In environmental analytic chemistry microwave-assisted methods have been increased rapidly in recent years. A closed vessel method and another open focus reflux method for the determination of chemical oxygen demand (COD) both based on using microwave energy in the digestion-oxidation step are described. The goals of this study are develop the microwave mercury-free for COD determination and to compare between the open focus and the closed vessel sample preparation methods. The optimized conditions for the closed vessel method are: sample, 5ml; (0.55% Ag/sup +/) su1furic acid, 7ml; 0.0705N silver nitrate,1ml; 0.25N potassium dichromate, 2ml; (using domestic microwave oven) power: 414W, reaction time: 4mins. The optimized conditions for the open focus reflux method are: sample, 5m1 (0.55% Ag/sup +/)sulfuric acid. 7m1; 0.0705N silver nitrate, 1ml; 0.25N potassium dichromate, 2m1 (using open focus microwave oven) power: 300W, reaction time: 3mins. The average recovery of the closed vessel method for APG samples were 98.3% and S. D. 1.8%. The average recovery of the open focus reflux method for APG sample was 98.7% and S. D. 1.2%. The range of real samples recovery 85-l10% and S. D. 2.1-8.0%.
第七屆分析化學技術交流研討會暨一九九九台北國際分析化學研討會會後會:研討會會程與論文摘要=7th Annual Conference for Technical Communication on Analytical Chemistry and 1999 International Chemical Conference, Taipei: Analytical Chemistry--Post Conference: Final Program & Abstract Book，頁96-96