β-blockers are active pharmaceutical compounds used for treating heart arrhythmia, as a precaution against heart failure, and as well for treating hypertension. As part of my master's degree thesis I developed a GC-MS method for determination of β-blockers. Sample preparation is based on solid-phase extraction without any derivatization needed. It includes a comparison of different solid-phase extraction cartridges. Solutions in concentration of 50 mg/L were used for preliminary analyses. Pharmaceutical tablets, containing different beta blockers (atenolol, bisoprolol, carvedilol, metoprolol, and propranolol), were dissolved in acetonitrile. Standard solutions in acetonitrile (bisoprolol, metoprolol and propranolol) for calibration curves (5–25 mg/L) were prepared from solid standards, based on the results of preliminary analyses. Analytes were determined either unchanged or as adducts, and mass spectrometry was used in both modes, using total ion current and selected-ion monitoring as well. During solid-phase extraciton method optimization, different cartridges were used (LC-18, DSC-18, OASIS HLB, X-C, and X-CW), also aqueous solutions of beta blockers with different pH or added NaCl, were used to compare the solid-phase extraction recovery. Method development began with standard solutions of beta blockers (in acetonitrile) and was then applied on urine samples (0.15; 0,2 and 0.4 mg/L). New calibration curves (5–25 mg/L), were prepared by using urine extract as solvent. Additionally, breakthrough volume, repeatability, and suitability of different calibration approaches (beta blockers in acetonitrile or urine extract) for urine samples was also tested. This method was successfully used to determine bisoprolol, metoprolol, and propranolol, in concentraction at least 0.2 mg/L. The following best extraction recoveries were calculated from the determination in TIC mode: (85.0 ± 2.4) % for metoprolol, (90.1 ± 6.0) % for propranolol, and (59.4 ± 8.3) % for bisoprolol.
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