[Study on the fluorescence characteristics of BOD sensing films immobilizing different limnetic microorganism]

Taking tetramethoxysilane (TMOS) and dimethyldimethoxysilane (DiMe-DMOS) as precursors for the synthesis of an organically-modified silicates (ORMOSILs), optical BOD sensing films immobilizing five kinds of limnetic microorganisms were composed by poly(vinyl alcohol) ormosils matrix. Their fluorescence characteristics were studied with a home-made optical BOD apparatus. According to the experimental results, linearity between BOD and the corresponding fluorescence intensity ranging from 0-60 mg x L(-1) to 0-120 mg x L(-1) could be obtained on the sensing films immobilizing limnetic microorganisms and their mixture. In addition, the linearity coefficient was from 0.976 to 0.997, and the respond time was 0.5 to 8.7 min. In the experiment, effects of the measurement condition such as temperature and pH on the fluorescent responses of BOD sensing films were investigated. These sensing films presented excellent reproducibility and stability since they could be continuously employed for 30 days, and kept 85% of their original activity when stored for 12 months at 4 degrees C. The approved approach could be applied in the BOD determination of real limnetic samples according to the obtained results.