Chemometrics in pharmaceutical analysis

Application of a novel combination of near-infrared spectroscopy and a humidity-controlled 96-well plate to the characterization of the polymorphism of imidafenacin

Objectives

This study aimed to apply a currently available chemometric near-infrared spectroscopy technique to the characterization of the polymorphic properties of drug candidates. The technique requires only small quantities of samples and is therefore applicable to drugs in the early stages of development.

Methods

The combination of near-infrared spectroscopy and a patented 96-well plate divided into 32 individual, humidity-controlled, three-well compartments was used in the characterization of a hygroscopic drug, imidafenacin, which has two polymorphs and one pseudo-polymorph. Characterization was also conducted with powder X-ray diffraction and thermal analysis. The results were compared with those from routinely used conventional analyses.

Key findings

Both the microanalysis and conventional analysis successfully characterised the substance (transformation and relative stability among the two polymorphs and a pseudo-polymorph) depending on the storage conditions. Near-infrared spectroscopic analyses utilizing a humidity-controlled 96-well plate required only small amounts of the sample for characterization under the various conditions of relative humidity.

Conclusions

Near-infrared microanalysis can be applied to polymorphic studies of small quantities of a drug candidate. The results also suggest that the method will predict the behaviors of a hygroscopic candidate in solid pharmaceutical preparations at the early stages of drug development.

Comparative determination of polymorphs of indomethacin in powders and tablets by chemometrical near-infrared spectroscopy and x-ray powder diffractometry

The purpose of this research was to develop a rapid chemometrical method based on near-infrared (NIR) spectroscopy to determine indomethacin (IMC) polymorphic content in mixed pharmaceutical powder and tablets. Mixed powder samples with known polymorphic contents of forms alpha and gamma were obtained from physical mixing of 50% of IMC standard polymorphic sample and 50% of excipient mixed powder sample consisting of lactose, corn starch, and hydroxypropylcellulose. The tablets were obtained by compressing the mixed powder at 245 MPa. X-ray powder diffraction profiles and NIR spectra were recorded for 6 kinds of standard materials with various polymorphic contents. The principal component regression analysis was performed based on normalized NIR spectra sets of mixed powder standard samples and tablets. The relationships between the actual and predicted polymorphic contents of form g in the mixed powder measured using x-ray powder diffraction and NIR spectroscopy show a straight line with a slope of 0.960 and 0.995, and correlation coefficient constants of 0.970 and 0.993, respectively. The predicted content values of unknown samples by x-ray powder diffraction and NIR spectroscopy were reproducible and in close agreement, but those by NIR spectroscopy had smaller SDs than those by x-ray powder diffraction. The results suggest that NIR spectroscopy provides a more accurate quantitative analysis of polymorphic content in pharmaceutical mixed powder and tablets than does conventional x-ray powder diffractometry.