German Sergey Viktorovich RussiaSaratovSaratov State University , 83, Astrakhanskaya str., Saratov, 410012, Russia german0709@rambler.ru Author's articles ШИРОКОПОЛОСНЫЕ ПРОСВЕТЛЯЮЩИЕ ПОКРЫТИЯ НА ОСНОВЕ АМОРФНОГО ДИОКСИДА КРЕМНИЯ ДЛЯ СТЕКОЛ Synthesis of Monodisperse Magnetite: The Effect of Temperature, Sodium Hydroxide and Citric Acid Concentrations on the Size of Nanoparticles Sorption-fluorimetric Determination of Enrofloxacin with Magnetite Nanoparticles Modified by Polyethylenimine