A titration method for quick and safe purification of solvents and monomers for anionic polymerization of styrene and dienes is presented. Protic impurities in the reaction-medium are removed by titration with butyllithium. The coloured carbanion of 4,5-methylenephenanthrene is used as an indicator to determine the end point of the titration. The titration is used in the synthesis of homopolymers and block copolymers of styrene and dienes with variable 1,2-polydiene content. Homopolymers and block copolymers in a large range of composition, molecular weight and with narrow molecular weight distribution were synthetized using the titration.