Direct separation, identification and quantification of epimers 22R and 22S of budesonide by capillary gas chromatography on a short analytical column with Rtx-5 stationary phase.

The conditions for separation, identification and quantitative determination of epimers 22R and 22S of budesonide by capillary gas chromatography (GC) with FID detection and two various sample injection methods, namely split-splitless and cool on-column, were established. In analysis helium as carrier gas and Rtx-5 capillary column of 7 m in length along with stationary phase Crossbond 5% diphenyl-95% dimethyl polysiloxane were used. The individual epimers were identified under specified conditions by using standard samples of different declared concentration of each epimer under investigation: (1) 51.2% of epimer 22R and 47.3% of epimer 22S, and (2) 95.1% of 22R and 4.4% of 22S, as well as Pulmicort, a preparation containing micronized budesonide as an active substance. It seems that good parameters of preliminary validation achieved by the proposed methods can confirm its suitability for quantitative analysis purpose. The retention times obtained for epimers 22R and 22S, depending on injection technique are about 7.7 and. 8.3 min for split and, approx. 10.3 and 10.9 min for cool on-column. The limits of detection and quantitation are 5.7 and 6.2 ng, for 22R respectively, and 4.3 and 4.8 ng for 22S. The linearity is maintained for concentrations ranging from 0.01 to 0.20 mg/ml. The quantitative analysis features of repeatability, high precision and accuracy confirmed by the obtained results and its statistical evaluation.