Storage stable mixtures

A method of improving retention of a compound of formula (I):

• wherein
• n is an integer from 1 to 15,
• R1 is selected from the group consisting of H, C1-C6alkyl, phenyl, —OH, —NH2, —CN, —COOH, —O(C═O)R8, —NHC(═O)R8, SO2NHR8, and —ONO2, and
• R8 is C1-C6alkyl, phenyl, with the proviso that when n is >3 the hydrocarbon chain may be interrupted by —O—or —NH—
• in a powderous formulation comprising:
• (i) the compound according to formula (I), and
• (ii) silica, wherein
• the method comprises admixing the powderous formulation with a starch derived from potatoes, wheat, maize and/or cassava.