Laboratory water purity defined.
There several types of water purity available depending on laboratory procedure, from Type III for general use to Type I, the highest purity used in sensitive applications.
To implement a consistent and comprehensive classification system for water purity, we use several vital factors describing water's various properties.
Organic compound levels
Organic compounds that exist in water play are part in the purity of the water. These compounds exist in several forms. The most helpful indicator of organic compound levels in water is the total organic carbon (TOC) content of the solution.
Other Suspended particles can cause water turbidity and are consequently removed from lab water as much as possible. This colloidal material is classified as being less than 0.5 µm in size and is usually made up of iron, silica, aluminum and other organic materials.
The Fouling Index (FI) is frequently used to estimate water potential to block filters under 0.45 µm filter conditions.
Water conductivity: microSiemens per centimeter (µS/cm) at 25oC and equal to resistance and providing a measure of a fluid's ability to conduct electrical current. Conductivity is typically used when evaluating water quality ranging from raw water through to regular drinking water. It provides a valuable, non-specific indication of the level of ion concentration in the water.
The occurrence of biological contaminants like bacteria and other microorganisms is a common concern in untreated water sources. Bacterial levels reported as colony-forming units per millilitre (CFU/ml) are kept low via water purification systems.
Setting Pure Water Standards
In general, classifications of laboratory-grade water include the following types:
Type I: the purest grade of lab water is also referred to as ultrapure water. Type I water is recommended for use in highly critical applications like trace elemental analysis and biotechnology.
Type II: (pure water) recommended source of pre-treated water to feed your Type 1 ultrapure systems. Type II water is usually recommended for buffering preparations for dissolution, microbiology media preparation, and biochemistry analyzers. Type II water can also be used for the preparation of reagents for chemical analysis.
Type III: commonly referred to as instrument feed or portable water, is the lowest form of lab-grade water. Typically this kind of water is produced using Reverse Osmosis (RO), removing up to 99% of contaminants. It is recommended that Type III water be used in glassware washers, humidity chambers or autoclaves.
Several international groups have established some degree of consistency in global water purity standards. Laboratories also adhere to measures outlined by the regional regulatory body overseeing the operation. In 2006, the Clinical and Laboratory Standards Institue (CLSI) moved away from the typical Type I, II and III designations, suggesting that water be 'fit for purpose,' only describing one-grade in considerable detail: Clinical Reagent Laboratory Water. The CLSI has outlined other minor detail grades, such as Special Reagent Water (SRW) and instrument feed water.
The global guidelines for water grade specification include:
- Clinical & Laboratory Standards Institute (CLSI),
- International Organization for Standardization (ISO), and
- American Section of the International Association for Testing Materials (ASTM)
These various measurements differ in the purity concerning the levels of conductivity, total organic carbon (TOC) and bacterial levels. Also, there are grades or application-driven titles in the industry, such as reagent or analytical grade water. And certain pharmacopeias, laboratory-grade water is called purified water.
With a Millipore water purification system, for laboratory research, your laboratory water will be as ultrapure as you need it to be to achieve accurate results for all of your sensitive experiments. A Millipore water system will provide you with a dependable and constant source of pure, uncontaminated water.