Liquid chromatography-electrospray mass spectrometry (LC-MS) method for determination of esmolol concentration in human plasma

Analysis of 27 β-Blockers and Metabolites in Milk Powder by High Performance Liquid Chromatography Coupled to Quadrupole Orbitrap High-Resolution Mass Spectrometry

This paper presents an application of high performance liquid chromatography coupled with quadrupole orbitrap high-resolution mass spectrometry (HPLC-Q-Orbitrap HRMS) for the analysis of 27 β-blockers and metabolites in milk powder. Homogenized milk power samples were extracted by acetonitrile and purified by using Oasis PRiME HLB solid-phase extraction cartridges. The Ascentis^® C8 chromatographic column was used to separate the analytes. The quantification was achieved by using matrix-matched standard calibration curves with carazolol-d₇ and propranolol-d₇ as the internal standards. The results show an exceptional linear relationship with the concentrations of analytes over wide concentration ranges (0.5–500 μg kg⁻¹) as all the fitting coefficients of determination r² are > 0.995. All the limits of detection (LODs) and quantitation (LOQs) values were within the respective range of 0.2–1.5 μg kg⁻¹ and 0.5–5.0 μg kg⁻¹. Overall average recoveries were able to reach 66.1–100.4% with the intra- and inter-day variability under 10%. This method has been successfully applied to the screening of β-blockers and metabolites in commercial milk powders. At the same time, the corresponding characteristic fragmentation behavior of the 27 compounds was explored. The characteristic product ions were determined and applied to the actual samples screening.

Determination of BAPTA-AM, the acetoxymethyl tetraester of BAPTA, in rat plasma by liquid chromatography tandem mass spectrometry

BAPTA-AM is the acetoxymethylester of the calcium chelator BAPTA and has demonstrated efficacy in several animal models of cerebral ischemia. This paper describes the development of a method for the determination of BAPTA-AM in rat plasma by liquid chromatography/tandem mass spectrometry. Owing to multiple ester groups in the structure of BAPTA-AM, [M + Na](+) was chosen as the analytical ion for quantification of BAPTA-AM. During the analytical method development, a high percentage of organic solvent and the addition of an amount of sodium acetate and formic acid in the mobile phase were found to favor the sensitivity and reproducibility of [M + Na](+). Poor fragmentation was usually observed in the MS/MS spectra of sodium adduct ions. However, abundant and reproducible fragment ions were observed for the BAPTA-AM sodium adduct ion, and therefore the traditional selective reaction-monitoring mode was used to further improve the sensitivity of MS detection. Because of the lability of the ester bond, a combination of fluoride and hydrochloric acid was applied to minimize the enzymatic hydrolysis, and acetonitrile was chosen to avoid the chemical hydrolysis or solvolysis during the sample collection and preparation procedure. On the basis of these studies, a rapid, sensitive and reproducible method for the determination of BAPTA-AM in rat plasma, using LC/ESI-MS/MS and a simple protein precipitation procedure, was developed and validated. Also, the present method was successfully applied to the determination of BAPTA-AM plasma concentrations for pharmacokinetic studies in rats.

The pharmacokinetics of esmolol in pediatric subjects with supraventricular arrhythmias

Esmolol is often used in the acute management of children with arrhythmias and/or hypertension; however, pharmacokinetic studies of the drug in children have been limited. The objective of this study was to determine the pharmacokinetics of esmolol in children with a history of supraventricular arrhythmias (SVT) who were scheduled for diagnostic electrophysiology study or a catheter ablation procedure. Subjects were stratified into two age groups: 2-11 and 12-16 years. After an episode of stimulated or spontaneous SVT, esmolol was administered intravenously as a 1,000 microg/kg bolus followed by continuous infusion at 300 microg/kg/min. Blood samples were collected before, at 5, 10 and 15 min after the loading dose, and 3, 6, 9, 12, 15 and 20 min after the end of the infusion. Plasma concentration of esmolol was quantitated by a specific LC/MS assay. Pharmacokinetic data were available for 25 subjects. Arterial esmolol concentrations were approximately five times greater than venous concentrations. Esmolol had an extremely short distribution half-life (0.6 min), a rapid terminal elimination half-life (6.9 min), and a rapid clearance (119 +/- 51 mL/min/kg) which was not related to subject age or weight. Seventeen of the subjects (63%) converted to normal sinus rhythm in an average of 2 min (range 0-5 min). The pharmacokinetics of esmolol and its efficacy in terminating SVT in children is similar to that observed in adults.