Injection artifacts in odorant analysis by gas chromatography
J. Reinhardt, Martin Steinhaus
Abstract
• GC analysis of 14 test odorants revealed artifact formation during hot injection. • Ten different GC injection approaches resulted in substantial differences. • On-column injection was confirmed as gold standard for artifact avoidance. • SPME approaches resulted in the highest degree of artifact formation. • Cedryl acetate is a useful test compound to evaluate critical injection approaches. Odor-active compounds are major quality parameters in food and other consumer products. In the analysis of odorants, gas chromatography (GC) plays a dominant role and is particularly indispensable for odorant screening by GC–olfactometry (GC–O). Whereas artifact formation during workup before GC analysis has been widely discussed, artifact formation during GC injection has not been adequately addressed so far. Using a set of 14 test compounds, we evaluated ten different GC injection approaches. Artifact-producing reactions were particularly 1,2-eliminations. Linalyl acetate additionally showed [1,3]-sigmatropic shifts. On-column injection was confirmed as the gold standard, with virtually zero artifact formation observed not only with classic cold on-column injection in the oven, but also with on-column injection in a programmable temperature vaporizing (PTV) injector. Substantial artifact formation was observed when a high fixed injector temperature was combined with splitless injection. This applied to the injection of liquid samples but even more so to headspace solid-phase microextraction (HS–SPME) approaches. In conclusion, we recommend using on-column injection whenever aiming at a representative odorant spectrum, such as in GC–O. In targeted analysis, critical approaches such as SPME should be carefully tested for artifact formation. For the evaluation of the artifact formation potential of different injection approaches, cedryl acetate emerged as an excellent test compound.