Determination of Estrogens in Milk Using Polypyrrole Fiber-Mediated Solid-Phase Extraction Followed by High Performance Liquid Chromatography

Abstract

A solid-phase extraction (SPE) method based on conductive polypyrrole (PPy) nanofibers which were fabricated by electrospinning and in situ polymerization was developed. PPy nanofibersmediated SPE followed by high performance liquid chromatography (HPLC) was used for the determination of three synthetic estrogens, namely diethylstilbestrol (DES), dienestrol (DIS), or hexestrol (HS) in milk sample. Extraction conditions including extraction nanofibers, donor solution pH and salt concentration were optimized. The target compounds were extracted from a 0.5 mL aqueous sample at pH 5.0 through PPy fibers, and then were eluted with 0.1 mL methanol. After extraction, the eluant was directly injected into an HPLC system for detection. Under the optimized extraction conditions, a large enrichment factor was achieved for three estrogens. The limit of detection (LOD) at a signal to noise ratio (S/N) of 3 ranged from 0.02 to 0.05 μg mL -1 for the estrogens in milk sample.Keywords: liquid dairy products, packed-fibers solid-phase extraction, high performance liquid chromatography, estrogens IntroductionEstrogens have been considered as one of the groups of analytes concerned in certain food matrices, especially in milk and other dairy products.1 Synthetic estrogens such as diethylstilbestrol (DES), dienestrol (DIS) and hexestrol (HS) are potent regulatory factors in physiological response medicine, and have been used widely as growth promoters in livestock and as a treatment for estrogen-deficiency disorders in veterinary medicine.A variety of techniques have been applied to determine estrogens. The abuse of estrogens is known to be strongly harmful to humans owing to their potential carcinogenic properties. The use of estrogens in food-producing animals and other products has been prohibited in many countries. Synchronously, more attention is paid to residue analysis of these estrogens that helps us control their illegal use.2-4 Generally, the determination of DES in wastewater has been carried out using gas chromatographymass spectrometry, 5,6 liquid chromatography-mass spectrometry 7,8 or high performance liquid chromatography equipped with diode array detection. [9][10][11] Since the concentration of DES in complex matrices is usually extremely low, a preconcentration step, such as solidphase extraction (SPE) and liquid-phase microextraction (LPME), is required. However, the lack of selectivity and low recovery are the main problems in the determination of estrogens by using common samples preconcentration. [12][13][14][15] Solid-phase extraction, because of its advantages such as less organic solvent consumption, simplicity, high recovery rate, easy operation and automation, has been Determination of Estrogens in Milk Using Polypyrrole Fiber-Mediated Solid-Phase Extraction J. Braz. Chem. Soc. 2138 widely applied to the extraction of different compounds. 16 Recently, a novel solid-phase extraction method based on electrospun polymer nanofibers as adsorbents to enrich target compounds has been developed. 17 Owing to t...