Water is one of the most widely used materials in scientific laboratories. From preparing chemical solutions and rinsing laboratory glassware to conducting analytical testing and biological experiments, laboratory water supports a wide range of procedures.
However, not all water is suitable for every laboratory application. Ordinary tap water contains dissolved minerals, salts, microorganisms and other impurities that may interfere with sensitive laboratory procedures.
Choosing the appropriate laboratory water is therefore important for maintaining testing accuracy, reducing contamination and supporting reliable laboratory results.
In this guide, we explore the different types of laboratory water, common purification methods, water purity requirements and factors to consider when selecting water for laboratory use.
2. What Is Laboratory Water?
Laboratory water is water that has been treated or purified to meet the requirements of a particular scientific or analytical application.
The required purity depends on the intended use.
For example, water used for basic glassware rinsing may have different requirements from water used in high-performance liquid chromatography, molecular biology or trace-element analysis.
Laboratory water quality may be evaluated using parameters such as:
- Electrical conductivity
- Resistivity
- Total organic carbon (TOC)
- Microbial contamination
- Particulate matter
- Dissolved inorganic impurities
No single water grade is appropriate for every laboratory procedure. Laboratories should select water based on the method, equipment manufacturer’s instructions and applicable quality requirements.
3. Types of Laboratory Water
Different types of purified water are produced using different treatment methods.
A. Distilled Water
Distilled water is produced through distillation, a process that involves heating water to generate vapour and then condensing the vapour into liquid.
The process can remove many dissolved salts, non-volatile impurities and other contaminants.
Common applications include:
- General laboratory preparation
- Rinsing certain laboratory equipment
- Preparing selected chemical solutions
- Educational laboratory experiments
- Applications where distilled water is specified
Distillation does not guarantee removal of every contaminant. Certain volatile substances may carry over with the vapour, depending on the process and equipment.
For sensitive applications, the quality of distilled water should be verified against the relevant specifications.
B. Deionized Water
Deionized water is produced by removing dissolved ions from water, commonly through ion-exchange processes.
These ions may include calcium, magnesium, sodium, chloride and other dissolved substances.
Deionized water is commonly used for:
- Preparing certain laboratory solutions
- Rinsing laboratory equipment
- General laboratory procedures
- Feeding selected laboratory water purification systems
- Applications requiring reduced ionic contamination
Deionization primarily targets ionic impurities. It does not necessarily remove organic compounds, microorganisms or particles.
Therefore, deionized water is not automatically suitable for every analytical or biological application.
C. Reverse Osmosis Water
Reverse osmosis (RO) water is produced by forcing water through a semipermeable membrane under pressure.
The membrane reduces many dissolved salts, particles and other contaminants.
Common applications include:
- Laboratory water pretreatment
- General laboratory cleaning
- Feedwater for further purification
- Selected industrial and educational laboratory processes
Reverse osmosis is frequently used as one stage in a multi-stage purification system.
The quality of the resulting water depends on the feedwater, membrane condition, system design and operating conditions.
D. Ultrapure Water
Ultrapure water is highly purified water intended for applications with demanding water-quality requirements.
It may be produced using several purification stages, such as reverse osmosis, ion exchange, activated carbon, ultraviolet treatment and ultrafiltration.
Applications may include:
- High-sensitivity analytical chemistry
- Certain chromatography procedures
- Molecular biology
- Instrumental analysis
- Trace-level testing
Ultrapure water systems may be designed to produce water with a resistivity of up to 18.2 MΩ·cm at 25°C, depending on the system and measurement conditions.
However, resistivity alone does not establish suitability for every application. Organic contamination, particles and microorganisms may also need to be controlled.
4. Laboratory Water Purity Grades
Laboratory water is often classified according to the quality requirements of the application or a relevant standard.
One commonly referenced framework is ASTM D1193, which specifies requirements for reagent water.
The exact classification and specifications should be checked against the current standard and the laboratory’s applicable procedures.
| Water quality | Typical applications |
|---|---|
| General purified water | Routine laboratory preparation and cleaning |
| Analytical-grade water | Analytical procedures with defined purity requirements |
| High-purity water | Sensitive instrumental analysis and specialized testing |
| Ultrapure water | Applications with particularly demanding contamination limits |
These descriptions are general categories, not interchangeable formal grades. A supplier’s product description should be checked against the applicable specification before purchase.
Why Water Purity Matters
Impurities in laboratory water can affect results in several ways.
Chemical interference: Dissolved ions can react with chemicals or affect solution composition.
Analytical interference: Trace contaminants may influence sensitive analytical measurements.
Microbial contamination: Microorganisms can affect certain biological procedures.
Equipment deposits: Minerals can accumulate inside equipment, tubing and heating systems.
Selecting suitable water helps laboratories control these potential sources of error.
5. Laboratory Water Purification Methods
Laboratory water purification systems often combine several treatment methods.
1. Filtration
Filtration removes particles and suspended materials from water.
The filtration method and pore size determine which particles can be retained.
Filtration alone does not remove all dissolved salts or organic contaminants.
2. Reverse Osmosis
Reverse osmosis reduces many dissolved substances and contaminants through a membrane-based process.
It is commonly used as a pretreatment stage in laboratory water purification systems.
3. Ion Exchange
Ion-exchange resins remove dissolved ions from water.
This process is particularly useful when low ionic contamination is required.
Resin condition and system operation influence the quality of the treated water.
4. Activated Carbon
Activated carbon can reduce certain organic compounds and chlorine-related contaminants.
