Featured Answer: What Is ISO 8655?
ISO 8655 is an international standards series covering piston-operated volumetric apparatus (POVA), including piston pipettes, burettes, dilutors, dispensers, and certain manually operated precision laboratory devices used to measure or deliver liquids. The standards establish requirements and test methods addressing areas such as design, metrological performance, maximum permissible errors, calibration, testing, and user considerations.
For laboratories that depend on accurate liquid handling, ISO 8655 provides a standardized framework for evaluating whether volumetric equipment performs within defined requirements. At International Process Solutions (IPS), we recognize the importance of reliable pipette calibration and documented measurement results for pharmaceutical, biotechnology, life science, research, educational, and other laboratory environments.
What Does ISO 8655 Cover?
ISO 8655 is not simply a single procedure for checking a pipette. It is a multi-part international standard addressing different types of piston-operated volumetric apparatus and the methods used to evaluate their performance.
The standard is particularly important for laboratories using equipment that repeatedly aspirates, measures, or dispenses relatively small liquid volumes.
Examples include:
- Single-channel piston pipettes
- Multichannel piston pipettes
- Piston burettes
- Dilutors
- Dispensers
- Manually operated precision laboratory syringes
- Other piston-operated volumetric equipment within the applicable scope
The ISO 8655 series provides a common technical foundation that manufacturers, calibration laboratories, testing facilities, and equipment users can reference when evaluating liquid-handling performance.
ISO 8655 Parts Explained
The ISO 8655 series is divided into multiple parts so requirements can be applied to specific equipment types and measurement procedures.
Organizations should always verify the current applicable edition and relevant part of ISO 8655 for their equipment and calibration program.
ISO 8655-1: Terminology, General Requirements and User Recommendations
ISO 8655-1 establishes general concepts applicable to piston-operated volumetric apparatus. It provides terminology and overarching requirements while addressing considerations relevant to users.
ISO 8655-2: Pipettes
ISO 8655-2 addresses pipettes and is one of the most relevant portions of the series for laboratories using adjustable-volume or fixed-volume piston pipettes.
ISO 8655-3: Burettes
ISO 8655-3 applies to piston burettes and establishes requirements for evaluating their volumetric performance.
ISO 8655-4: Dilutors
ISO 8655-4 addresses dilutors used for controlled liquid-volume and dilution applications.
ISO 8655-5: Dispensers
ISO 8655-5 covers dispensers used for repetitive and controlled liquid delivery.
ISO 8655-6: Gravimetric Reference Measurement Procedure
ISO 8655-6 addresses the gravimetric reference measurement procedure used to determine delivered volume.
ISO 8655-7: Alternative Measurement Procedures
ISO 8655-7 addresses alternative measurement procedures for determining the performance of piston-operated volumetric apparatus.
ISO 8655-8: Photometric Reference Measurement Procedure
ISO 8655-8 addresses photometric reference measurement procedures that may be appropriate for certain liquid-handling applications.
ISO 8655-9: Manually Operated Precision Laboratory Syringes
ISO 8655-9 addresses manually operated precision laboratory syringes.
ISO 8655-10: User Guidance, Competence, Training and POVA Suitability
ISO 8655-10 addresses user guidance and considerations involving competence, training, and the suitability of piston-operated volumetric apparatus.
ISO 8655 Pipette Calibration Explained
For piston pipettes, calibration evaluates the relationship between the selected or nominal volume and the volume actually delivered under defined conditions.
A pipette may appear to operate normally while delivering a volume that differs from its expected value. Small discrepancies may not be visually apparent, particularly when working in microliter ranges.
A properly controlled calibration procedure provides objective measurement data that can be used to evaluate pipette performance.
How Gravimetric Pipette Calibration Works
A gravimetric pipette calibration typically begins with suitable test equipment and controlled conditions.
The pipette is prepared according to the applicable procedure. Test liquid is aspirated and dispensed, and the dispensed mass is recorded using an appropriate balance.
Multiple measurements are taken at the required test volumes. The mass measurements are converted to volume using an appropriate conversion factor that accounts for relevant properties and environmental conditions.
The resulting data can then be evaluated for systematic and random measurement error.
Systematic Error in Pipette Calibration
Systematic error represents the difference between the mean measured volume and the selected or nominal volume.
A pipette can be highly repeatable while still consistently delivering the wrong amount. A pipette that repeatedly dispenses nearly identical volumes is not necessarily accurate if those volumes are consistently above or below the intended value.
