title: Improving quantitative gas chromatography-electron ionization mass spectrometry results using a modified ion source: demonstration for a pharmaceutical application.
abstract: Gas chromatography-mass spectrometry is a well established analytical technique. However, mass spectrometers with electron ionization sources may suffer from signal drifts, hereby negatively influencing quantitative performance. To demonstrate this phenomenon for a real application, a static headspace-gas chromatography method in combination with electron ionization-quadrupole mass spectrometry was optimized for the determination of residual dichloromethane in coronary stent coatings. Validating the method, the quantitative performance of an original stainless steel ion source was compared to that of a modified ion source. Ion source modification included the application of a gold coating on the repeller and exit plate. Several validation aspects such as limit of detection, limit of quantification, linearity and precision were evaluated using both ion sources. It was found that, as expected, the stainless steel ion source suffered from signal drift. As a consequence, non-linearity and high RSD values for repeated analyses were obtained. An additional experiment was performed to check whether an internal standard compound would lead to better results. It was found that the signal drift patterns of the analyte and internal standard were different, consequently leading to high RSD values for the response factor. With the modified ion source however, a more stable signal was observed resulting in acceptable linearity and precision. Moreover, it was also found that sensitivity improved compared to the stainless steel ion source. Finally, the optimized method with the modified ion source was applied to determine residual dichloromethane in the coating of coronary stents. The solvent was detected but found to be below the limit of quantification.
authors.affiliation: Laboratory for Pharmaceutical Analysis, Faculty of Pharmaceutical Sciences, Katholieke Universiteit Leuven, Leuven, Belgium.
authors.forename: Ward
authors.initials: W
authors.lastname: D'Autry
authors.forename: Kris
authors.initials: K
authors.lastname: Wolfs
authors.forename: Jos
authors.initials: J
authors.lastname: Hoogmartens
authors.forename: Erwin
authors.initials: E
authors.lastname: Adams
authors.forename: Ann
authors.initials: A
authors.lastname: Van Schepdael
mesh_terms: D002725:Chloroform / Q000737:chemistry; D054855:Drug-Eluting Stents; D008401:Gas Chromatography-Mass Spectrometry / Q000295:instrumentation* / Q000379:methods; D016014:Linear Models; D008752:Methylene Chloride / Q000032:analysis*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013193:Stainless Steel
chemical_list: D013193:Stainless Steel; D008752:Methylene Chloride; D002725:Chloroform