Development of an orthogonal method for mometasone furoate impurity analysis using supercritical fluid chromatography.

While supercritical fluid chromatography (SFC) has received great popularity in chiral separation and purification, it has rarely been used for trace level pharmaceutical impurity analysis, partially due to the limitation of instrument sensitivity. In this study, a packed column SFC method has been developed for the quantitative analysis of mometasone furoate and its trace level impurities. The UV detection was optimized to improve the sensitivity by 2-4 fold. In combination with an increased sample concentration, this SFC method is capable of trace level (0.05% of the active) analysis of the impurities. The SFC method used a silica column and a mobile phase consisting of CO(2) and methanol. The new method provides an orthogonal selectivity complementary to the reversed phase HPLC (RP-HPLC) method. All of the impurities and the active were baseline separated within 12 min on SFC, which is less than one third of the RP-HPLC method run time. The method was also partially validated for linearity, accuracy, precision (repeatability), and limit of quantitation. This study demonstrated that the SFC method, with improved sensitivity, can be a valuable tool to provide orthogonal selectivity for trace level impurity separation. With further validation, the method may be suitable for release testing and stability testing for mometasone furoate drug substance.