title: Ionic liquids as novel stationary phases in gas liquid chromatography: inverse or normal isotope effect?
abstract: The separation of deuterated and non-deuterated compounds in gas liquid partitioning chromatography (GLC) on silicone type stationary phase usually results in the inverse isotope effect. With ionic liquids (ILs) as stationary phase, however, this may show a totally different nature. The inverse isotope effect, in which heavier (deuterated) isotopic compounds (isotopologues) elute earlier, is to be expected when van der Waals (London) dispersion forces play a dominant role in the solute-stationary phase interaction. Such (apolar) interactions seem to play only a minor role when ILs are the stationary phases, leading to only a marginal inverse isotope effect, e.g. for the separation of 2,4,6-trichloroanisole and its [(2)H(5)]-isotopologue on 1,12-di(tripropylphosphonium) dodecane bis(trifluoromethansulfonyl) amide (commercialized as SLB-IL59, Supelco). Indeed, with the most polar stationary phase available (commercialized as SLB-IL111; Supelco), this separation showed a normal isotope effect. Further examples are presented and the nature of the isotope effect observed is discussed.
authors.affiliation: Dienstleistungszentrum Ländlicher Raum (DLR) Rheinpfalz, Competence Center for Wine Research, Breitenweg 71, D-67435 Neustadt an der Weinstrasse, Germany. hans-georg.schmarr@dlr.rlp.de
authors.forename: Hans-Georg
authors.initials: HG
authors.lastname: Schmarr
authors.forename: Petra
authors.initials: P
authors.lastname: Slabizki
authors.forename: Sabrina
authors.initials: S
authors.lastname: Müntnich
authors.forename: Carmen
authors.initials: C
authors.lastname: Metzger
authors.forename: Elisa
authors.initials: E
authors.lastname: Gracia-Moreno
mesh_terms: D002849:Chromatography, Gas / Q000379:methods*; D057927:Hydrophobic and Hydrophilic Interactions; D052578:Ionic Liquids / Q000737:chemistry*; D007554:Isotopes / Q000737:chemistry*; D008956:Models, Chemical; D009930:Organic Chemicals / Q000737:chemistry / Q000302:isolation & purification
chemical_list: D052578:Ionic Liquids; D007554:Isotopes; D009930:Organic Chemicals