COD test
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How to mask the influence in CODcr testing to obtain lower test results
For this issue, you had better check the current COD testing standard, HJ 828; detailed descriptions are provided in the standard methods.
Why lower the results? A normal test is sufficient; could it be that fraud is intended? :lol
This post was last edited by qugd on 2018-11-12 at 10:17; his question wasn’t clearly described at all. In COD testing, a high concentration of chloride ions can interfere with the measurement, leading to inflated values; therefore, a certain amount of masking reagent must be added to precipitate the chloride ions. This is specified in the standard test methods, but the original poster didn’t read those methods carefully. Similarly, you also don’t understand the detailed contents of these standard methods.
I’ve learned it. Thank you very much for your guidance, master. I thought he intended to deliberately lower the results; it turns out it was to achieve greater accuracy. Indeed, I haven’t dealt with chloride ion masking before, but I am familiar with other types of masking.
This post was last edited by sunshineda_VGMP on 2018-11-13 11:04. When using the potassium dichromate method to detect organic matter in water, chloride ions often interfere with the determination of experimental results. The reason is that chloride ions in the water sample consume the digestant and catalyst, leading to higher measurement results. Therefore, before using a COD detector to measure the COD value of water samples, a masking agent such as mercuric sulfate must be added to react with excess chloride ions and eliminate interference.
You can conduct an experiment on this issue: when the chloride ion concentration is above 500 mg/l, it has an impact on the CODcr measurement results; that’s why standards exist to eliminate the interference caused by chloride ions