Fenofibrate raw materials: HPLC methods for assay and purity and an NMR method for purity

HPLC methods for drug content and HPLC and NMR methods for related compounds in fenofibrate raw materials were developed. The HPLC methods resolved 11 known and six unknown impurities from the drug. The HPLC system was comprised of a Waters Symmetry ODS column (100 x 4.6 mm, 3.5 microm), a mobile phase consisting of acetonitrile water trifluoroacetic acid 700/300/l (v/v/v) at a flow rate of 1 ml min(-1). and a UV detector set at 280 nm. Minimum quantifiable amounts were about 0.1% for three of the compounds and less than 0.05% for the other eight. Individual impurities in 14 raw materials ranged from trace levels to 0.25%, and total impurities from 0.04 to 0.53% (w/w). Six unknown impurities were detected by HPLC, all at levels below 0.10%, assuming the same relative response as fenofibrate. An NMR method for related compounds was also developed and it was suitable for 12 known and several unknown impurities. It requires an NMR of 400 MHz, or greater, field strength. Individual impurities in the raw materials analyzed ranged from trace levels to 0.24%, and total impurities from trace levels to 0.59%. Several lots contained small amounts of unknown impurities at trace levels. Three lots, all from the same manufacturer, contained an unknown impurity, not detectable by HPLC, which was not present in the other raw materials. It was estimated to be present at a level greater than 0.2%. The results for related compounds by the two techniques were consistent. The main differences stem from the low sensitivity of the HPLC method for some of the related compounds at 280 nm, or from the higher limits of quantitation by the NMR method for several other impurities using the conditions specified. A fifteenth raw material was not homogeneous in its content of impurity VI, a synthetic intermediate and possible degradation product. The HPLC/MS results provided information on the peak purity (number of components) for minor HPLC peaks, as well as structural data such as the molecular ions and diagnostic fragment ions. The HPLC/MS results showed that there were five unknown drug related impurities, for which there were no standards available. Results for the assay of 15 raw materials by HPLC were within the range 98.5-101.5%.