title: Selective on-line trace enrichment for the determination of ethynyl steroids in urine by liquid chromatography with precolumn technology.
mesh_terms: D055598:Chemical Phenomena; D002621:Chemistry; D002851:Chromatography, High Pressure Liquid; D004997:Ethinyl Estradiol / Q000652:urine*; D006801:Humans; D009640:Norethindrone / Q000652:urine*; D009644:Norgestrel / Q000652:urine*; D013056:Spectrophotometry, Ultraviolet
chemical_list: D009644:Norgestrel; D004997:Ethinyl Estradiol; D009640:Norethindrone