Why is laboratory water control important in analytical tests?

Thursday, 17.02.2022. - 11:15

The application of water in everyday life is crucial - without it, there would be no means to comprehensively study the mechanisms that make up life on Earth. In addition to everyday life, the importance of water is imposed in modern research facilities - it is used by most laboratory scientists for their research, however, the water used in one experiment may differ in composition from that used in another. Have you ever wondered what consequences inadequate water quality can have on the accuracy of data, the integrity and repeatability of your research?

Water as a laboratory reagent

For anyone who uses water in the lab, it is important to consider it like any other reagent. Contamination of water with bacteria is a major threat to experiments. Bacteria can not only cause cytotoxic effects on both cultured and primary cells, but secrete various agents into the water, compromising downstream concentration measurements, interfering with antibody function, and adversely affecting nucleic acid integrity. Causes of water pollution can be divided into inorganic (gases, ions dissolved in water, insoluble particles and colloids) and organic sources (metabolic products and synthetic compounds containing carbon and microorganisms) that can drastically change the biological and chemical behavior of water. For this reason, consistent monitoring of water quality is vital to ensure experimental repeatability within and between laboratories over days, weeks, and years. Successfully undertaking this venture requires knowledge of the parameters used to define water quality and the differences between different levels of water purity.

Parameters for water quality assessment

The total water quality is determined by assessing the ionic and organic purity, the level of bacteria and particles. Because water can be contaminated in several ways, a wide range of different parameters need to be measured to determine water quality. There is no absolutely uniform standard for water quality, and deciding whether water quality is appropriate or not depends on the circumstances and the purpose. Several organizations, such as the Institute for Clinical and Laboratory Standards (CLSI; formerly NCCLS, National Committee for Clinical Laboratory Standards) and ASTM International (formerly the American Society for Testing and Materials, ASTM) have published voluntary guidelines on water quality based on degree of purity: ultrapure water type I (clinical laboratory reagent water), pure water type II (special reagent water) and pure water type III (water for instruments).

Download an infographic poster where you can find out what is in your water and how to properly classify it according to the degree of purity.

Although there is a general consensus about the parameters measured to assess water quality, it is important to keep in mind that the actual water quality varies greatly depending on the application the researcher is conducting and the complexity of the data he wants to collect. In most cases, water quality standards should serve as guidelines, offering researchers knowledge on how to determine if their water is a potential source of experimental variability.

Water purification for best results

After determining the composition of existing water, the last step to obtaining laboratory water quality is to implement various purification techniques. As previously mentioned, since water quality requirements vary depending on the intended application, the exact purification technique will also differ.

Various protocols and procedures have been devised to remove impurities from water, and each separate technique specializes in removing one particular type of impurity. As such, a combination of several methods is usually required to obtain water of sufficient quality for experimental purposes:

  • reverse osmosis (RO) - reverse osmosis (RO), like filtration, uses a filter to separate unwanted elements from the water. However, by reverse osmosis, water penetrates the semipermeable membrane (MWCO: 100-200 Da) 2 using hydraulic pressure to overcome the opposite osmotic pressure generated by the concentration gradient across the membrane. The end result is that the solutes are kept on the pressure side as the solvent - in this case, water - passes. The RO technique is effective in removing 90-99% of particles, ions, organic matter and microorganisms in one step.
  • electrodeionization (EDI) - Ion exchange and electrodeionization (EDI) can also be used to deionize water. In both techniques, the ions are extracted using an ion exchange support. Direct ion exchange replaces unwanted ions for H + and OH- ions, constituents of water, while EDI applies current to pull ions through semipermeable exchangeable membranes at the anode or cathode, depending on the polarity. Ion exchange carriers will be depleted over time, but EDI solves this problem by using a weak electric current to continuously regenerate the carrier. Deionization techniques will not remove any other contaminants from the water, and deionization equipment can easily become contaminated if the water has not been pre-treated before deionization.

No matter what water purification technique you need for your applications, advanced technology has made it possible to perform water purification sequentially and automatically with a single instrument, at the touch of a button. It is on this principle that our Arium® type I, II and III laboratory water preparation systems operate, enabling faster and more reliable laboratory work, while ensuring long-term economy.

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