Determination of Norethindrone Stability on Red Delicious Apples

A stability‐indicating assay procedure for the determination of norethindrone on the surface of Red Delicious apple slices was developed. The apple slice is homogenized in pH 10 borate buffer solution and norethindrone is then partitioned into chloroform using a diffusion chamber that has a membrane that is permeable to hydrophobic compounds separating the buffer and chloroform. An aliquot of the chloroform extract is then evaporated to dryness and reconstituted in tetrahydrofuran. The reconstituted sample is then chromatographed on a C18 reversed‐phase column using a mobile phase consisting of water:tetrahydrofuran:methanol (63:26:11, v/v/v). Detection is in the UV range at 254nm. The chromatographic system is specific for norethindrone in the presence of its autoxidation products. Stability data indicate that norethindrone is stable for up to 6h on the surface of Red Delicious apples.