Overview
ISO/TR 16153:2023 - Determination of uncertainty for volume measurements of a piston-operated volumetric apparatus using a photometric method - provides detailed guidance on evaluating measurement uncertainty when calibrating piston-operated volumetric apparatuses (POVA) by photometric procedures. It supports the photometric reference method in ISO 8655-8 and the photometric procedure in ISO 8655-7:2022, Annex B, and aligns with ISO/IEC Guide 98-3 (GUM). The report includes worked examples, input modelling, and practical corrections (e.g., pressure and temperature effects).
Key technical topics and requirements
- Measurement modelling: Mathematical relationships linking the measurand (delivered volume) to input quantities (absorbances, volumes, densities, dilution ratios, calibration constant).
- Photometric system inputs: Handling of dual-dye ratiometric measurements using CuCl (copper(II) chloride) and Ponceau S solutions; absorbances at 520 nm and 730 nm; preparation and use of calibrator solutions.
- Uncertainty components:
- Standard uncertainty contributions from the photometric measurement (absorbance measurements, calibrator volumes, dilution ratio, calibration constant).
- POVA-related components (resolution, setting, air cushion effects, cubic thermal expansion coefficient).
- Liquid delivery process components (repeatability, reproducibility, handling).
- Uncertainty calculation procedure: Steps following ISO/IEC Guide 98-3 - express model, estimate expected values, determine standard uncertainties and degrees of freedom, account for covariances, compute sensitivity coefficients, combine uncertainties, and apply coverage factor k to obtain expanded uncertainty.
- Practical corrections and annexes:
- Worked example for mean delivered volume and expanded uncertainty.
- Annex A: estimating uncertainty in use of a single delivered volume.
- Annex B: corrections for pressure changes and temperature-related volume correction.
Practical applications and who should use this standard
ISO/TR 16153:2023 is essential for:
- Calibration and testing laboratories performing POVA calibration by photometric methods.
- Metrology and quality assurance professionals who need to estimate measurement uncertainty for pipettes, dispensers and other piston-operated volumetric apparatus.
- Manufacturers of pipettes and laboratory dosing equipment preparing calibration procedures or uncertainty statements.
- Clinical, pharmaceutical and research labs requiring traceable volume measurements and compliant calibration documentation.
Benefits include consistent uncertainty budgets, improved conformity with ISO 8655 requirements, and clearer reporting of combined standard uncertainty, expanded uncertainty, and uncertainty in use.
Related standards
- ISO 8655-1 - Terminology and general requirements for piston-operated volumetric apparatus
- ISO 8655-7:2022 - Photometric procedures (Annex B referenced)
- ISO 8655-8 - Photometric reference measurement procedure
- ISO/IEC Guide 98-3 (GUM) - Guide to the expression of uncertainty in measurement
Keywords: ISO/TR 16153:2023, uncertainty, piston-operated volumetric apparatus, photometric method, ISO 8655, POVA calibration, measurement uncertainty, photometric measurement, repeatability, reproducibility.