Could Your Laboratory Water Be Affecting Your Test Results?

Water is everywhere in the laboratory. It can be used to prepare reagents, dilute samples, make buffers, rinse glassware, create blanks and standards, support molecular biology workflows and supply analytical equipment.

Because it is so familiar, however, it can be easy to overlook.

A bottle of laboratory water can look completely clear and still contain substances that matter to a sensitive analytical procedure. Ions, organic material, microorganisms or application-specific contaminants may be insignificant for one laboratory task but important for another.

That is why Laboratory Water Purity is about considerably more than whether water looks clean or has simply been described as “purified”.

As laboratories increasingly work with sensitive analytical techniques, molecular biology and trace contaminants such as PFAS, an important question emerges:

Could the water being used in the laboratory become part of the problem the laboratory is trying to measure?

The answer depends on the test.

Niche Healthcare supplies laboratory water covering Type II, Type III and Type IV specifications, EN ISO 3696 Grades 1, 2 and 3, PFAS-Free Water, Nuclease-Free Water and bespoke formulations. The important issue is not simply finding the “purest” water, but understanding which contaminants actually matter for the application.

Water Is Not Just Water Once It Enters a Laboratory

In everyday life, water is generally considered a finished product.

In a laboratory, it can effectively become part of the analytical process.

Consider how many times water can enter a workflow. It might be used to dilute a sample before analysis, prepare a reagent, produce a calibration solution, rinse a vessel or establish a laboratory blank.

If the water introduces something the analytical method is sensitive to, it can potentially contribute to background contamination or interfere with the process.

This is why descriptions such as purified water, deionised water, ultrapure water and laboratory-grade water should not automatically be treated as interchangeable.

The question should instead be:

Pure enough for what?

What Could Actually Be Hiding in Laboratory Water?

The word “contamination” can sound dramatic, but in analytical science it does not necessarily mean that water is visibly dirty or unsafe.

It can simply mean that something is present which matters to the particular method being performed.

Depending on the application, laboratories may need to consider ionic contaminants, organic compounds, microorganisms, particulates, silica, sodium, chloride, total organic carbon or other specified parameters.

Specialist applications introduce additional concerns.

A molecular biology laboratory working with RNA may be concerned about RNase activity. A laboratory testing for PFAS may need to control PFAS background contamination. Another laboratory may principally need water that meets a defined conductivity or resistivity specification.

This is one of the reasons laboratory water should be selected according to the method rather than by a general perception of purity.

Laboratory Water Purity Is Not Simply a Ladder

Type I, Type II, Type III and Type IV terminology can make laboratory water appear straightforward: Type I sounds as though it must always be the “best”, followed by Type II, Type III and Type IV.

That is an oversimplification.

ASTM D1193 establishes reagent-water specifications across Types I to IV and covers different water-quality characteristics. Importantly, the ASTM type numbering originates from historical classification and should not simply be interpreted as a universal ranking of suitability.

A highly purified water may have excellent resistivity and conductivity characteristics but still not have been specifically produced or tested for a specialist requirement such as PFAS or nuclease control.

So the most useful question is not:

“Which type is the best?”

It is:

“Which specification does this particular method require?”

Could the Wrong Water Really Influence a Laboratory Result?

Potentially, which is precisely why analytical methods and laboratory procedures specify water requirements.

The effect depends on what is being measured and the sensitivity of the procedure.

In routine work, a particular contaminant may be present at a level that has no meaningful relevance to the method.

Move into trace or ultra-trace analysis, however, and the situation can be very different.

When the substance being investigated is present at extremely low concentrations, controlling background contamination becomes increasingly important.

This principle is particularly easy to understand when looking at PFAS.

PFAS Testing Shows Why “Pure” May Not Be Specific Enough

Per- and polyfluoroalkyl substances, generally known as PFAS, are a large group of synthetic chemicals.

PFAS analysis presents an interesting laboratory-water challenge because the laboratory is deliberately looking for very small quantities of specific substances. Background contamination therefore needs careful control.

ISO 21675, which covers determination of selected PFAS in water using solid-phase extraction and liquid chromatography-tandem mass spectrometry, states that purified laboratory water can be used but should be confirmed as free from PFAS.

That distinction is important.

Water can be highly purified according to conventional characteristics without that description alone establishing its suitability for PFAS analysis.

For laboratories undertaking PFAS work, PFAS-Free Water is therefore not simply another name for purified water. It addresses a particular analytical concern.

Niche Healthcare’s PFAS-Free Water is intended for trace and ultra-trace PFAS analytical workflows and has a published specification that includes total PFAS below 5 ng/L and individual PFAS below 1 ng/L, including PFOA and PFOS.

Potential applications include laboratory blanks and environmental, drinking-water, groundwater, surface-water and wastewater analysis where the relevant method requires appropriate control of PFAS background contamination.

