Microextraction by packed sorbent and liquid chromatography-tandem mass spectrometry as a tool for quantification of peptides in plasma samples: determination of sensory neuron-specific receptors agonist BAM8-22 and antagonist BAM22-8 in plasma samples.

Microextraction by packed sorbent (MEPS) is a miniaturized, solid-phase extraction (SPE) technique that works online with gas chromatography (GC) and liquid chromatography (LC). Not only is the automation process with MEPS advantageous, but the much smaller volumes of the samples, solvents and dead space in the system also provide other significant advantages such as the speed and the simplicity of the sample preparation process. In this study MEPS has been evaluated for quantification of sensory neuron-specific receptors agonist (BAM8-22). Owing to the instability of BAMs, the focus was on fast extraction and determination of the peptide online using LC-MS/MS. Sorbents such as C2, C8 and ENV+ (hydroxylated polystyrene-divinylbenzene copolymer) were investigated in the present study. MEPS-C8 gave the best results compared with C2 and ENV and it was used for the method validation. The calibration curve was obtained within the concentration range of 20.0-3045 nmol/L in plasma. The regression correlation coefficients for plasma samples were ≥ 0.99 for all runs (n = 6). The between-batch accuracy and precision for BAM8-22 ranged from -13 to -2.0% and from 4.0 to 14%, respectively. Additionally, the accuracy and precision for BAM22-8 ranged from -13 to 7.0% and from 3.0 to 12%, respectively. The present method was used for pharmacokinetic studies for BAMs in plasma samples.