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

Esmolol is a very short-acting β-blocker commonly used in critically ill patients. To study the pharmacokinetics of esmolol in pediatric patients, a liquid chromatography–electrospray mass spectrometry (LC–MS) method to quantitate esmolol concentration in plasma was developed. Following methylene chloride extraction from 200 μl aliquots of plasma containing internal standard and reconstitution in 0.05% formic acid, 10 μl are injected onto column, eluted using a methanol/formic acid gradient over 15 min, and monitored with selected ion recording at 296.2 and 282.2. The assay is linear between 2 and 1000 ng/ml. The intra-day and inter-day coefficients of variation are less than 8 and 10%, respectively.