Picogram-level detection of three ACE inhibitors via LC–MS/MS: Comparing BMP and UOSA54 derivatization methods

A sensitive liquid chromatography–mass spectrometric method was developed to determine three angiotensin-converting enzyme (ACE) inhibitors, enalapril (ENA), ramipril (RAM), and perindopril (PER) at picogram levels in rabbit plasma. The method employs two derivatization reagents: 3-bromomethyl-propyphenazone (BMP) and a hydrazonoyl chloride (UOSA54). These reagents significantly enhanced the detection sensitivity of the analytes, with response factors increasing by 7–114 orders of magnitude compared to underivatized compounds. The ACE inhibitors were extracted from plasma using liquid–liquid extraction and then derivatized with either BMP or UOSA54. The BMP-derivatized analytes were analyzed using positive electrospray ionization-MS (ESI-MS) mode, while the UOSA54-derivatized analytes were analyzed using negative ESI-MS mode. The method demonstrated excellent sensitivity, with limits of quantification ranging from 0.03 to 30 ng·mL −1 for BMP-derivatized analytes and 0.3 to 300.0 ng·mL −1 for UOSA54-derivatized analytes. The calibration curves were linear, spanning a wide range of concentrations, with correlation coefficients ( r 2 ) close to unity for all analytes. The extraction recovery of the developed method ranges from 88% to 100%, outperforming other extraction procedures. The method’s applicability was validated through pharmacokinetic studies in rabbits, where it successfully quantified ACE inhibitors over 24 h post-oral administration. Pharmacokinetic parameters revealed distinct profiles for each ACE inhibitor: ENA exhibited a C max of 45.2 ± 3.1 ng·mL −1 , T max of 0.5 h, and AUC 0–24h of 210 ± 15 ng·h·mL −1 ; RAM showed a C max of 62.5 ± 4.2 ng·mL −1 , T max of 1 h, and AUC 0–24h of 315 ± 20 ng·h·mL −1 ; PER displayed the highest C max (78.3 ± 5.6 ng·mL −1 ), longest T max (2 h), and largest AUC 0–24h (410 ± 25 ng·h·mL −1 ). This method represents a significant advancement in ACE inhibitor analysis, offering unparalleled sensitivity and reliability for pharmacokinetic studies and therapeutic monitoring of these important cardiovascular drugs.