Measurement of brimonidine concentrations in human plasma by a highly sensitive gas chromatography/mass spectrometric assay |
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| Institution: | 1. The Retina Group of Washington, Chevy Chase, Maryland;2. Department of Ophthalmology, Georgetown University Hospital, Washington, DC;1. School of Life Sciences and Technology, Tongji University, 1239 Siping Road, Shanghai 200092, PR China;2. College of Grain Science and Technology, Shenyang Normal University, Shenyang, China;3. Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, PR China;4. Chuzhou University, School of Biology and Food Engineering, Chuzhou, Anhui 239000, PR China;1. School of Electrical Engineering & Computer Science, Seoul National University, Republic of Korea;2. Department of Chemistry Education, Seoul National University, Republic of Korea;3. School of Chemical & Biological Engineering, Institute of Chemical Processes, Seoul National University, Seoul 08826, Republic of Korea;4. Department of Bioscience and Biotechnology, Konkuk University, Seoul 05029, Republic of Korea;5. Division of Science Education, Kangwon National University, Chuncheon 24341, Republic of Korea |
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| Abstract: | Brimonidine is an α2-adrenergic agonist that is efficacious in lowering intraocular pressure in humans. A highly sensitive and selective gas chromatography/mass spectrometry (GC/MS) assay is described for quantitation of brimonidine in human plasma following ocular installation. Brimonidine in 1 ml of plasma was extracted together with tetradeuterated brimonidine (internal standard) and clonidine (carrier) by solvent extraction. After solvent evaporation, 3,5-bis(trifluoromethyl)benzoyl derivatives were formed and injected onto a GC/MS appartus under negative chemical ionization conditions. The ions monitored for derivatized brimonidine and tetradeuterated brimonidine were m/z 691 M - HBr] and m/z 694 M - DBr], respectively. Calibration curves were linear from 2 to 1000 pg ml−1 (r2 = 0.981-0.996). The method was specific for brimonidine relative to endogenous compounds in plasma. The inter-day relative standard deviation for analysis of quality controls was 12% or less, and the inter-day assay accuracy ranged from 97 to 104% of nominals. The GC/MS assay showed adequate sensitivity for analysis of human samples from volunteers ocularly dosed with 0.5% brimonidine tartrate solution. Overall, the GC/MS assay showed excellent precision and accuracy, and a minimum quantifiable concentration of 2 pg ml−1. |
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