We do experiments every day. The reagent for exposure is water. It usually runs through our entire experimental process. Perhaps it is precisely because of the wide availability and easy access of water that we often overlook its influence on the experimental results. Therefore, choosing the right ultrapure water machine for the laboratory can help researchers avoid many unnecessary problems. However, at present, there are numerous brands of ultra-pure water in the domestic market, with uneven quality and huge price differences. This has caused great confusion for buyers who are interested in using ultrapure water machines. They don't know which brand to choose. Based on practical working experience, the following discusses how to choose the right ultrapure water machine. Before discussing how to choose an ultrapure water machine, it is necessary to first understand the difference between pure water and ultrapure water, as well as the current market situation of ultrapure water machines in domestic laboratories.
(1) The difference between pure water and ultrapure water
Before choosing the right laboratory ultrapure water, we have the following concepts that are easy to understand: What is water? What is ultrapure water? What's the difference?
Pure water, also known as purified water, refers to water that meets the hygiene standards for drinking water sources and is sealed in containers through appropriate treatment methods such as electrodialysis, ion exchange, reverse osmosis, and distillation. It contains no additives and is colorless and transparent. It can be drunk directly. Both the space water and distilled water sold on the market are pure water.
Ultrapure water further removes conductive media from pure water and reduces non-dissociated colloidal substances, gases and organic matter in water to a very low level. The resistivity is greater than 18mω·cm, or close to the limit of 18.25 mω·cm. Ultrapure water is a level that is difficult to achieve in general processes. Through reasonable process design, two or more technologies such as microfiltration technology, ultrafiltration technology, reverse osmosis technology, edi technology and ion exchange technology can be established. Ultrapure water can produce a resistivity of 18.20 mω·cm.
Pure water and ultrapure water differ in many aspects. This article only lists some of them, which are summarized as follows:
A. Different conductivities: The conductivity of pure water is between 2 and 10 microseconds per centimeter, and that of ultrapure water is 0.056 microseconds per centimeter.
B. Different manufacturing difficulties. The pure water currently used in the market is basically produced through methods such as reverse osmosis and distillation. Ultrapure water is made on the basis of pure water through a series of complex purification technologies such as photo-oxidation, fine treatment and polishing.
C. The indicators of heavy metals, bacteria and particles also vary greatly. The impurity content of pure water is ppm, and that of ultrapure water is ppb. Simply put, there are no impurities in ultrapure water that is close to theoretical water.
D. The areas used are also different;
E, not the pipe material, the requirements for ultrapure water pipes are more stringent than those for substances.
(2) The current situation of the domestic ultrapure water machine market: At present, the domestic ultrapure water machine market has changed from a situation dominated by "Milibo" to a "dominant situation of a hundred schools of thought contending". Domestic manufacturers of ultrapure water machines have made considerable progress, but the overall technical level is relatively low, and there are only a few manufacturers that can truly produce ultrapure water. Many manufacturers regard pure water with a resistivity of 18.2 m_u.cm as ultrapure water. In fact, this is a misunderstanding in understanding. Because many organic molecules, bacteria and particles do not exist in the form of ions, they will not affect the determination of resistivity. The results show that when the resistivity reading is good, there may still be organic matter, bacteria and other contaminants in the water. Such water cannot be called ultrapure water, while true ultrapure water contains almost no impurities.
