[Detection of crystal polymorphs of nateglinide by DSC]

To establish the differential scanning calorimetric (DSC) methodology for controlling the crystal-type B form of nateglinide.

Accurately weighed pure dried (P2O5 as desiccant for 4 h at 80 degrees C in vacuum) fine powder of crystal-type B and H of nateglinide were measured dQ/dT by DSC at heating rate of 10 degrees C. min-1 and temperature between 100 degrees C and 200 degrees C to calculate the enthalpy delta HB and delta HH. Accurately weight 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 (sigma delta H). Using B% as X, sigma delta H as Y, the regression equation was obtained. According to this equation, the unknown composition of mixed crystal was evaluated by the sigma delta H values. The method was used to control the limitation of crystal-type B of nateglinide by the sigma delta H value of mixture of known composition as reference.

The 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%.

This method can be used to evaluate the crystal-type B composition of nateglinide.