1、 How to choose a laboratory ultrapure water machine:

Key points for selecting an ultrapure water machine: We conduct experiments every day and come into contact with the most common reagent than water, which usually runs through our entire experimental process. Perhaps due to the widespread availability of water, we often overlook its impact on experimental results. Therefore, choosing a laboratory ultrapure water machine correctly can help researchers avoid many unnecessary troubles. However, there are many brands of ultrapure water machines in the domestic market, with varying quality and huge price differences, which has caused great confusion for buyers who intend to use ultrapure water machines. They do not know which brand to choose. Based on my actual work experience, let's talk about how to choose a suitable ultrapure water machine. Before discussing how to choose an ultrapure water machine, let's first understand the difference between pure water and ultrapure water, as well as the current market situation of ultrapure water machines in domestic laboratories.

2、 The difference between pure water and ultrapure water

Before choosing the laboratory ultrapure water machine correctly, we must have a good understanding of the following concepts:

What is pure water? What is ultrapure water? What is the difference between the two?

Pure water, also known as purified water, refers to water that meets the hygiene standards for drinking water and is sealed in a container using methods such as electrodialysis, ion exchange, reverse osmosis, distillation, and other appropriate processing techniques. It is colorless and transparent, and can be consumed directly. The space water and distilled water sold in the market are all pure water. Ultra pure water is a process that further removes almost all conductive media from water on the basis of pure water, and also removes colloidal substances, gases, and organic compounds that do not dissociate from water to a very low level. The resistivity is greater than 18M Ω* cm, or close to the limit value of 18.25M Ω* cm. Ultra pure water is a level that is difficult to achieve in general processes. Two or more technologies from microfiltration, ultrafiltration, reverse osmosis, EDI, and ion exchange can be used to produce ultra pure water with a resistivity of up to 18.20M Ω* cm through reasonable process design and equipment selection.

There are many differences between pure water and ultrapure water, and only some of them are listed here. They are summarized as follows:

A、 The conductivity varies, with pure water having a conductivity between 2-10 us/cm and ultrapure water having a conductivity of 0.056 us/cm;

B、 The difficulty level of manufacturing varies. Currently, pure water used in the market is mostly produced through methods such as reverse osmosis and distillation, while ultrapure water is produced through a series of complex purification techniques such as photooxidation, precision treatment, and polishing on the basis of pure water.

C、 There are also significant differences in indicators such as heavy metals, bacteria, and particle count. The impurity content in pure water is at the ppm level, while in ultrapure water it is at the ppb level. Simply put, there are no impurities in ultrapure water, which is close to theoretical water.

D、 The fields of use are also different;

E、 The requirements for the material of the conveying pipeline are also different, and ultrapure water has much stricter requirements for the material of the conveying pipeline than ultrapure water.

(2) The current situation of the domestic ultrapure water machine market

At present, the domestic market for ultrapure water machines has shifted from a situation where "Mi Li Bo" dominated the world in the past to a situation where "one company dominates and a hundred schools of thought compete". Domestic ultrapure water machine manufacturers have made significant progress, but their overall technical level is relatively low, and there are still relatively few manufacturers that can truly produce ultrapure water. Many manufacturers interpret pure water with a resistivity of 18.2 M Ω. cm as ultrapure water. However, this is a misconception because many organic molecules, bacteria, and particles do not exist in ionic form, which does not affect the determination of resistivity. As a result, when the resistivity reading is good, there may still be contamination from organic matter, bacteria, and other substances in the water. This type of water cannot be called ultrapure water. True ultrapure water contains almost no impurities, so domestic manufacturers need to continue to work hard in this area.