It is often used in pretreatment stages to protect downstream purification components.
5. Ultraviolet Treatment
Ultraviolet treatment is used in some systems to reduce microorganisms or oxidize certain organic compounds, depending on the wavelength and system design.
UV treatment does not automatically remove every contaminant and should be used as part of a suitable purification system.
6. Ultrafiltration
Ultrafiltration uses membranes to reduce certain larger molecules, particles and biological contaminants.
It may be incorporated into systems designed for demanding laboratory applications.
6. Uses of Laboratory Water
Laboratory water is used across a wide range of scientific and industrial environments.
Chemical Laboratories
Water may be used for preparing reagents, diluting solutions, rinsing equipment and conducting chemical experiments.
The required purity depends on the chemical procedure and analytical method.
Pharmaceutical Laboratories
Pharmaceutical laboratories may use purified water for laboratory testing, analytical preparation and other specified applications.
Water used in pharmaceutical manufacturing or regulated processes may be subject to additional pharmacopoeial and regulatory requirements.
Laboratory reagent water should not automatically be considered equivalent to pharmaceutical purified water or water for injection.
Educational Laboratories
Schools, colleges and universities use laboratory water for chemistry experiments, solution preparation and practical demonstrations.
Environmental Testing Laboratories
Environmental laboratories may use purified water for preparing reagents, standards, blanks and certain analytical procedures.
The water quality must be appropriate for the analytes and test methods involved.
Research Laboratories
Research facilities may require different water qualities for chemical analysis, biological research and specialized experiments.
7. How to Choose the Right Laboratory Water
Before purchasing laboratory water or selecting a purification system, consider the following factors.
Application Requirements
Identify the intended application and check the method’s water-quality requirements.
Do not assume that distilled, deionized and ultrapure water are interchangeable.
Purity Specifications
Check relevant specifications for conductivity, resistivity, TOC, microbial content and other parameters where required.
Volume Requirements
Estimate the quantity of water needed daily or weekly.
Laboratories with high water consumption may require a purification system, while smaller laboratories may purchase suitable prepared water.
Storage and Contamination
Purified water can become contaminated during storage and handling.
Consider container material, cleanliness, storage duration and the potential for microbial growth.
Equipment Compatibility
Check the water requirements of instruments such as analytical equipment, autoclaves and laboratory washing systems.
Documentation
For critical applications, review available specifications, quality documentation and testing information.
8. Storage and Handling of Laboratory Water
Purified water quality can change after production.
Appropriate storage and handling practices are therefore important.
- Use clean containers suitable for the water quality and application.
- Keep containers properly closed.
- Avoid unnecessary exposure to air and environmental contamination.
- Follow recommended storage periods.
- Clean storage tanks and dispensing systems according to established procedures.
- Verify water quality when required by the laboratory’s methods.
For sensitive applications, freshly produced water may be required because storage can affect its purity.
Always follow the applicable analytical method and water-system manufacturer’s recommendations.
9. Common Laboratory Water Mistakes
Using Tap Water for Sensitive Analysis
Tap water contains impurities that may interfere with analytical procedures.
Use the water quality specified by the method.
Assuming All Purified Water Is the Same
Distilled, deionized, reverse osmosis and ultrapure water have different characteristics.
Choose based on actual specifications.
Ignoring Water-System Maintenance
Purification systems require appropriate maintenance, including filter or resin replacement and routine performance checks.
Storing Water Incorrectly
Poorly maintained containers and dispensing systems can introduce contaminants.
Not Checking Water Quality
For sensitive applications, laboratories should verify that water meets the required specifications instead of relying solely on a product label.
10. Laboratory Water and Laboratory Supplies in South Africa
Laboratories across South Africa require water for routine testing, research, education and industrial processes.
When purchasing laboratory water or associated purification equipment, laboratories should consider:
- Intended application
- Required purity
- Product specifications
- Available quantities
- Storage requirements
- Delivery and handling
- Equipment compatibility
ZyphorLabs supplies laboratory chemicals, equipment, glassware and plasticware for scientific and industrial applications.
Laboratories can explore the relevant product categories and select supplies according to their operational and technical requirements.
Frequently Asked Questions
What is the difference between distilled and deionized water?
Distilled water is produced by evaporation and condensation, while deionized water is produced by removing dissolved ions, commonly through ion exchange. Neither process necessarily removes every type of impurity.
Is distilled water suitable for all laboratory applications?
No. Some procedures require specific water-quality parameters or ultrapure water. Always follow the requirements of the analytical method or instrument.
What is ultrapure laboratory water?
Ultrapure water is highly purified water intended for demanding applications that require very low levels of ionic and other contaminants.
Can purified laboratory water be stored?
Yes, but storage conditions and duration can affect water quality. Suitable containers, clean handling and appropriate verification are important.
Why is laboratory water quality important?
Water impurities can interfere with chemical reactions, analytical measurements, biological procedures and equipment performance.
Final Thoughts
Laboratory water is a fundamental part of scientific testing, research and routine laboratory operations. Understanding the differences between distilled, deionized, reverse osmosis and ultrapure water helps laboratories select water suitable for their procedures.
The correct choice depends on purity specifications, application requirements, storage conditions and equipment compatibility.
For laboratories sourcing laboratory supplies in South Africa, understanding water quality is an important step towards maintaining consistent and reliable laboratory procedures.
ZyphorLabs supports laboratory procurement through its range of laboratory chemicals, equipment, glassware and plasticware for scientific and industrial applications.
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