Stability of epidoxorubicin in solid state

The influence of temperature and relative air humidity on the stability of epidoxorubicin hydrochloride (EP) was investigated. The degradation of the substance studied was determined: (a) in dry air at 393 K, (b) at relative air humidity ∼76% at 333 K, 343 K, 353 K, 363 K and 373 K, (c) in the relative air humidity range 50-90% at 363 K. The degradation of EP in the atmosphere of increased relative air humidity was a first-order reaction relative to substance concentration and in dry, hot air (RH 0%; 393 K) is a reversible first-order reaction relative to substance concentration. The dependences ln k = f(1/T) and ln k = f(RH%) were described by the equation: ln k = (35.1 ± 10.9) − (16,250 ± 3823)(1/T) and ln k = (3.79 ± 3.34) × 10−2 (RH%) − (12.9 ± 2.4), respectively. The kinetic and thermodynamic parameters of EP degradation were calculated. The parameters of separation were following: LiChrospher RP-18 column, 5 μm, 250 mm × 4 mm; mobile phase: the mixture of equal volume of acetonitrile and the solution containing 2.88 g l−1 of sodium laurisulfate and 2.25 ml l−1 of phosphoric acid (V) 85%; flow rate: 1.0 ml min−1; UV detection - 254 nm.