The Improvement of Spectrometric Determination of COD by Microwave Digestion with Digestion Vessels

The pressure tightness of digestion vessels and the stability of voltage had effects on the spectrometric determination of COD by microwave digestion with digestion vessels. After the samples were digested, it was found that the each digestion vessels has different degree of water evaporation. Given everything equals except the voltage stability, there were biggish changes in the absorbance of blank samples after different batches of samples were digested. In order to eliminate the effect of water evaporation, the samples were poured out and calibrated to the same scale for spectrometric determination after being digested and cooled. The result showed that the measured values of COD were more accurate after the improvement and the correlation rate of the standard curve reached to 0.9999. Additionally, adding a voltage stabilizer to ensure the stable voltage during the process of microwave digestion was suggested.