ultrapure water to below 0.001 EU/ml. Dual-wavelength ultraviolet oxidation utilizes photo-oxidation of organic compounds to reduce the total organic carbon concentration in ultrapure water to below 5 ppb.

Conclusion

Producing high-quality ultrapure water is only the first step for ultrapure water systems. For users, the most important issue is maintaining a stable high-quality output water for as long as possible.