Reproducibility of inverse gas chromatography under infinite dilution: Results and interpretations of an interlaboratory study

• Published in: Journal of Chromatography A 2024-01, Vol.1714, p.464526, Article 464526
• Main Authors: Sygusch, Johanna, Duempelmann, Ralf, Meyer, Ralf, Adamska, Katarzyna, Strzemiecka, Beata, Enke, Dirk, Rudolph, Martin, Brendlé, Eric
• Format: Article
• Language: English
• Subjects: energy; gas chromatography; Inverse gas chromatography; Lactose; Silica; Specific interaction parameter; Surface energy
• ISSN: 0021-9673
• DOI: 10.1016/j.chroma.2023.464526

•This is the first interlaboratory study using different types of IGC instruments.•Analysis of silica and lactose with different IGC devices under defined conditions.•The observed raw data of individual measurements vary significantly.•The calculated dispersive surface energy components vary by 20 % for both materials.•A standard powder and protocol for IGC analysis is needed for future evaluations. Over the last years, inverse gas chromatography (IGC) proved to be a versatile and sensitive analytical technique for physicochemical properties. However, the comparability of results obtained by different users and devices remains a topic for debate. This is the first time, an interlaboratory study using different types of IGC instruments is reported. Eight organizations with different IGC devices defined a common lab measurement protocol to analyse two standard materials, silica and lactose. All data was collected in a standard result form and has been treated identically with the objective to identify experimentally observed differences and not potentially different data treatments. The calculated values of the dispersive surface energy vary quite significantly (silica: 22 mJ/m2 - 34 mJ/m2, lactose 37 mJ/m2 - 51 mJ/m2) and so do the ISP values and retention volumes for both materials. This points towards significant and seemingly undiscovered differences in the operation of the instruments and the obtained underlying primary data, even under the premise of standard conditions. Variations are independent of the instrument type and uncertainties in flow rates or the injected quantities of probe molecules may be potential factors for the differences. This interlaboratory study demonstrates that the IGC is a very sensitive analytical tool, which detects minor changes, but it also shows that for a proper comparison, the measurement conditions have to be checked with great care. A publicly available standard protocol and material, for which this study can be seen as a starting point, is still needed to judge on the measurements and the resulting parameters more objectively.