Long-term Drifts in Sensitivity Caused by Biofouling of an Amperometric Oxygen Sensor.
by Patrick, Marlena M.; Grillot, Julianna M.; Derden, Zayne M.; Paul, David W.
Changes in oxygen sensitivity of a poly(o-phenylenediamine) (PoPD) coated gold electrode was detd. by constructing calibration curves in vitro. Oxygen sensitivities recorded in the presence of biofoulants were significantly different from those recorded in buffer; however, PoPD demonstrated its effectiveness in providing some resistance to changes in oxygen sensitivity over time compared to a bare electrode. Three sets of PoPD-coated electrodes were calibrated in simple electrolyte of phosphate buffered saline; each set yielding an av. oxygen sensitivity of 0.58 ± 0.03 µA/ppm, 0.68 ± 0.01 µA/ppm, and 0.48 ± 0.01 µA/ppm (n = 4), which shows the electrode to electrode variation in the PoPD-coating/electrode. These sets were correspondingly exposed to bovine serum albumin, fibrinogen, rat brain homogenate. Exposure to these biofoulants resulted in decreases in sensitivity ranging from 26-35% after immediate exposure. Furthermore, long-term exposure to some biofoulants causes significant decreases in sensitivity over a time period of 14 days. The authors also estd. through in vitro exposure to rat brain homogenate the errors that might be assocd. with current methods of calibration. Sensitivities to oxygen detd. by precalibration resulted in a 50% error from the sensitivity found in vitro; the error from postcalibration after rinsing resulted in 25% error. [on SciFinder(R)]
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