Determination of volatile compounds in cider apple juices using a covalently bonded ionic liquid coating as the stationary phase in gas chromatography

A chromatographic method for the separation of volatile compounds in Asturian cider apple juices has been developed. For this separation purpose, a monocationic imidazolium-based ionic liquid bearing a reactive terminal iodine atom was synthesized by a quaternization-anion exchange chemical sequence. Next, the gas chromatography (GC) stationary phase was prepared by covalently linking the imidazolium monolith to the reactive silanol groups of the inner capillary wall at 70 °C. This coated GC column exhibited good thermal stability (290 °C), as well as good efficiency (2000 plates/m) in the separation of volatile compounds from Asturian apple cider juices, and was characterized using the Abraham solvation parameter model. The intra-day and inter-day precision of the chromatographic method was evaluated, obtaining relative standard deviations from 3.7 to 12.9% and from 7.4 to 18.0%, respectively. Furthermore, recoveries from 82.5 to 122% were achieved.