Abstract
A highly sensitive ultra high pressure liquid chromatography (UHPLC-MS/MS) method for estimation of ropinirole in rat brain homogenate and plasma has been validated. The method was successfully used for the degradation kinetics in different stress condition and regulated temperature. The chromatographic separation was achieved using isocratic mobile phase, consisting of acetonitrile-2mM ammoniumacetate (28:72 v/v; 0.25 mL min(-1)). The mass spectrometer was operated in synapt mass spectrometry mode via positive electrospray ionization using the transitions m/z 260 -> m/z 261 for ropinirole, and m/z 324.39 -> m/z 262.161 as a parent ion of escitalopram (IS). The assay for ropinirole was linear over the range of 0.5-100 ng mL(-1) (r(2); 0.999). The intra- and inter day precisions were less than 11.2% in terms of relative standard deviation (R.S.D.), and the accuracy was within +/- 6.4% in terms of relative error (RE). The mean extraction-efficiency of QC samples (MQC, 8 ng/mL) was >= 80%. The lower limit of quantification (LLOQ) was 0.049 ng/mL where as lower limit of detection (LLOD) was 0.016 ng/mL. All the peaks of degradation were well resolved. The degradation kinetics of ropinirole, showed highest stability (t(1/2) 256.66/h; t(0.9), 39.11/h) in acidic medium, lower stability in alkaline environment (t(1/2), 103.43/h; t(0.9), 15.76/h) and highly susceptible in oxidative environment (t(1/2), 21.58/h; t(0.9), 3.28/h). The applicability of this assay was demonstrated and successfully applied for pharmacokinetic profiling of ropinirole in Wister rat brain homogenate after intranasal administration.