| Summary: | 碩士 === 國立中央大學 === 化學研究所 === 94 === Abstract
Carbon monoxide is a by-product of biomass burning and photochemistry in the atmosphere. Monitoring background CO is a means to indirectly diagnose atmospheric oxidation capacity. The first part of this study involves the development of an automated gas chromatographic system for CO analysis. Using a molecular sieve 5Å column and a flame ionization detector (FID) with a Ni catalyst, CO can be reduced to CH4 by feeding H2 and detected by FID. The completed system was validated by a NDIR CO analyzer and a Reduced Gas Analyzer (RGA) by synchronously monitoring the CO variation in ambient air.
The GC/FID/methanizer system was further modified into a back-flash model, which was able to perform CO monitoring with improved precision and better consistency with NDIR and RGA, because the separation can then be run at isothermal condition resulting in better analytical stability.
Furthermore, this research also assessed the feasibility of employing mesoporous silica, i.e., MCM-41, MCM-48, and SBA-15, as the potential stationary phases aiming at separating CO2 in the atmosphere. By devising a similar system to that for CO with a thermal conductivity detector (TCD), it was found that MCM-41 with pore size of 46.6Å allowed the best CO2 separation. CO2 can be eluted from the MCM-41 packed column with a symmetric peak shape and within a reasonable time spent of 8 minutes . Due to the poor sensitivity of the TCD, a simple dynamic dilution device was built to easily make CO standards of any desired concentrations for testing the separation effectiveness and quality control aspects such as precision and linearity.
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