NEAR-INFRARED (NIR) MONITORING OF H2O2 VAPOR CONCENTRATION DURING VAPOR HYDROGEN-PEROXIDE (VHP) STERILIZATION

Purpose. There is an increasing use in the pharmaceutical industry of barrier systems such as transfer isolators, sterilisation tunnels and work station isolators. As Vapor Hydrogen Peroxide (VHP) sterilisation of isolators and lyophilizers becomes an important sterilisation meth od, there is an acute need for a VHP monitoring system to be used for in-process control and validation. In this study, near infrared (NIR) spectrofotometry was evaluated as a potential technique to monitor hyd rogen peroxide. Additionally the H2O2 vapor permeability of different packaging materials, commonly used in steam and ethylene oxide sterili sation, was evaluated. Methods. NIR spectrofotometry, using a gas cell connected with optic fibres, was evaluated as a potential technique t o monitor hydrogen peroxide vapor and water vapor during VHP sterilisa tion of an isolator. A NIR spectrum was taken every 30 s during VHP st erilisation of an isolator. The influence of injection rate, air flow rate, working temperature and gas distribution was investigated. The H 2O2 vapor permeability of different packaging materials was determined by placing the gas cell in the sterilisation bags and sealing the bag s hermetically. The sterilisation bag was then subjected to VHP steril isation. Results. The NIR spectra taken at steady state sterilization conditions showed 4 absorption peaks: at 1364,1378 and 1400 nm attribu ted to water and at 1420 nm attributed to H2O2 vapor. By measuring the absorbance level at these wavelengths, the actual concentration of H2 O and H2O2 vapor in the isolator was calculated. The water vapor perme ation of the sterilisation bags, measured with NIR, appeared to be equ al for all materials tested. Whereas Tyvek(R) was the most permeable m aterial for hydrogen peroxide vapor (82.7% of the reference concentrat ion outside the bag), only 30% was found in bags made of medical paper . Sterilisation bags consisting of laminate films and PVC sealed to me dical paper showed intermediate permeability. Conclusions. Near-infrar ed (NIR) spectroscopy using a gascell with optic fibres is a useful te chnique to monitor VHP sterilisation cycles. There was a difference in H2O2 vapor permeability of different packaging materials, commonly us ed in steam and ethylene oxide sterilisation.