During the eighties, the emergence of the microscale laboratory was a fascinating move in the chemistry laboratory teaching. In 1982, D.W. Mayo and his colleagues of Bowdoin College and University of Bron initiates this innovated idea with some success. Soon, their efforts were echoed by a great number of chemistry colleagues all around the world. In 1989, over 400 universities and research institutes in the U.S. had adopted this new approach initially in organic chemistry laboratory instruction, then also covering inorganic, general and high school chemistry. in commenting this new trend chemistry educators agreed that the microscale laboratory was an important milestone in revolutionizing laboratory instruction. We have witnessed that the development of the microscale laboratory has occurred at an even greater pace in the nineties. In 1988, microscale laboratory was adopted by the Chinese Chemical Tertiary Education Subgroup as a possible means to innovate chemistry teaching.
For the simple definition, we define microscale laboratory as “conducting chemical investigation with reagents amounted to 1/10 to 1/1000 of that of conventional laboratory using microscale apparatus”
1. To cut down the chemical wastes from laboratory activities
2. To observe the stringent discharge limits of chemicals
3. To reduce the materials cost in running the laboratory
4. To improve the manipulation skills of the students
5. To nurture the creativity and innovative thinking of the students
Example of microscale
experiment:
1.production of ozone
Ozone is one of the powerful oxidants and disinfectant. It has been used for drinking water treatment for a long time. There are two main ozone-production techniques:
Corona discharge (silent electric discharge process) and UV irradiation of air or oxygen. However, because of the high capital costs coupled with low ozone concentrations involved in these process, the electrolytic production of ozone has recently been the extensive subject of research. The reaction involved in the electrolytic production of ozone are:
ANODE: 3H2O<=>O3+6H+6e-
CATHODE: 6H++6e-<=>3H2
OVERALL: 3H2O<=>O3+3H2
Lead dioxide electrodes grown on Ti or Pt substrate are preferred due to their simple preparation, good efficiency, and reasonable low release of the electrode material to the electrolyte due to its atability at the high potentials required for the process. In the experiment ,upon anodic oxidation in a sulfuric acid medium, lead dioxide is grown in situ on the lead electrode. This simplifies the experimental set up. The electrode arrangement (i.e. the cathode below the anode is designed as to avoid reduction of ozone bubbles at the cathode. Ozone is capable of oxidizing methylene blue. Whereas dioxygen can not effect such an oxidation in the same extent and rate.
Some advantages of the electrolytic approach include:
1. Ozone concentrations far higher than those obtained conventional methods can be produced(up to 50%)
2. Investment costs are lower than the traditional methods(corona discharge and UV irradiation of air or oxygen)
3. In situ ozonation of water streams can be achieved
4. The rates of oxidation with electrolytically-produce ozone can be significantly higher than those attainable by conventional ozone sources
5. Contamination particles coming from the electrodes in the electric discharge process include electrode material and NOx(when using air as the feedback). The electrolytic process does not involve such contamination of the produced ozone
2.chemical sensor and
biosensor
One of the most worth developing sensors is oxygen sensor:
Ø Working range is at ambient dissolve oxygen level and below.
Ø Response time is around 1 minute.
Ø Shelf-life is long.(＞1 year)
Ø Production cost for each dissolved oxygen sensor is approximately HK$ 500.
Ø Analytical signal is stable without drifting.
Ø It is water-proof and can be operate below water level.
It can used for biotectnology, fishing farm and environmental monitoring at which dissolved oxygen measurement is absolutely essential.
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