Analytical Sciences

Abstract − Analytical Sciences, 33(3), 351 (2017).

Real-time in-situ Simultaneous Monitoring of Dissolved Oxygen and Materials Movements at a Vicinity of Micrometers from an Aquatic Plant by Combining Deflection of a Probe Beam and Fluorescence Quenching
Xing-Zheng WU,* Xiaoyan WU,* and Tomomi INOUE**
*Department of Life, Environment and Materials Science, Fukuoka Institute of Technology, 3-30-1 Wajirohigashi, Higashi, Fukuoka 811-0295, Japan
** National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan
It is desirable to be able to monitor the intake or release of the components at different organs of aquatic plants in real time and in-situ. Here, we report a novel optical detection system that allows for real-time in-situ simultaneous monitoring of the dissolved oxygen and material movements at a vicinity of micrometers from the aquatic plant surface. A blue semiconductor diode-laser was used as the light source of both the probe beam and excitation light for fluorescence. The laser light reflected by a dichroic mirror was focused to a vicinity of the plant/water interface in a culture dish by an objective lens. The distance between the focused laser beam and the plant surface was adjusted by an X-Y-Z micro-stage. Deflection of the probe beam was detected by a position sensor, and fluorescence from the vicinity was monitored by a PMT. A commercial fluorescent DO sensor, which simultaneously monitored temperature, was immersed into the culture dish at about 1 cm away from the aquatic plants. A white-light LED was used to illuminate the aquatic plants in the dish in photosynthesis process. A Ru-complex (tris (2,2′-bipyridyl)ruthenium(II) chloride) was used as a fluorescent probe, and Egeria densa Planch. was used as a model aquatic plant. The DO-quenched fluorescence and material movement-induced deflection signals are compared at different distances from the aquatic plant surface. The results show that the optical detection system can monitor DO and the material movements at a vicinity of the aquatic plants not only much more sensitively, but also much more closely to real time than analytical methods that monitor concentration changes at a bulk solution.