title: Comparison of piracetam measured with HPLC-DAD, HPLC-ESI-MS, DIP-APCI-MS, and a newly developed and optimized DIP-ESI-MS.
abstract: The direct inlet probe-electrospray ionization (DIP-ESI) presented here was based on the direct inlet probe-atmospheric pressure chemical ionization (DIP-APCI) developed by our group. It was coupled to an ion trap mass spectrometer (MS) for the detection of more polar compounds such as degradation products from pharmaceuticals. First, the position of the ESI tip, the gas and solvent flow rates, as well as the gas temperature were optimized with the help of the statistic program Minitab® 17 and a caffeine standard. The ability to perform quantitative analyses was also tested by using different concentrations of caffeine and camphor. Calibration curves with a quadratic calibration regression of R (2) = 0.9997 and 0.9998 for caffeine and camphor, respectively, were obtained. The limit of detection of 2.5 and 1.7 ng per injection for caffeine and camphor were determined, respectively. Furthermore, a solution of piracetam was used to compare established analytical methods for this drug and its impurities such as HPLC-diode array detector (DAD) and HPLC-ESI-MS with the DIP-APCI and the developed DIP-ESI. With HPLC-DAD and 10 μg piracetam on column, no impurity could be detected. With HPLC-ESI-MS, two impurities (A and B) were identified with only 4.6 μg piracetam on column, while with DIP-ESI, an amount of 1.6 μg piracetam was sufficient. In the case of the DIP-ESI measurements, all detected impurities could be identified by MS/MS studies. Graphical Abstract Scheme of the DIP-ESI principle.
authors.affiliation: Applied Analytical Chemistry, University of Duisburg-Essen, Universitätsstr. 5, 45141, Essen, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Lenzen
authors.affiliation: Adler Apotheke, Hauptstr. 79, 51399, Burscheid, Germany.
authors.forename: Gottfried A
authors.initials: GA
authors.lastname: Winterfeld
authors.affiliation: Applied Analytical Chemistry, University of Duisburg-Essen, Universitätsstr. 5, 45141, Essen, Germany. oliver.schmitz@uni-due.de.
authors.forename: Oliver J
authors.initials: OJ
authors.lastname: Schmitz
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D010889:Piracetam / Q000032:analysis*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D053719:Tandem Mass Spectrometry / Q000379:methods
chemical_list: D010889:Piracetam
keywords: Ambient desorption ionization method; DIP-APCI; DIP-ESI; Direct inlet probe; Pharmaceuticals; Piracetam