title: Stepwise injection potentiometric determination of caffeine in saliva using single-drop microextraction combined with solvent exchange.
abstract: A flow potentiometric method for determination of caffeine in saliva is suggested. This task is important for non-invasive assessment of drug metabolizing system activity in hepatocytes. In the current study, stepwise injection analysis (SWIA) was successfully combined with single-drop liquid microextraction (SDLME) and solvent exchange procedure. The method is based on the caffeine SDLME with subsequent solvent evaporation and dissolution of analyte in sulfuric acid followed by potentiometric detection using poly(vinyl chloride) membrane electrode containing potassium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate as electroactive component. SDLME was employed for elimination of interfering matrix effects of saliva and caffeine metabolites such as theophylline, theobromine and paraxanthine. A linear range of 10(-5)-10(-2)M was established for caffeine with detection limit at 6 × 10(-6)M. The sample throughput was 6 samples h(-1). The proposed method was successfully applied to the determination of caffeine in saliva and the analytical results agreed well with the results obtained with reference HPLC method.
authors.affiliation: Department of Analytical Chemistry, Institute of Chemistry, Saint-Petersburg University, St. Petersburg State University, SPbSU, SPbU, 7/9 Universitetskaya nab., St. Petersburg 199034, Russia. Electronic address: timofeeva.irina.7@gmail.com.
authors.forename: I
authors.initials: I
authors.lastname: Timofeeva
authors.affiliation: Department of Analytical Chemistry, Institute of Chemistry, Saint-Petersburg University, St. Petersburg State University, SPbSU, SPbU, 7/9 Universitetskaya nab., St. Petersburg 199034, Russia.
authors.forename: K
authors.initials: K
authors.lastname: Medinskaia
authors.affiliation: Department of Analytical Chemistry, Institute of Chemistry, Saint-Petersburg University, St. Petersburg State University, SPbSU, SPbU, 7/9 Universitetskaya nab., St. Petersburg 199034, Russia.
authors.forename: L
authors.initials: L
authors.lastname: Nikolaeva
authors.affiliation: Department of Analytical Chemistry, Institute of Chemistry, Saint-Petersburg University, St. Petersburg State University, SPbSU, SPbU, 7/9 Universitetskaya nab., St. Petersburg 199034, Russia.
authors.forename: D
authors.initials: D
authors.lastname: Kirsanov
authors.affiliation: Department of Analytical Chemistry, Institute of Chemistry, Saint-Petersburg University, St. Petersburg State University, SPbSU, SPbU, 7/9 Universitetskaya nab., St. Petersburg 199034, Russia.
authors.forename: A
authors.initials: A
authors.lastname: Bulatov
mesh_terms: D002110:Caffeine / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D057230:Limit of Detection; D059627:Liquid Phase Microextraction / Q000295:instrumentation*; D011199:Potentiometry / Q000379:methods*; D012463:Saliva / Q000737:chemistry*; D013805:Theobromine / Q000032:analysis; D013806:Theophylline / Q000032:analysis
chemical_list: D002110:Caffeine; D013806:Theophylline; D013805:Theobromine; C021183:1,7-dimethylxanthine
keywords: Caffeine; Caffeine sensor; Saliva; Single-drop liquid microextraction; Stepwise injection analysis