Multidimensional gas chromatography investigation of concentration and temperature effects of oxime interconversion on ionic liquid and poly(ethylene glycol) stationary phases

Nolvachai, Yada; Kulsing, Chadin; Trapp, Oliver und Marriott, Philip J. (2019): Multidimensional gas chromatography investigation of concentration and temperature effects of oxime interconversion on ionic liquid and poly(ethylene glycol) stationary phases. In: Analytica Chimica Acta, Bd. 1081: S. 200-208

Abstract

This study develops analytical approaches using comprehensive heart-cut multidimensional gas chromatography (H/C MDGC) to experimentally investigate effects of concentration and temperature on peak shapes and on kinetic analysis of E/Z isomerisation of oximes which undergo various extents of interconversion on D-1 and D-2 separation columns. Different stationary phase combinations were investigated. An SLB-1L76 D-1 column results in good separation of the isomers but with negligible interconversion (D-1(sep)). Precise targeted heart-cuts (H/C;3-15 s windows) and cryogenic trapping of selected sections eluting from this D-1 column allows well controlled E/Z isomer ratios to be delivered to a D-2 poly(-ethyleneglycol) (PEG) phase column. This phase catalyses oxime interconversion, with separation;this is termed D-2(inter). This column set describes a D-1(sep) X D-2(inter) arrangement. The interconversion forward rate constant (k(1)(UE), calculated by using DCXplorer) was found to be independent of the %E isomer (i.e. first order kinetics);k(1)(UE) increased at higher temperature (increased Gibbs activation energies, Delta G(app)). In addition, a long D-1 SLB-IL111 column gave oxime separation with interconversion (D-1(inter)). Comprehensive multiple H/C of the zone performed on the D-2 PEG (D-2(inter)) at 40, 60 and 80 degrees C resulted in a 2D presentation (D-1(inter) X D-2(inter)) with a unique rectangular display of interconversion from each H/C pulse with varied isomer concentration ratios. Data for K-1(UE) from 1DGC analysis suggests underestimation of k(1)(UE)on D-1(inter) SLB-IL111 from the 2D result. The k(1)(UE) value on D-2(inter) PEG column is more reliably evaluated by summation of all the D-2(inter) profiles rather than that obtained from the average value for the individual H/C pulses. (C) 2019 Elsevier B.V. All rights reserved.

• Dokumententyp: Zeitschriftenartikel
• Fakultät: Chemie und Pharmazie > Department Chemie
• Themengebiete: 500 Naturwissenschaften und Mathematik > 540 Chemie
• ISSN: 0003-2670
• Sprache: Englisch