Error margins in the Determination of Molar Mass and Oligomer Content of Polymers
- Size exclusion chromatography (SEC) is still the method of choice for determining the molar mass and molar mass distribution of macromolecules.
It is a liquid chromatographic technique that separates molecules based on their size, respectively their hydrodynamic volume using a porous stationary phase that allows smaller molecules to pass through the pores while excluding larger molecules. The chromatogram from the size separation can be calibrated using polymers of known molar mass resulting in a relative molar mass distribution curve. From this distribution curve molar mass averages and the oligomer content (percentage of peak area smaller than 1000 g/mol and 500 g/mol) of polymers can be derived.
The determination of oligomer content is important, because it is often used in regulatory contexts as a measure of small, mobile and potentially more toxic parts of the polymer. Polymer regulations are of increasing political and social importance. Regulations often set very narrowSize exclusion chromatography (SEC) is still the method of choice for determining the molar mass and molar mass distribution of macromolecules.
It is a liquid chromatographic technique that separates molecules based on their size, respectively their hydrodynamic volume using a porous stationary phase that allows smaller molecules to pass through the pores while excluding larger molecules. The chromatogram from the size separation can be calibrated using polymers of known molar mass resulting in a relative molar mass distribution curve. From this distribution curve molar mass averages and the oligomer content (percentage of peak area smaller than 1000 g/mol and 500 g/mol) of polymers can be derived.
The determination of oligomer content is important, because it is often used in regulatory contexts as a measure of small, mobile and potentially more toxic parts of the polymer. Polymer regulations are of increasing political and social importance. Regulations often set very narrow limits.
SEC has rather large error margins of 10-20% for the molar mass determination performed in different laboratories or on different instruments. These variances are well known to all experts and users and have been investigated in several round robin tests in the past. These resulted in DIN and ISO standards which, in our opinion, no longer meet today's requirements.
As far as we know, the margins of error in determining oligomer content have not yet been investigated. It is expected that the variation will be rather high. This is because it depends on many factors related to the experimental conditions (column sets used, solvent, temperatures, sample preparation) on the one hand, and the data evaluation mechanisms (choice of baseline and peak limits) on the other.
In order to actually measure the error margins and to support this with actual data a round robin test has been performed from June to November 2024 with approx. 40 participating laboratories.
Three different solvents were selected, namely THF, DMAc or DMF and water.
The samples were selected together with all the experts, taking into account a wide range of practical aspects far from narrowly distributed standards: e.g higher distribution range, reduced solubility, included side components, copolymers and dispersions with gel content.
In this contribution we will present the detailed concept of this round robin test and first results.…


| Autor*innen: | Jana FalkenhagenORCiD |
|---|---|
| Koautor*innen: | J.-H. Arndt, T. F. Beskers, A. Eifert, S. Gaul, S. Keune, R. A. H. Peters, S. Schmiedt, A. von Tesmar |
| Dokumenttyp: | Posterpräsentation |
| Veröffentlichungsform: | Präsentation |
| Sprache: | Englisch |
| Jahr der Erstveröffentlichung: | 2025 |
| Organisationseinheit der BAM: | 6 Materialchemie |
| 6 Materialchemie / 6.3 Strukturanalytik | |
| DDC-Klassifikation: | Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Ingenieurwissenschaften und zugeordnete Tätigkeiten |
| Freie Schlagwörter: | Polymers; REACH; Round Robin Tests; Size exclusion chromatography |
| Themenfelder/Aktivitätsfelder der BAM: | Umwelt |
| Umwelt / Circular Economy | |
| Veranstaltung: | SETAC Europe 35th Annual Meeting |
| Veranstaltungsort: | Vienna, Austria |
| Beginndatum der Veranstaltung: | 11.05.2025 |
| Enddatum der Veranstaltung: | 15.05.2025 |
| Verfügbarkeit des Dokuments: | Datei im Netzwerk der BAM verfügbar ("Closed Access") |
| Datum der Freischaltung: | 06.06.2025 |
| Referierte Publikation: | Nein |

