The invention relates to a method for treating a biological sample, comprising the following method steps: i) preparation of a biological sample and ii) bringing the biological sample into contact with a composition, comprising: (1) 1 to 100 wt. % of at least one polyol and (2) 0 to 99 wt. % of at least one additive, wherein the total amount of components (1) and (2) is 100 wt. %. The invention further relates to biological samples obtained by said method, a method for analysis of a treated biological sample, devices for treating a biological sample, use of said devices, various kits and use of a composition.