title: Optimization of parameters affecting signal intensity in an LTQ-orbitrap in negative ion mode: A design of experiments approach.
abstract: A multistage optimization of all the parameters affecting detection/response in an LTQ-orbitrap analyzer was performed, using a design of experiments methodology. The signal intensity, a critical issue for mass analysis, was investigated and the optimization process was completed in three successive steps, taking into account the three main regions of an orbitrap, the ion generation, the ion transmission and the ion detection regions. Oleuropein and hydroxytyrosol were selected as the model compounds. Overall, applying this methodology the sensitivity was increased more than 24%, the resolution more than 6.5%, whereas the elapsed scan time was reduced nearly to its half. A high-resolution LTQ Orbitrap Discovery mass spectrometer was used for the determination of the analytes of interest. Thus, oleuropein and hydroxytyrosol were infused via the instruments syringe pump and they were analyzed employing electrospray ionization (ESI) in the negative high-resolution full-scan ion mode. The parameters of the three main regions of the LTQ-orbitrap were independently optimized in terms of maximum sensitivity. In this context, factorial design, response surface model and Plackett-Burman experiments were performed and analysis of variance was carried out to evaluate the validity of the statistical model and to determine the most significant parameters for signal intensity. The optimum MS conditions for each analyte were summarized and the method optimum condition was achieved by maximizing the desirability function. Our observation showed good agreement between the predicted optimum response and the responses collected at the predicted optimum conditions.
authors.affiliation: Department of Pharmacognosy and Natural Products Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens, 15771 Athens, Greece.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Lemonakis
authors.affiliation: Department of Pharmacognosy and Natural Products Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens, 15771 Athens, Greece.
authors.forename: Alexios-Leandros
authors.initials: AL
authors.lastname: Skaltsounis
authors.affiliation: Department of Pharmacology, University of Athens Medical School, 11527 Athens, Greece.
authors.forename: Anthony
authors.initials: A
authors.lastname: Tsarbopoulos
authors.affiliation: Department of Pharmaceutical Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens, Panepistimioupolis Zografou, 15771 Athens, Greece. Electronic address: vgikas@pharm.uoa.gr.
authors.forename: Evagelos
authors.initials: E
authors.lastname: Gikas
mesh_terms: D057888:Iridoid Glucosides; D039823:Iridoids / Q000032:analysis / Q000737:chemistry; D010626:Phenylethyl Alcohol / Q000031:analogs & derivatives / Q000032:analysis / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization / Q000295:instrumentation / Q000379:methods*; D013594:Syringes
chemical_list: D057888:Iridoid Glucosides; D039823:Iridoids; C005975:3,4-dihydroxyphenylethanol; C002769:oleuropein; D010626:Phenylethyl Alcohol
keywords: DOE; Design of experiments; Hydroxytyrosol; LTQ-orbitrap; Oleuropein; Signal intensity