Overview - ISO 16014-2:2019 (Universal calibration method)
ISO 16014-2:2019 is the ISO standard for determining the average molecular weight and molecular weight distribution of polymers using size-exclusion chromatography (SEC) with the universal calibration approach. Published as Part 2 of the ISO 16014 series (third edition, 2019), the standard specifies how to build and use a universal calibration curve - plotting lg([η]·M) versus elution time or volume - and how to convert SEC elution data into near-absolute molecular-weight values using the Mark–Houwink–Sakurada relationship ([η] = K·M^a).
Note: ISO 16014-2 is classed as a relative method (see ISO 16014-1) but, according to Annex A, typically yields average molecular weights and distributions equal or very close to absolute values.
Key topics and technical requirements
- Universal calibration curve: prepare using narrow-distribution polymer standards (e.g., polystyrene, PMMA); plot lg([η]·M) vs elution time (t) or volume (V = t·Q).
- Intrinsic viscosity and Mark–Houwink–Sakurada equation: use [η] = K·M^a to compute intrinsic viscosity or use directly measured [η] under the same elution conditions.
- Calculation steps:
- Build universal calibration curve from standards.
- Determine [η] or use K and a values to compute [η] for sample fractions.
- Calculate molecular weight M at each elution time and compute average molecular weights, polydispersity, and differential/cumulative distributions per Clauses 9.2–9.4.
- Data acquisition & processing: follows procedures in ISO 16014-1 (baseline correction, signal intensity H at each t).
- Limitations and applicability: method assumes no specific interaction with column packing and that K and a are reasonably constant. It can be unreliable for strongly interacting polymers or extensively long-chain branched materials (see Annex A).
- Documentation: include calibration curve, standard information, apparatus and measurement parameters, and results in the test report (Clauses 11.2–11.4).
Applications and who uses this standard
- Laboratories performing polymer characterization by SEC seeking more universal / near-absolute molecular-weight results.
- R&D and QC teams in plastics, polymer manufacturing, coatings, adhesives, and materials science.
- Instrument vendors and service labs validating SEC systems and calibration procedures.
- Academic researchers comparing polymer architectures (linear vs branched) and seeking consistent inter-laboratory results.
Related standards
Keywords: ISO 16014-2:2019, universal calibration, size-exclusion chromatography, SEC, molecular weight distribution, intrinsic viscosity, Mark–Houwink–Sakurada, polymer characterization.