title: In vitro evaluation of lipids adsorbed on silicone hydrogel contact lenses using a new gas chromatography/mass spectrometry analytical method.
abstract: OBJECTIVE
  To establish a new analytical method using gas chromatography/mass spectrometry (GC/MS) for evaluating the lipids adsorbed on silicone hydrogel (SH) contact lenses: cholesterol, cholesterol ester, wax, and squalene.
  
  
  METHODS
  A novel GC/MS method was developed and validated for the repeatability, specificity, linearity, detection and quantitation limits, and percentage recovery. The lipids in an artificial tear solution were adsorbed on 5 SH lenses (asmofilcon A, balafilcon A, galyfilcon A, lotrafilcon A, and lotrafilcon B) and 1 conventional hydrogel lens (etafilcon A) in vitro. The lipids adsorbed were then extracted and analyzed by the GC/MS method.
  
  
  RESULTS
  Repeatability of this analytical method was less than 2.2% deviation for all test lipids; however, the analytes were completely discriminated with sharp peak shapes, and identified specifically. The correlation coefficient showing linearity was at least 0.991 under 50 microg/mL of lipid concentration. Detection and quantitation limits were statistically 0.5 to 0.8 microg/mL and 1.4 to 2.5 microg/mL, respectively, for all analytes. Percentage recovery was estimated as approximately 80% for 3 microg/lens, 90% for 5 microg/lens, and almost 100% for larger amounts of lipids. Quantitatively, the lipids absorbed on contact lenses were lotrafilcon A = (near equal) lotrafilcon B = (near equal) etafilcon A < asmofilcon A < galyfilcon A = (near equal) balafilcon A with the value of 0.4 to 7.6 microg/lens. Lipid adsorption on SH lenses varied depending on the lipid components and lens surface properties.
  
  
  CONCLUSIONS
  The GC/MS method established in this study is excellent for the repeatability, specificity, linearity, detection and quantitation limits, and percentage recovery, and provides a novel highly sensitive and useful tool for evaluating lipids adsorbed on SH lenses.
authors.affiliation: Menicon Co, Ltd, Nagoya, Japan.
authors.forename: Miyoko
authors.initials: M
authors.lastname: Iwata
authors.forename: Sadanori
authors.initials: S
authors.lastname: Ohno
authors.forename: Tetsuji
authors.initials: T
authors.lastname: Kawai
authors.forename: Hideji
authors.initials: H
authors.lastname: Ichijima
authors.forename: H Dwight
authors.initials: HD
authors.lastname: Cavanagh
mesh_terms: D000042:Absorption; D003263:Contact Lenses, Hydrophilic; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D006801:Humans; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000737:chemistry*; D066298:In Vitro Techniques; D008055:Lipids / Q000032:analysis*; D015203:Reproducibility of Results; D020034:Silicone Gels / Q000737:chemistry*
chemical_list: D008055:Lipids; D020034:Silicone Gels; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate