title: Hollow-fiber liquid-phase microextraction for the determination of natural and synthetic estrogens in milk samples.
abstract: In this work, a group of nine estrogens, four of them being natural (estriol, 17β-estradiol, 17α-estradiol and estrone), four being synthetic (17α-ethynylestradiol, diethylstibestrol, dienestrol and hexestrol) and one metabolite (2-hydroxyestradiol) have been extracted and preconcentrated from milk samples with different fat content (whole, semi-skimmed and skimmed). After protein precipitation with acetonitrile containing acetic acid, evaporation of the supernatant and reconstitution of the residue in water, hollow-fiber liquid-phase microextraction (HF-LPME) using 1-octanol as extraction solvent was applied to further preconcentrate the analytes. Separation, determination and quantification were achieved by high-performance liquid chromatography coupled to a diode array detector and a fluorescence detector set in series. Deproteinization conditions, as well as parameters affecting the extraction efficiency in HF-LPME (pH of the sample, ionic strength, extraction time, stirring speed, temperature and desorption conditions) were investigated and optimized. Calibration, precision and accuracy studies were carried out to validate the methodology in different types of milk providing LODs in the low μg/L range.
authors.affiliation: Departamento de Química Analítica, Nutrición y Bromatología, Facultad de Química, Universidad de La Laguna (ULL), Avenida Astrofísico Francisco Sánchez s/n°, 38206 La Laguna (Tenerife), Spain.
authors.forename: Bárbara
authors.initials: B
authors.lastname: Socas-Rodríguez
authors.forename: María
authors.initials: M
authors.lastname: Asensio-Ramos
authors.forename: Javier
authors.initials: J
authors.lastname: Hernández-Borges
authors.forename: Miguel Ángel
authors.initials: MÁ
authors.lastname: Rodríguez-Delgado
mesh_terms: D000818:Animals; D002417:Cattle; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D045166:Estradiol Congeners / Q000032:analysis* / Q000737:chemistry / Q000302:isolation & purification; D004967:Estrogens / Q000032:analysis* / Q000737:chemistry / Q000302:isolation & purification; D006863:Hydrogen-Ion Concentration; D057230:Limit of Detection; D059627:Liquid Phase Microextraction / Q000379:methods*; D008892:Milk / Q000737:chemistry*; D009994:Osmolar Concentration; D015203:Reproducibility of Results; D013696:Temperature
chemical_list: D045166:Estradiol Congeners; D004967:Estrogens
keywords: Estrogens; High-performance liquid chromatography; Hollow-fiber liquid phase microextraction; Milk