Borexino, a real-time device for low energy neutrino spectroscopy, has completed the construction phase at the middle of 2006 in the Underground Laboratories at Gran Sasso, Italy. The detector has been filled with 1300 tons of highly purified scintillator and 2600 tons of ultrapure water as external shield and, since May 16th, 2007, is under data taking. The experimental goal, the direct ... [Show full abstract] measurement of flux of 7Be solar neutrinos of all flavour via neutrino-electron scattering in an ultrapure scintillator liquid, has been achieved and further measurements (PP, PeP, CNO neutrinos, geoneutrinos, supernova) are object of future results. The paper describes the purification methods adopted in Borexino, to achieve unique and unprecedented results on the scintillator purity. Requirements and purification methods will be reported.