Solid-Phase Extraction Combined with High Performance Liquid Chromatography-Diode Array Detector for Rapid Determination of Estrogens in Milk

Purpose: To develop a simple but effective method for the quantitative analysis of estrogens in milk.
Methods: Solid-phase extraction method was employed for the extraction of the estrogen from milk and high performance liquid chromatography-diode array detector (HPLC-DAD) was used for the determination of estrogen.
Results: Optimal chromatographic conditions were achieved on an Eclipse XDB-C18 column at a flow rate of 0.8 mL/min at room temperature. The products were monitored using a DAD detector set at 280 nm. The retention time of the three main estrogens were 15 min with a gradient program of acetonitrile/water, from 0 to 3 min, holding 35 % acetonitrile; from 4 to 7 min, ramped to 55 % acetonitrile; from 8 to 20 min, maintained at 55 % acetonitrile. The results showed that the calibration curve had good linearity within the concentration range of 0.5 - 8.0 μg/mL with correlation coefficient (R²) in the range of 0.9929-0.9936. The limit of detection was in the range of 0.025 - 0.045 μg/mL while mean recovery of estrogen from milk samples varied from 92.6 to 104.1 %. Satisfactory precision was obtained both for intra-assay (RSD, 1.8 to 4.4 %) and inter-assay (RSD, 2.0 to 4.7 %).
Conclusion: The proposed method is environmentally friendly, inexpensive and convenient, and should be helpful in analyzing estrogens in biological, environmental and food samples.

Keywords
Solid-phase extraction; Milk; Estrogens; High performance liquid chromatography-diode array detector