Why PFAS-Free Water Tells Us Something Bigger About Laboratory Purity

PFAS provides a useful lesson that applies well beyond PFAS analysis:

Purity is application-specific.

Imagine two bottles of water with excellent conventional purity characteristics.

One laboratory wants to use the water for routine reagent preparation.

Another wants to use it as part of a highly sensitive PFAS determination.

Those laboratories are asking completely different questions of the same material.

For the first, conventional laboratory-water characteristics may be the principal concern.

For the second, the laboratory also needs confidence that the water itself will not introduce the substances being investigated.

That is why laboratory water specifications need to evolve alongside increasingly specialised analytical applications.

DNA and RNA Laboratories Face a Completely Different Water Problem

Now move from environmental analysis into molecular biology.

The concern changes again.

Nucleases are enzymes capable of degrading nucleic acids. DNases act on DNA, while RNases act on RNA.

For workflows involving sensitive nucleic-acid material, laboratories may therefore require Nuclease-Free Water rather than choosing water solely according to conductivity or resistivity.

Relevant workflows can include PCR, qPCR, RT-PCR, DNA and RNA preparation, cDNA synthesis, cloning and sequencing where the applicable laboratory protocol specifies nuclease-free water.

Once again, this demonstrates why a general description such as “high-purity water” does not necessarily answer the laboratory’s real question.

A molecular biology laboratory may need to know:

Is it RNase-free?

Is it DNase-free?

Is it appropriate for the specific molecular biology protocol?

Those are different questions from simply asking how electrically conductive the water is.

Would Type II Water Be Enough?

For many laboratory applications, specialist PFAS-free or nuclease-free water will not be necessary.

Type II Analytical Water can be relevant to routine laboratory processes such as appropriate buffer and reagent preparation, laboratory glassware processing, media preparation and compatible laboratory equipment or purification systems.

The Type II Analytical Water supplied by Niche Healthcare has a published specification including 1 MΩ resistivity, 1 µS/cm conductivity, Total Organic Carbon of ≤50 µg/L, sodium ≤5 µg/L, chloride ≤5 µg/L and total silica ≤3 µg/L.

But even here, context matters.

A Type II designation should not automatically be taken to mean that the water meets every microbiological, endotoxin, molecular biology or trace-analysis requirement.

The laboratory method and equipment specification remain the deciding factors.

Where Do Type III and Type IV Water Fit?

Not every laboratory process requires water intended for highly sensitive analytical work.

Type III water can be relevant to more general laboratory applications and as feedwater for further purification where its specification is appropriate.

Type IV pre-treated water can be relevant to compatible technical and feedwater applications. The Niche Healthcare Type IV product, for example, has published characteristics including 0.2 MΩ resistivity, 5 µS/cm conductivity, pH 5.8, sodium ≤50 µg/L and chloride ≤50 µg/L.

This demonstrates another important point.

Using higher-purity water everywhere is not necessarily the objective.

A laboratory can have several different water requirements under one roof. The appropriate specification for an analytical instrument may be very different from the specification needed for feedwater, routine preparation or a specialist molecular workflow.

What About EN ISO 3696 Laboratory Water?

EN ISO 3696 is another specification frequently encountered when laboratory water is being purchased.

ISO 3696 defines three grades of water for analytical laboratory use within a particular scope. ISO states that it covers water for analysis of inorganic chemicals and is not applicable to organic trace analysis, analysis of surface-active agents, or biological or medical analysis. The standard was last reviewed and confirmed in 2023 and remains current.

That scope is extremely important for healthcare and scientific laboratories.

Seeing “ISO” on a water specification should not lead to an assumption that the water is automatically suitable for every laboratory procedure.

Niche Healthcare supplies EN ISO 3696 Laboratory Water in Grades 1, 2 and 3, allowing laboratories to select the appropriate grade where ISO 3696 is the relevant specification.

ASTM Types and ISO 3696 Grades should also not simply be treated as alternative names for exactly the same classifications. The correct standard and specification should be identified for the intended method.

What If None of the Standard Water Grades Fits?

This is where laboratory water becomes particularly interesting.

Some organisations have requirements that do not fit neatly into a standard Type or Grade.

A research project may require a particular conductivity range. A technical process may require water adjusted to a defined pH. A manufacturer may require specific packaging, closures, labels or documentation.

There may also be requirements for buffered solutions, selected antimicrobial additives or additional processing.

In these circumstances, a bespoke water formulation can be produced around a defined specification rather than attempting to adapt the process to an unsuitable standard product.

Niche Healthcare’s bespoke options include custom conductivity ranges, specified pH, buffer systems, selected antimicrobial additives, specialist packaging and tailored documentation. Depending on the agreed specification, options can also include sterile or non-sterile configurations, specialist closures, custom labelling, barcoding, QR coding, nitrogen flushing, ozone flushing and gamma irradiation.

The important word is specified.