Random Error in Pipette Calibration
Random error relates to the variation among repeated measurements.
The amount of variation provides information about the pipette’s repeatability. A reliable calibration evaluation therefore considers both the average delivered volume and how consistently the instrument reproduces its liquid deliveries.
Maximum Permissible Errors Under ISO 8655
ISO 8655 establishes maximum permissible errors for applicable piston-operated volumetric apparatus.
The allowable values depend on factors such as equipment type and nominal or selected volume. There is not one universal accuracy tolerance that can be applied to every pipette.
Laboratories should use the appropriate requirements for the specific device being evaluated.
Why Pipettes Are Tested at Multiple Volumes
For variable-volume pipettes, testing only at the maximum setting may not provide sufficient information about performance throughout the instrument’s usable range.
A pipette may perform correctly at one setting while showing unacceptable performance at another. Testing multiple settings can identify problems that would otherwise remain undetected.
Environmental Conditions in ISO 8655 Calibration
Environmental conditions can influence high-precision volumetric measurements.
Important factors can include:
- Air temperature
- Water temperature
- Atmospheric pressure
- Relative humidity
- Evaporation
- Vibration
- Air movement
- Stability of the weighing environment
These influences become increasingly important as test volumes decrease.
The Role of Water in Gravimetric Pipette Calibration
Water is commonly used as the test liquid in gravimetric calibration procedures.
Converting measured water mass into delivered volume requires consideration of physical conditions. Water density changes with temperature, and buoyancy effects can influence high-accuracy mass measurements.
Appropriate gravimetric procedures therefore use a conversion factor rather than relying on an oversimplified assumption that mass and volume are always numerically interchangeable.
ISO 8655 and Measurement Uncertainty
Measurement uncertainty is an important consideration in pipette calibration.
Potential contributors can include balance calibration uncertainty, balance resolution, repeatability, environmental measurements, evaporation, water temperature, atmospheric pressure, conversion calculations, test procedures, and operator technique.
An uncertainty evaluation helps establish the level of confidence associated with the reported calibration result.
ISO 8655 vs. ISO/IEC 17025
ISO 8655 and ISO/IEC 17025 serve different but complementary purposes.
ISO 8655 focuses on piston-operated volumetric apparatus and associated measurement procedures and performance requirements.
ISO/IEC 17025 establishes general requirements for the competence, impartiality, and consistent operation of testing and calibration laboratories.
At International Process Solutions, our ISO/IEC 17025-accredited pipette calibration capabilities support customers that require documented, technically controlled calibration services.
ISO 8655 Calibration vs. Manufacturer Specifications
A pipette manufacturer’s specifications and ISO 8655 requirements are not necessarily identical.
Depending on an organization’s quality requirements, pipette performance may be evaluated against:
- Applicable ISO 8655 requirements
- Manufacturer specifications
- Internal laboratory tolerances
- Method-specific requirements
- Process-specific acceptance criteria
The acceptance criteria should be clearly established before calibration results are interpreted.
Common Causes of Pipette Calibration Failure
A pipette can move outside acceptable performance limits because of worn seals, damaged O-rings, contaminated components, piston wear, mechanical damage, leakage, corrosion, improper maintenance, excessive use, accidental drops, or chemical exposure.
Operator technique can also produce poor liquid-handling results even when the pipette itself is functioning correctly.
How User Technique Affects Pipette Performance
Pipetting technique can significantly influence delivered volume.
Important variables include pipette angle, immersion depth, aspiration speed, dispensing speed, tip pre-wetting, tip selection, plunger operation, temperature equilibration, and consistency between operators.
Laboratories performing sensitive analytical procedures should combine properly calibrated equipment with documented pipetting techniques and appropriate personnel training.
How Often Should Pipettes Be Calibrated?
Calibration frequency should be determined using factors such as:
- Frequency of use
- Pipette type
- Historical calibration results
- Manufacturer recommendations
- Application criticality
- Required measurement accuracy
- Laboratory quality procedures
- Regulatory requirements
- Risk associated with incorrect volume delivery
Historical calibration data can be particularly valuable when establishing or reviewing calibration intervals.
ISO 8655 for Pharmaceutical and Biotechnology Laboratories
Accurate liquid handling is essential in many pharmaceutical and biotechnology applications.
