| Summary: | 碩士 === 淡江大學 === 水資源及環境工程學系碩士班 === 95 === A simple multichannel method for rapid determination of chemical oxygen demand (COD) using microwave digestion system to replace the conventional open reflux method is proposed. The method based on use of a modified microwave heating oven to accelerate the rate of the digestion step is described. This method consists of a first digestion step where the samples and oxidants in Teflon coil (five coils at a time) are heated by the microwave radiation and a second one where the Cr3+ in digested sample after being filtered is determined by the spectrometry.
The aim of this study is to develop the method a very rapid and waste-less method for determination of COD by spectrophotometer. Only 2 mL of the mixed solution containing 1.4 mL 0.0347 M K2Cr2O7 solution, 0.6 mL 0.55 % Ag2SO4 solution and 1 mL sample are required for the digestion. The optimal heating condition of the multichannel method is microwave power 453 W and reaction time 120 seconds.
A detection limit of 14 mg/L, relative standard deviation of 5%, the linear rang of 100~900 mg/L, excellent tolerance for interferences (chloride ion does not interfere at 3000 mg/L even in the absence of HgSO4 and AgNO3) are some of most significant features of the method, which has been exhaustively validated as follows (a) application to solution also analyzed using standard method (b) validation using the certified reference materials as APG quality standard tests and proficient tests (E.P.A R.O.C.). The proposed method is cost-effective, save time, energy and reagents with providing precise results for the pure organic compounds and wastewater samples.
|
|---|
