title: Challenges in developing an ultra-sensitive bioanalytical method for ethinylestradiol in human plasma.
abstract: BACKGROUND
  Ethinylestradiol (EE) is the active component in most birth control products. It is especially difficult to analyze due to the presence of many closely related endogenous steroids. Endogenous components can coelute with EE making selective extraction and chromatographic separation challenging. Current MS systems are more sensitive to background, contamination and the overall cleanliness of samples and solvents, placing additional emphasis on sample preparation methodology.
  
  
  METHODS
  UPLC was combined with a sensitive triple quadrupole MS and a three-step sample preparation method to highlight and resolve method development challenges.
  
  
  RESULTS
  EE was adequately resolved using an unendcapped high-strength silica C(18) column. The average matrix factor in six sources of plasma was 1.14 with a %CV of 4.48. Standard curves were linear with 1/x weighting and r(2) value of 0.999 over three orders of magnitude. Average accuracy for standard curves and quality control samples was 96%. LOD of 0.001 ng/ml was achieved.
authors.affiliation: Waters Technologies Corporation, Chemistry Applied Technology, Milford, MA 01757, USA.
authors.forename: Jessalynn P
authors.initials: JP
authors.lastname: Wheaton
authors.forename: Erin E
authors.initials: EE
authors.lastname: Chambers
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Fountain
mesh_terms: D053000:Analytic Sample Preparation Methods; D001774:Blood Chemical Analysis / Q000379:methods*; D002851:Chromatography, High Pressure Liquid; D004355:Drug Stability; D004967:Estrogens / Q000097:blood* / Q000737:chemistry / Q000302:isolation & purification; D004997:Ethinyl Estradiol / Q000097:blood* / Q000737:chemistry / Q000302:isolation & purification; D005260:Female; D006801:Humans; D059625:Liquid-Liquid Extraction; D015203:Reproducibility of Results; D053719:Tandem Mass Spectrometry
chemical_list: D004967:Estrogens; D004997:Ethinyl Estradiol