Determination of levonorgestrel and ethinyl estradiol in pharmaceutical formulations by H-point standard addi-tion method in nonaqueous solvent using simultaneous addition of both analytes

H-point standard addition method (HPSAM) with simultaneous addition of both analytes in nonaqueous solution was applied for determination of levonorgestrel (LEV) and ethinyl estradiol (EE) in LD and HD tablets. The results showed that, simultaneous determination could be performed with the ratio 1 to 5 of LEV-EE. The LOD for LEV and EE were obtained 5.1×10-7 and 9.6×10-7 M, respectively, and the corresponding values of %RSD (n=4) for LEV and EE were 1.96 and 2.69, respectively. Underworking conditions, the proposed method was successfully applied for simultaneous determination of LEV and EE in several synthetic mixtures and LD and HD tablets. *