Overview
EN ISO 8655-4:2022 - "Piston-operated volumetric apparatus - Part 4: Dilutors" specifies metrological requirements, maximum permissible errors, marking and user information for laboratory dilutors. The standard applies to dilutors with a sample uptake capacity (In) of 5 µl to 1 ml and a diluent capacity (Ex) of 50 µl to 100 ml. It replaces the 2002 edition and aligns dilutor testing and documentation with the ISO 8655 series for piston-operated volumetric apparatus.
Key topics and requirements
- Scope and principle: Defines operation of dilutors that aspirate a measured sample and deliver it together with a measured diluent volume; covers manual, electrical, pneumatic or hydraulic drives and hand‑held, bottle‑top or bench‑top configurations, including automated analyser components.
- Metrological performance: Requires determination of system trueness and precision using gravimetric methods (total system includes pistons, valves, drive, uptake/delivery probe, tubing and any change‑over unit).
- Maximum permissible errors (MPEs): Tables list MPEs for nominal volumes; the standard also gives a formula to calculate MPEs for selected volumes:
- e_Vs = (V_nom / V_s) × e_Vnom
- Values do not apply below 10% of nominal volume; calculated MPEs are capped at 25%.
- Adjustment: Specifies initial and subsequent adjustment procedures and reference conditions (standard reference temperature 20 °C or 27 °C, 50% RH, 101.3 kPa, using grade 3 water per ISO 3696).
- Marking and user information: Requires clear marking and detailed manufacturer instructions, including evidence and records when subsequent adjustments are performed.
- Testing references: Measurement and verification by ISO 8655-6 (gravimetric reference procedure) or ISO 8655-7 (alternative procedures).
Practical applications and users
EN ISO 8655-4:2022 is intended for:
- Manufacturers - product design, quality control and performance declarations for dilutors.
- Calibration laboratories and test houses - to perform verification, calibration and routine checks using standardized gravimetric methods.
- Clinical, pharmaceutical and research laboratories - to select and validate dilutors for sample preparation, serial dilution and automated workflows.
- Regulatory and QA teams - to ensure documented compliance of volumetric dilutor equipment.
Adoption of this standard helps ensure accurate, traceable dilution steps, reduce assay variability and support compliance in laboratory workflows.
Related standards
- ISO 8655-1 - Terminology, general requirements and user recommendations
- ISO 8655-6 - Gravimetric reference measurement procedure for determination of volume
- ISO 8655-7 - Alternative measurement procedures for determination of volume
Keywords: EN ISO 8655-4:2022, dilutors, piston-operated volumetric apparatus, metrological requirements, maximum permissible errors, gravimetric measurement, calibration, laboratory equipment.
