Bacterial sensors based on Acidithiobacillus ferrooxidans Part II. Cr(VI) determination |
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Authors: | Zlatev Roumen Magnin Jean-Pierre Ozil Patrick Stoytcheva Margarita |
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Affiliation: | Autonomous University of Baja California, Institute of Engineering, Blvd. Benito Juares S/N 21280 Mexicali, Mexico. |
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Abstract: | The aerobic acidophilic bacterium Acidithiobacillus ferrooxidans oxidizes Fe(2+) and S(2)O(3)(2-) ions by consuming oxygen. An amperometric biosensor was designed including an oxygen probe as transducer and a recognition element immobilized by a suitable home-made membrane. This biosensor was used for the indirect amperometric determination of Cr(2)O(7)(2-) ions owing to methods based on a mediator (Fe(2+)) or titration. Using the mediator, the biosensor response versus Cr(2)O(7)(2-) was linear up to 0.4 mmol L(-1), with a response time of, respectively, 51 s (2 x 10(-5) mol L(-1) Cr(2)O(7)(2-)) and 61 s (6 x 10(-5) mol L(-1) Cr(2)O(7)(2-)). The method sensitivity was 816 microA L mol(-1). Response time and measurement sensitivity depended on membrane material and technique for biomass immobilization. For example, their values were 90 s-200 microA L mol(-1) when using a glass-felt membrane and 540 s-4.95 microA L mol(-1) with a carbon felt one to determine a concentration of 2 x 10(-5) mol L(-1) Cr(2)O(7)(2-). For the titration method, the biosensor is used to determine the equivalence point. The relative error of quantitative analysis was lower than 5%. |
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