Pipettes may be used for sample preparation, standard preparation, reagent addition, serial dilution, assay preparation, quality control testing, research and development, analytical procedures, microbiological testing, and molecular biology workflows.
For laboratories operating under GMP or other controlled quality systems, documented pipette calibration can form an important part of the overall equipment control program.
ISO 8655 Calibration Documentation
Depending on the calibration service and applicable requirements, a pipette calibration certificate may include:
- Pipette manufacturer
- Model
- Serial number or equipment identification
- Pipette type
- Nominal volume
- Test volumes
- Measurement results
- Systematic error
- Random error
- Applicable acceptance criteria
- Reference standards
- Calibration date
- Environmental conditions where relevant
- Measurement uncertainty where applicable
- Calibration status
- As-found and as-left information when applicable
Accurate records are particularly important during quality audits, regulatory inspections, equipment investigations, and internal reviews.
As-Found and As-Left Pipette Calibration Results
As-found data documents the condition of the pipette before adjustment or corrective work.
As-left data documents performance after applicable adjustment, maintenance, or repair.
If a pipette is discovered outside its required tolerance, as-found results can help the laboratory evaluate whether previous work performed with that pipette could have been affected.
Does a Pipette Need Adjustment If It Fails Calibration?
A pipette that fails its applicable acceptance criteria may require adjustment, maintenance, repair, or further evaluation.
Calibration determines and documents performance. Adjustment changes the instrument in an attempt to bring its performance closer to the required value.
A typical process may include:
As-found calibration → evaluation → adjustment or repair if authorized → as-left calibration
Frequently Asked Questions About ISO 8655
What Equipment Does ISO 8655 Apply To?
ISO 8655 applies to specified types of piston-operated volumetric apparatus, including pipettes, burettes, dilutors, dispensers, and other equipment addressed within the individual parts of the standard.
Is ISO 8655 Only for Pipettes?
No. Pipettes are a major part of ISO 8655, but the standards series covers several categories of piston-operated volumetric apparatus and associated measurement procedures.
What Is the ISO Standard for Pipette Calibration?
The ISO 8655 series provides internationally recognized requirements and procedures relevant to piston pipettes and their calibration or testing. The exact parts used depend on the device and measurement procedure.
What Is the Difference Between ISO 8655 and ISO/IEC 17025?
ISO 8655 addresses piston-operated volumetric apparatus and relevant measurement procedures. ISO/IEC 17025 establishes competence requirements for testing and calibration laboratories.
Does ISO 8655 Require Gravimetric Calibration?
The ISO 8655 series includes a gravimetric reference measurement procedure, while other parts address alternative and photometric measurement approaches. The appropriate method depends on the equipment, application, and applicable requirements.
Why Are Repeated Measurements Required During Pipette Calibration?
Repeated measurements provide data for evaluating both the average delivered volume and variation between individual deliveries, allowing systematic and random error to be assessed.
Can a Pipette Be Precise but Inaccurate?
Yes. A pipette can repeatedly deliver nearly the same amount while consistently delivering above or below the target volume. This is why both systematic and random error are evaluated.
ISO 8655 Pipette Calibration Services from International Process Solutions
At International Process Solutions, we understand that laboratories depend on pipettes as precision measurement instruments. Their performance can directly affect the quality and reliability of laboratory data.
We provide professional calibration services for organizations throughout Southern and Northern California, including laboratories in Orange County, San Diego, San Carlos, and surrounding regions.
Our calibration services support pharmaceutical, biotechnology, life science, research, education, manufacturing, GMP-regulated operations, and quality control laboratories.
We provide on-site and laboratory calibration services, allowing customers to select an approach that fits their equipment, operational requirements, and quality programs.
The Bottom Line on ISO 8655 Standards
ISO 8655 provides an internationally recognized framework for piston-operated volumetric apparatus, including pipettes, burettes, dilutors, dispensers, and associated measurement procedures.
For pipettes, the standards provide a technical foundation for evaluating systematic error, random error, volumetric performance, testing conditions, and measurement procedures.
At International Process Solutions, we help laboratories maintain confidence in critical measurement equipment through professional calibration services, documented results, and ISO/IEC 17025-accredited pipette calibration capabilities.
For laboratories where microliters can influence the integrity of an entire analytical process, properly controlled pipette calibration provides the documented measurement confidence needed to support accurate testing, consistent processes, quality assurance, and regulatory readiness.
