title: Quantification aspects of constant pressure (ultra) high pressure liquid chromatography using mass-sensitive detectors with a nebulizing interface.
abstract: The present contribution investigates the quantitation aspects of mass-sensitive detectors with nebulizing interface (ESI-MSD, ELSD, CAD) in the constant pressure gradient elution mode. In this operation mode, the pressure is controlled and maintained at a set value and the liquid flow rate will vary according to the inverse mobile phase viscosity. As the pressure is continuously kept at the allowable maximum during the entire gradient run, the average liquid flow rate is higher compared to that in the conventional constant flow rate operation mode, thus shortening the analysis time. The following three mass-sensitive detectors were investigated: mass spectrometry detector (MS), evaporative light scattering detector (ELSD) and charged aerosol detector (CAD) and a wide variety of samples (phenones, polyaromatic hydrocarbons, wine, cocoa butter) has been considered. It was found that the nebulizing efficiency of the LC-interfaces of the three detectors under consideration changes with the increasing liquid flow rate. For the MS, the increasing flow rate leads to a lower peak area whereas for the ELSD the peak area increases compared to the constant flow rate mode. The peak area obtained with a CAD is rather insensitive to the liquid flow rate. The reproducibility of the peak area remains similar in both modes, although variation in system permeability compromises the 'long-term' reproducibility. This problem can however be overcome by running a flow rate program with an optimized flow rate and composition profile obtained from the constant pressure mode. In this case, the quantification remains reproducibile, despite any occuring variations of the system permeability. Furthermore, the same fragmentation pattern (MS) has been found in the constant pressure mode compared to the customary constant flow rate mode.
authors.affiliation: Vrije Universiteit Brussel, Department of Chemical Engineering (CHIS-IR), Pleinlaan 2, 1050 Brussels, Belgium.
authors.forename: M
authors.initials: M
authors.lastname: Verstraeten
authors.forename: K
authors.initials: K
authors.lastname: Broeckhoven
authors.forename: F
authors.initials: F
authors.lastname: Lynen
authors.forename: K
authors.initials: K
authors.lastname: Choikhet
authors.forename: K
authors.initials: K
authors.lastname: Landt
authors.forename: M
authors.initials: M
authors.lastname: Dittmann
authors.forename: K
authors.initials: K
authors.lastname: Witt
authors.forename: P
authors.initials: P
authors.lastname: Sandra
authors.forename: G
authors.initials: G
authors.lastname: Desmet
mesh_terms: D000336:Aerosols / Q000737:chemistry; D001577:Benzophenones / Q000032:analysis / Q000302:isolation & purification; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004041:Dietary Fats / Q000032:analysis / Q000302:isolation & purification; D013058:Mass Spectrometry / Q000379:methods*; D011084:Polycyclic Aromatic Hydrocarbons / Q000032:analysis / Q000302:isolation & purification; D011312:Pressure; D015203:Reproducibility of Results; D014920:Wine / Q000032:analysis
chemical_list: D000336:Aerosols; D001577:Benzophenones; D004041:Dietary Fats; D011084:Polycyclic Aromatic Hydrocarbons; C052387:cocoa butter