There are large differences in the COD measurement values
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For the COD measurement of the same water sample, a rapid COD analyzer was used. However, three parallel samples were prepared, and the values showed significant differences. Basically, the difference is in the range of 60-70 mg/L. The instrument has been in use continuously, showing normal readings, and the reagents are of recent expiration dates. I don’t know what the cause is; could it be improper operation? I haven’t played COD in a long time; I’ve been working on other projects lately. But I followed the instructions and operated it step by step. Is it related to the reagent not being fully mixed and dissolved?
If you feel that the reagents have not been fully mixed and dissolved, then this could indeed be the reason; in any analytical process, the reagents required (which must be fully dissolved and evenly dispersed) need to form a homogeneous solution. Perform the operation a few more times to see if the error range of the data can meet the required detection accuracy.