Assay of free captopril in human plasma as monobromobimane derivative, using RPLC/(+)ESI/MS/MS: validation aspects and bioequivalence evaluation

Abstract

A sensitive method for determination of free captopril as monobromobimane derivative in plasma samples is discussed. The internal standard (IS) was 5-methoxy-1H-benzimidazole-2-thiol. Derivatization with monobromobimane immediately after blood collection and plasma preparation prevents oxidation of captopril to the corresponding disulfide compound and enhances the ionization yield. Consequently, derivatization enhances sample stability and detection sensitivity. Addition of the internal standard was made immediately after plasma preparation. The internal standard was also derivatized by monobromobimane, as it contains a thiol functional group. Preparation of plasma samples containing captopril and IS derivatives was based upon protein precipitation through addition of acetonitrile, in a volumetric ratio 1:2. The reversed-phase liquid chromatographic separation was achieved on a rapid resolution cartridge Zorbax SB-C(18), monitored through positive electrospray ionization and tandem MS detection using the multiple-reaction monitoring mode. Transitions were 408-362 amu for the captopril derivative and 371-260 amu for the internal standard derivative. The kinetics of captopril oxidation to the corresponding disulfide compound in plasma matrix was also studied using the proposed method. A linear log-log calibration was obtained over the concentration interval 2.5-750 ng/mL. A low limit of quantitation in the 2.5 ng/mL range was obtained. The analytical method was fully validated and successfully applied in a three-way, three-period, single-dose (50 mg), block-randomized bioequivalence study for two pharmaceutical formulations (captopril LPH 25 and 50 mg) against the comparator Capoten 50 mg.

Review of in situ derivatization techniques for enhanced bioanalysis using liquid chromatography with mass spectrometry

“…This method was able to achieve a good mean recovery of 99.9% and a LOQ of 10 ng/mL. Monobromobimane was also used for the ISD of captopril in human plasma to stabilize captopril and to improve its ionization yield . A mean recovery of 96% and a LOQ of 2.5 ng/mL were achieved.…”

Sample preparation for large‐scale bioanalytical studies based on liquid chromatographic techniques

“…Basically, a derivatization procedure is intended to improve at least one of the principal analytical parameters, namely the detection sensitivity or separation selectivity by modifying hydrophobic/hydrophilic character of target species. Other purposes of derivatization for HPLC analysis can be (a) increasing the stability of the target compounds (Medvedovici, Albu, et al, ); (b) obtaining more information for compound identification; (c) increasing recoveries by means of a full accordance between structural properties and proposed isolation methods; and (d) enhancing the selectivity of the SP procedure acting on the matrix components (Medvedovici, Farca, & David, ). The choice of the derivatization reaction depends on several process parameters, such as functional groups(s) contained in the molecules of target compounds, the concentration of these analytes, the complexity of the sample matrix, the detection mode, and the number of produced derivatization artifacts (Moldoveanu & David, ).…”

Separation methods for captopril in pharmaceuticals and biological fluids

“…Medvedovici et al [] used MBB as a derivatizing agent to increase the ionization yield besides enhancing the drug stability. Acetonitrile–aqueous 0.2% formic acid (15:85, v/v) was used in the isocratic mode as a mobile phase at 60 ○ C. Positive ESI and tandem MS detection using the multiple‐reaction monitoring mode were employed to give a LOQ of 2.5 ng/mL.…”