Poster: sample homogeneity- a key factor in GPC

By Esther López, Alberto Ortín, Alfredo Roig. Polymer Char, Valencia, Spain.

Sample Homogeneity: A Key Factor in Solution-Based Separation Techniques such as Gel Permeation Chromatography (GPC)

Abstract:

Ensuring sample homogeneity is essential for obtaining accurate and reproducible results in solution-based separation techniques. Heterogeneity may lead to false, distorted, not reproducible peaks, which can compromise the quantification or being misinterpreted as microstructural differences. Examples of heterogeneous samples include those containing undissolved particles, aggregates, or materials synthesized in small lab reactors or derived from recycled streams.

For optimal performance in GPC, one of the experimental variables that contributes to the accuracy of molar mass determination is sample weight or concentration. Achieving this requires working at the lowest possible constant concentration using a representative sample. This presents a challenge: handling a small amount of material while ensuring homogeneity.

Sample pretreatment may involve a wide range of methodologies depending on the sample type. This work focuses on two methods applied to solid polymer samples in granular form. Results obtained without any pretreatment showed a lack of reproducibility, beyond the expected precision in GPC analysis. The first method tested was a thermal method involving a melting process to produce a film for direct use, and the second combined a chemical and thermal method involving dissolution, precipitation, and filtration.

The advantages and limitations of both methods are discussed, with the aim not only to improve reproducibility but also to ensure complete dissolution and filtration of the sample, while avoiding degradation.