RP-HPLC chromatograms for IMD (3), its degradation products (1, 2), and IS (4) stored at: a RH ∼76.4%, b RH ∼50.9%, c RH ∼25.0%, d RH ∼0%; retention times: IMD tR = 5 min, degradation products tR ∼ 3/2 min (in chromatogram “d,” tR = 3 min), IS tR = 8 min