In vitro study of the binding between chlorpyrfos and sex hormones using headspace solid-phase microextraction combined with high-performance liquid chromatography

Endocrine-disrupting chemicals are compounds that alter the normal functioning of the endocrine system. Organophosphorus insecticides, as chlorpyrifos (CPS), receive an increasing consideration as potential endocrine disrupters. Physiological estrogens, including estrone (E1), 17β-estradiol (E2), and diethylstilbestrol (DES) fluctuate with life stage, suggesting specific roles for them in biological and disease processes. There has been great interest in whether certain organophosphorus pesticides can affect the risk of breast cancer. An understanding of the interaction processes is the key to describe the fate of CPS in biological media. The objectives of this study were to evaluate total, bound, and freely dissolved amount of CPS in the presence of three estrogenic sex hormones (ESHs). In vitro experiments were conducted utilizing a headspace solid phase microextraction (HS-SPME) combined with high-performance liquid chromatography (HPLC) method. The obtained Scatchard plot based on the proposed SPME-HPLC method was employed to determine CPS-ESHs binding constant and the number of binding sites as well as binding percentage of each hormone to CPS. The number of binding sites per studied hormone molecule was 1.10, 1, and 0.81 for E1, E2, and DES, respectively. The obtained results confirmed that CPS bound to one class of binding sites on sex hormones.