Stock standard solution containing Isotretinoin (150 µg
mL-1) and Erythromycin (6000 µg mL-1) was prepared by
dissolving 7.5 mg Isotretinoin and 300 mg Erythromycin
in methanol in a 50 mL volumetric flask. Working standard
solution of Isotretinoin and Erythromycin was prepared
at concentration of 15 ng µL-1 and 600 ng µL-1
respectively, by diluting the stock standard solution in
methanol. The stock solution was stored at 2-8°
C protected
from light.