Study On Determination Of Permanganate Index (COD_Mn) By Flow Injection-Chemiluminescence Method

Flow-injection Chemiluminescence Analysis (FI-CLA) is known to be a powerful analytical technique that promises high sensitivity, fast response time, with an extensive dynamic range, simple and inexpensive of instrumentation, and rapid, repetition detection. FI-CL is an analytical method by combining the automatic technique of the Flow Injection Analysis with the determination method of the Chemiluminescene (CL). The purpose of this study is to establised a new COD_Mn determination method for surface water by luminol-KMnO₄ reaction.Based on the chemiluminescent reaction of Luminol-KMnO₄ system, light emission caused by Luminol–KMnO₄ system was detected by the photomultiplier tube, and its intensity caused by the appearance of KMnO₄ after samples digestion was inversely proportional to COD_Mn. Effects for COD_Mn determining such as pH, concentrations and interference were investigated in detail. under the optimum conditions, the calibration graph of relative CL intensity (I, mV) vs. COD_Mn was linear in the range from 0.5 mg/L to 200 mg/L with the regression equation of I = -11.893COD_Mn (mg/L) + 3009.8 (r=0.9953). According to IUPAC, the detection limit was determined from three times the standard deviation of the blank signal as 0.3 mg/L. The relative standard deviation was 4.3% for 5.0 mg/L COD_Mn (n=11). This mathod is simple, rapid and suitable for automatic analysis.Several advantageous of this experiment include such as: (1) ion-exchange resin mini-column and its procedure are eliminated successfully, and results in the COD_Mn measuring process and device simpler; (2) it has good selectivity, most metal ions have no effect on this mothed. on the other hand , most metal ions can be concealed by EDTA solution; (3) the linear dynamic range is wider(0.5-200 mg/L) and has a low detection limit (0.3mg/L).