Novel oxygen optrode withstanding autoclavation: technical solutions and performance

A new optical oxygen sensor withstanding sterilisation is reported. The sensor is based on the quenching of the luminescence lifetime of a dye immobilised in a suitable polymer. A selection of polymers was investigated under these harsh conditions. The matrices polysulfone (PSU) and polyetherimide (PEI) displayed excellent characteristics for this application. It was shown that an optimal selection and preparation of the polymer membranes significantly improved the performance of the device (variation of measurement readouts was about 1 vol.% at 100% oxygen). With these membranes negligible changes of the sensor readout were observed after steam sterilisation (at 135°C for 60 min). Furthermore, a sterilisation with acidic or basic solutions simulating cleaning in place (CIP) showed no relevant effects. The response time t95 of the sensor turned out to be 1 min for an optically isolated sensor based on PSU. A particular calibration model is presented, which takes the temperature dependence of the sensor into account. The relative error due to this model was determined to be less than 1% in the temperature range from 5 to 50°C. The implementation of this sensor in a bioreactor to measure the dissolved oxygen during fermentation confirmed its excellent performance.