title: Ultra sensitive quantitation of endogenous oxytocin in rat and human plasma using a two-dimensional liquid chromatography-tandem mass spectrometry assay.
abstract: Oxytocin (OT) is a neuropeptide with an extremely low endogenous level (low pg/ml) in human plasma. It is very challenging to develop a highly sensitive assay to measure endogenous OT, including radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA). Electrospray ionization (ESI) liquid chromatography-tandem mass spectrometry (LC-MS/MS) can provide high-throughput and selective methods for quantification of peptides in biological samples. A novel and highly sensitive two-dimensional LC-MS/MS (2D-LC-MS/MS) assay combining solid-phase extraction (SPE) has been developed and validated for the determination of endogenous OT in both human and rat plasma. The lower limit of quantification (LLOQ) was 1.00 pg/ml for human and 50.0 pg/ml for rat. Human plasma diluted with water (1:6, v/v) was successfully optimized as a surrogate matrix for human to prepare standard curves without endogenous interference. The extraction efficiency and absolute recovery were above 65.8% using the HLB SPE procedure, and matrix effects were lower than 12%. The method was validated in the range of 1.00-250 pg/ml for human plasma and 50.0-10,000 pg/ml for rat plasma with precision less than 12.7% and accuracy less than 7%.
authors: Biomarker Research, Pharmacokinetics, Dynamics, and Metabolism, Pfizer Global Research and Development, Pfizer, Groton, CT 06340, USA. guodong.zhang@pfizer.com
authors: Guodong
authors: G
authors: Zhang
authors: Yizhong
authors: Y
authors: Zhang
authors: Douglas M
authors: DM
authors: Fast
authors: Zhaosheng
authors: Z
authors: Lin
authors: Rick
authors: R
authors: Steenwyk