DETECTION OF CRYSTAL POLYMORPHS OF NATEGLINIDE BY DSC

AIMTo establish the differential scanning calorimetric (DSC) methodology for controlling the crystal-type B form of nateglinide. METHODSAccurately weighed pure dried (P₂O₅ as desiccant for 4 h at 80℃ in vacuum) fine powder of crystal-type B and H of nateglinide were measured dQ/dT by DSC at heating rate of 10℃·min^-1 and temperature between 100℃ and 200℃ to calculate the enthalpy ΔH_B and ΔH_H. Accurately weigh a series of uniform mixtures of crystal-type B and H of dried fine powder of nateglinide in different proportions. The enthalpy of the mixtures is measured by DSC as above to calculate the enthalpy (ΣΔH). Using B% as X, ΣΔH as Y, the regression equation was obtained. According to this equation, the unknown composition of mixed crystal was evaluated by the ΣΔH values. The method was used to control the limitation of crystal-type B of nateglinide by the ΣΔH value of mixture of known composition as reference. RESULTSThe results measured from different laboratories showed that the repeatability was 0.61% and the recoveries were 86.2%～127% when the amounts of crystal-type B were between 0～15%.CONCLUSIONThis method can be used to evaluate the crystal-type B composition of nateglinide.