Understanding Water Quality Grades for Laboratory Applications
Water is arguably the most essential reagent in any laboratory. The purity of water is an important factor in obtaining accurate and reliable experimental results. It is especially critical for highly sensitive analytical techniques such as liquid chromatography-mass spectrometry (LC-MS) and inductively coupled plasma mass spectrometry (ICP-MS), as well as genomic methods like next-generation sequencing (NGS) and CRISPR. Moreover, maintaining consistent water quality ensures that experiments are conducted under the same conditions, which is key for obtaining reproducible and comparable results across different studies.
How to choose the right water quality for your lab applications
There are different types of laboratory water, usually defined by specific standards that guide their use in various laboratory applications while also taking cost into account. For example, ultrapure water (Type 1) is more expensive to produce than pure water (Type 2) or reverse osmosis (RO) water (Type 3), but it is essential for highly sensitive laboratory techniques (Figure 1). In contrast, RO water may be sufficiently pure for more basic laboratory tasks.
Figure 1.Water quality grades and their uses in various laboratory applications.
Type 1 Ultrapure Water:
- Critical applications, e.g., HPLC, LC-MS, ICP-MS, GFAA, molecular and cell biology
Type 2 Pure Water:
- Standard applications, e.g., microbiology media, buffers and reagent preparation, washing machines
Type 3 Reverse Osmosis Water:
- Basic lab needs, e.g., non-critical rinsing, heating baths, animal care
Ultrapure (Type 1) water is ion-free (resistivity 18.2 MΩ·cm at 25°C) with low total organic carbon (TOC) content (< 5 ppb). It is recommended for chromatography (HPLC, UHPLC, LC-MS, GC-MS and IC), elemental analysis (AAS, ICP-MS and ICP-OES) and other advanced analytical techniques. It is also needed for many life science applications such as cell and tissue culture, molecular biology and biochemistry applications (e.g. PCR, sequencing, DNA microarrays, nucleic acid gel electrophoresis and Western blotting). Ultrapure water may be used to prepare reagents, cell culture media, buffers and chromatography mobile phases. It may also be used as blank, and to dilute samples and standards.
Pure (Type 2) water is used in general laboratory applications such as the preparation of buffers and pH solutions, and for glassware rinsing. It may also be used for the preparation of microbiological culture media, histology reagents and staining solutions, and for immunodetection techniques (e.g. ELISA). It can feed instruments and lab equipment such as clinical analyzers, stainless steel autoclaves, lab washers, hydrogen generators, weathering and stability test chambers, as well as Type 1 water purification systems.
RO pure (Type 3) water is the lowest laboratory water grade, recommended for glassware rinsing, heating baths, autoclaves, and to feed Type 1 lab water systems. It may also be used in laboratory animal facilities and aquariums.
In addition, the Clinical and Laboratory Standards Institute (CLSI) defines the quality of water required for clinical analyzers as Clinical Laboratory Reagent Water (CLRW).
The choice of water purification system in a laboratory depends on the specific tasks being performed. The most suitable system might produce either pure or ultrapure water, or both. Since no single technology can eliminate all contaminants, multiple purification methods are typically combined to generate pure (Type 2) or ultrapure (Type 1) water.
Contact us if you would like support from a lab water expert in selecting a water purification system for your lab and its range of applications.
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