A rapid, simple and sensitive liquid chromatography-mass spectrometry (LC-MS) method was developed and validated for the determination of the imidazole H(3) antagonist ROS203 in rat plasma, using the superior homologue ROS287 as internal standard. Analyses were performed on an Agilent 1100 Series HPLC system employing a Supelco Ascentis C(18) column and isocratic elution with acetonitrile-10mM ammonium acetate buffer pH 4.0 (30:70, v/v) at a flow rate of 0.25 mL/min. An Applied Biosystems/MDS Sciex 150-EX single quadrupole mass spectrometer, equipped with an electrospray ionization interface was employed, operating in the positive ion mode. Plasma samples were deproteinized with acetonitrile (1:2), evaporated under nitrogen stream, reconstituted in the mobile phase and 5 microL were injected into the system. The retention times of ROS203 and IS were 2.20 and 2.90 min, respectively. Calibration curves in spiked plasma were linear over the concentration range of 2610-2.61 ng/mL with determination coefficients >0.99. The lower limit of quantification (LLOQ) was 2.61 ng/mL. The accuracy of the method was within 15%. Intra- and inter-day relative standard deviations were less or equal to 9.50% or 7.19%, respectively. The applicability of the LC-MS method was tested employing plasma samples obtained after i.p. administration of ROS203 to female Wistar rats to support a behavioral in vivo study. The specificity of the method was confirmed by the absence of interferences from endogenous substances. The reported method can provide the necessary sensitivity, linearity, precision, accuracy and specificity to allow the determination of ROS203 in rat plasma samples to support further pharmacokinetic assays.
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