A bespoke formulation should never be assumed to possess every specialist characteristic. Requirements such as sterility, endotoxin control, PFAS limits, nuclease status or microbiological limits need to form part of the defined specification where relevant.

Is Deionised Water the Same as Laboratory-Grade Water?

Not necessarily.

This is a useful distinction for both laboratory staff and procurement teams.

Deionisation describes a purification process principally concerned with removing ions.

A defined laboratory-water standard, on the other hand, establishes characteristics that the finished water needs to meet.

The fact that water has been deionised therefore does not automatically establish that it meets a particular ASTM Type, ISO Grade or specialist analytical requirement.

The finished specification is what matters.

The Procurement Problem: “Please Order Some Purified Water”

For healthcare procurement teams, one of the biggest challenges can occur before the water even reaches the laboratory.

A requisition simply asking for “purified water”, “DI water” or “laboratory water” may not contain enough information to identify what is actually required.

A better specification starts with the application.

What is the laboratory doing with the water?

Is there a required ASTM Type or ISO Grade?

Does an analyser manufacturer specify incoming-water characteristics?

Is the water being used for molecular biology?

Is it being used in trace PFAS work?

Are there specific conductivity, resistivity, TOC, microbiological or other requirements?

Does the laboratory require batch traceability or a Certificate of Analysis?

What volume and packaging format are needed?

These questions can be far more useful than simply requesting the “highest purity available”.

Could One Hospital Laboratory Need Several Different Waters?

Absolutely.

Consider a large hospital, university or multidisciplinary scientific laboratory.

One department could require water for routine analytical preparation. Another might need feedwater for purification equipment. A molecular laboratory may require nuclease-free water, while an environmental laboratory could be investigating PFAS at trace concentrations.

The same organisation can therefore legitimately use several different water specifications.

This is why Laboratory Water Purity should be viewed as an application question rather than a single scale running from poor water to good water.

What Should Laboratories Check Before Choosing Water?

The starting point should always be the applicable method, equipment documentation and laboratory quality procedures.

The laboratory should understand which contaminants and characteristics are relevant to the procedure and then compare those requirements with the finished-water specification.

For sensitive procedures, it is also important to consider what happens after the water is manufactured.

Storage vessels, closures, transfer equipment, laboratory consumables and handling can all potentially introduce contamination. High-purity water therefore needs appropriate storage and handling if its required characteristics are to be maintained.

In particularly sensitive workflows, contamination control needs to encompass the complete process rather than simply the original bottle of water.

The Clear Bottle Can Be the Most Overlooked Reagent in the Room

Laboratories naturally focus on sophisticated analysers, reagents, standards, controls and samples.

Water can receive less attention precisely because it looks so simple.

But the more sensitive the analysis becomes, the more important it is to understand what that water is expected to do.

PFAS analysis demonstrates why water may need to be controlled for a very specific family of contaminants.

Molecular biology demonstrates why DNase and RNase considerations can matter independently of conventional purity characteristics.

ISO and ASTM specifications demonstrate why laboratory-water classifications have defined scopes and parameters.

Bespoke formulations demonstrate that sometimes the correct solution is not another standard grade at all, but water produced to a clearly defined application-specific specification.

That makes laboratory water considerably more interesting than it first appears.

Further Information and Authoritative Sources

Type I Ultrapure Water

Type III General Lab Water

Type IV Pre-treated Water

Nuclease-Free Water

PFAS-Free Water

EN ISO 3696 Laboratory Water Grades 1, 2 & 3

Bespoke Water Formulations

International Organization for Standardization – ISO 3696:1987, Water for Analytical Laboratory Use — Specification and Test Methods:
https://www.iso.org/standard/9169.html

ASTM International – ASTM D1193 Standard Specification for Reagent Water:
https://www.astm.org/d1193-24.html

GOV.UK – Monitoring Discharges to Water: CEN and ISO Monitoring Methods:
https://www.gov.uk/government/publications/monitoring-discharges-to-water-cen-and-iso-monitoring-methods/monitoring-discharges-to-water-cen-and-iso-monitoring-methods

Drinking Water Inspectorate – PFAS and Forever Chemicals:
https://www.dwi.gov.uk/pfas-and-forever-chemicals/

Conclusion

Laboratory Water Purity is not simply about achieving the lowest conductivity or selecting the water with the most impressive-sounding grade. It is about understanding what a laboratory is measuring and controlling the characteristics that matter to that particular process.

Routine analytical preparation, equipment feedwater, inorganic chemical analysis, PFAS testing and DNA or RNA workflows can all place very different demands on water.

That is why Type II, Type III, Type IV, EN ISO 3696, PFAS-Free Water, Nuclease-Free Water and bespoke formulations each have distinct roles.

Perhaps the most important question a laboratory can ask about its water is therefore not “How pure is it?”

It is “Pure enough — and appropriately controlled — for what we are trying to measure?”

Published by Maisie McNamara | Clinical Marketing Team

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