Ultra-pure water is a vital component of
more and more laboratory procedures. Impurities in the water can cause various
problems ranging from direct interaction with the ion being measured to
overlapping peaks, shifts in background signals, inhibition of electrode
response and interference with column activity. These interferences can be
caused by inorganic, organic, colloidal or microbiological impurities, all of
which must be controlled and reduced to acceptable levels.
In the purification of drinking water, it
is treated sequentially by filtration, passage through activated carbon to
remove chlorine, reverse osmosis (RO) to remove over 95% of all types of
impurities (inorganic and organic), and all particulates larger than 0.2 mm and microorganisms. The water is recirculated through an
electro-deionization stack to remove the remaining ionic impurities and an
ultraviolet-irradiation chamber to break down bacteria and organic molecules.
The water produced contains sub-ppb levels of ionic impurities and low ppb
level of total organic carbon (TOC). The impurities are at or below detection
limits by even the most sensitive techniques. The purification process is
combined with a 0.2 micron filter to polish the pretreated water.
Type I reagent-grade water with extremely low organic-carbon content, has a resistivity of 18.3 Mohm·cm and a total organic carbon content of less than 5 ppb. This water is suitable for such analytical applications as High Performance Liquid Chromatography (HPLC), Atomic Absorption Spectroscopy (AAS), Total Organic Carbon (TOC), Gas Chromatography followed by Mass Spectrometry (GC/MS), Ion Chromatography (IC), Inductivity Coupled Plasma Spectroscopy (ICP) and ICP/MS, electrochemical determination of traces of metals and other analytical procedures. The use of ultra-pure water is essential for the preparation of samples, blanks and standards, and also for eluents and other reagents.
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