1. A method of obtaining an alkylated cyclodextrin composition containing an alkylated cyclodextrin, comprising: (a) mixing a cyclodextrin with an alkylating agent to obtain a reaction medium containing an alkylated cyclodextrin, one or more undesirable components and one or more drug-degrading impurities； (b) conducting one or more separations with the removal of one or more undesirable components from the reaction medium to obtain a partially purified solution containing the specified alkyl anny cyclodextrin and said one or more impurities decomposing medicament, wherein said one or more separations are ultrafiltration, diafiltration, centrifugation, extraction, precipitation with solvent, Go dialysis； and (c) treating said partially purified solution with phosphate-free activated carbon having a residual conductivity of 10 μS or less and obtaining an alkylated cyclodextrin. 2. A method according to claim 1, characterized in that said alkylated cyclodextrin composition further comprises less than 500 ppm of phosphate. A method according to claim 1, characterized in that said alkyl cyclodextrin composition further comprises less than 125 ppm of phosphate. A method according to claim 1, characterized in that said residual conductivity in step (c) is 9 μS or less. The method of claim 1, wherein said residual conductivity in step (c) is 8 μS or less. A method according to claim 1, characterized in that said alkyl cyclodextrin composition further comprises less than 0.5% (w / w) chloride. The method according to claim 1, characterized in that the said1. Способ получения композиции алкилированного циклодекстрина, содержащей алкилированный циклодекстрин, включающий:(a) смешивание циклодекстрина с алкилирующим агентом с получением реакционной среды, содержащей алкилированный циклодекстрин, один или более нежелательных компонентов и одну или более примесей, разлагающих лекарственное средство；(b) проведение одного или более разделений с удалением одного или более нежелатель
