Determination of association constants of inclusion complexes of steroid hormones and cyclodextrins from their electrophoretic mobility

CE estimation of the association constants of several steroid hormones with β-CD and γ-CD and their hydroxypropyl derivative is presented. Estriol, 17β-estradiol, ethynylestradiol, estrone, progesterone, mestranol and norethindrone are among the target analytes. The calculation of the cyclodextrin:analyte association constants were performed from the electrophoretic mobility values of steroids at different concentration of CDs in the run buffer. The reliability of the final data was ensured by employing three different linearisation plots (double reciprocal fit, Y-reciprocal fit and X-reciprocal fit). The highest inclusion affinity of target analytes was observed towards γ-CD and its hydroxypropyl derivative, which is demonstrated by high association constant values and corresponding good linearity of the plots. The affinity of steroids towards a particular CD type based on physical and structural characteristics is explored.