Multiple reaction monitoring scan chromatograms of enalapril, enalaprilat, and benazepril. The left graph illustrates the shift in retention time detected by comparing the analytes solved in mobile phase versus the analytes in purified matrix during first extraction attempts. Right graph shows the final chromatogram by comparing also the analytes in mobile phase versus analytes in purified serum. A timely shift in retention time was not detectable anymore. MRMs: 377.2 → 234.2 m/z (enalapril), 349.1 → 206.1 m/z (enalaprilat), and 425.3 → 351.2 m/z (benazepril). The black line identifies the extracted serum samples and the grey line illustrates the drug substances dissolved in mobile phase. Cps: counts.
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