Investigation to find a suitable reference material for use as an inverse gas chromatography system suitability test

The purpose of this study was to find a suitable material for use as a system suitability test material for inverse gas chromatography (IGC). The purpose of a system check is to measure the variability of the instrument being used rather than the material being analysed. Having such a system check for IGC enables a basic GMP requirement to be met. IGC results can then be used in regulatory submissions to support other already established techniques for characterising pharmaceutical materials. α-Alumina was chosen because it is inorganic, stable at high temperatures, resistant to hydration and is already established as a system check material for surface area determination by nitrogen adsorption. Two columns (1 and 2) packed from the same reference sample jar of α-alumina and analysed under the same conditions yielded dispersive surface energies of 34.8 ± 0.8 and 35.3 ± 0.8 mJ/m2, respectively, at 15% RH. Column 1 was analysed on a second IGC system, and gave a dispersive surface energy of 34.7 ± 0.2 mJ/m2. No significant change was evident after 7 months storage under laboratory ambient conditions. Analysis of material from a second reference sample jar of α-alumina produced results not noticeably different to those of the first, yielding a dispersive surface energy of 35.3 ± 0.1 mJ/m2. A change was seen to occur in the surface properties α-alumina when the humidity was varied, but the change appeared to be consistent across the two columns reported. Based upon the data in this experimental, α-alumina appears to be a suitable material for use as a system suitability test material for IGC.