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.