Determination of Glucocorticoids using Cosurfactants Ultrasonic-Thermostatic-Assisted Cloud Point Extraction Followed by High Performance Liquid Chromatography

A novel approach, cosurfactants ultrasonic-thermostatic-assisted cloud point extraction (CUS-CPE) combined with high performance liquid chromatography and ultraviolet detection (HPLC-UV) is developed for the analysis of glucocorticoids (beclometasone dipropionate (BD), hydrocortisone butyrate (HB) and nandrolone phenylpropionate (NPP)) in human urine samples. In this study, four different cloud point extraction (CPE) systems are discussed, including DC-193-nonanoic acid, DC-193-sodium sulfate, DC-193-lauric acid and the classic Triton X-100 sulfate systems. Among them, DC-193-sodium sulfate and the classic Triton X-100 sulfate systems has been studied in the past few years. Comparing with the first two systems, DC-193-nonanoic acid system had a lower cloud point (CP), little UV absorbance and it is less damaging to the column of three glucocorticoids in same surfactant concentration which was required for application as a pre-concentration process prior to HPLC. Phase diagrams were used to study the cavitation and mass transfer behaviors of the two phases on micelles of polyether type organic silicon surfactant, PEG-12 dimethicone (DC-193). The volumes of surfactant-rich phase obtained were very small (the enrichment factor (EF) was 35), which was much smaller and had a quick phase separating speed than that of Triton X-100 in the same surfactant concentration. Linearity was investigated from 1 to 350 ng mL(-1). The limits of detection (LOD) thus estimated were 1.29 for BD, 2.67 for HB and 3.33 ng mL(-1) for NPP, respectively. In proposed CPE step is rapid and effective to obtain recovery of three glucocorticoids higher than 85%, which is similar or better than literature reported data. The method was shown to be selective, linear, precise and reproducible and successfully applied for the analysis of glucocorticoids in human urine samples.