Determination of Oxygen Permeability/Transmissibility and Storage of Contact Lenses Using HPLC with Reductive Electrochemical Detection in Combination with a Specifically Designed Sampling Unit

Abstract

A new analytical technique for the determination of oxygen permeability/transmissibility of contact lenses is presented in this paper. The method is based on high performance liquid chromatography (HPLC) with reductive electrochemical detection at -750 mV (vs Ag/AgCl) in combination with a patented sampling chamber that was designed especially for the purpose to determine oxygen at nanomolar levels. Compared to conventional method, the new technique exhibits higher sensitivity, selectivity, and versatility. The method permits the selective determination of oxygen permeability (Dk/L)/transmissibility (Dk) of soft as well as rigid contact lenses with good agreement with the Dk/L (Dk) values reported in the literature. Precision was determined by repeated measurements and yielded relative standard deviations of 3-8% for hydrophile lenses and 5-13% for rigid contact lenses. Because of the extraordinarily high sensitivity of the chromatographic oxygen sensor for the first time, the capability of hydrogel lenses to store oxygen could also be directly monitored.

Water‐swollen highly oxygen permeable membranes: Analytical technique and syntheses

“…The sensitive amperometric detector is capable of detecting oxygen at nanometer levels. The reproducibility and the reported error for both low and high oxygen permeability contact lenses were quite low (6–10%); however, the values for the high Dk lenses were 20–30% off the values claimed by the manufacturers and other researchers 7. According to the authors, steady‐state conditions are not needed for accurate measurements; nonetheless, the equations they used presume such conditions.…”

“…Since the introduction of modern silicon‐based hydrogels for extended‐wear soft contact lenses in 1997, several attempts have been made to develop techniques for the measurement of oxygen permeabilities above the ∼100‐barrer limit. Thus, Obendorf and Wilhelm7 developed a methodology in which the oxygen permeability of water‐swollen soft contact lenses placed between two diffusion chambers is determined by the use of a chromatographic oxygen sensor. The detector used for the determination of oxygen concentration is part of a high‐performance liquid chromatography (HPLC) system and samples are taken from the diffusion chambers and injected into the HPLC.…”

Electroanalytical Assessment of the Oxygen Permeability at the Gas‐Solid‐Liquid Interface in Polymer‐based Materials for Lens Applications

“…On the basis on the profile of the LSV in the absence and presence of oxygen, different electrode potentials were probed but the above value of −0.75 V vs Ag/AgCl was the best compromise. Similar value was previously used [6f,g,18] . The measurements were performed at interval times to monitor the oxygen concentration as a function of time.…”

Contact Lens Technology: From Fundamentals to Applications

“…Ideal properties for a contact lens material are durability, stability, clarity of vision, and the ability to preserve corneal metabolism by allowing a sufficient oxygen flow to the cornea . Properties of contact lenses may be grouped in mechanical, optical, and chemical.…”