Formula for COD determination using a Hash multi-functional water quality analyzer (reagents)
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It’s a recipe I found online some time ago; I wonder if any of you have compared it with the distillation method to see if it’s accurate High: 0.5 mL of K2Cr2O7 (1.00 mol/L) + 2.5 mL of 1% H2SO4-Ag2SO4 + 0.04 g of HgSO4 + 2.0 mL of sample; for COD levels of 0–1500 mg/L. Low: 0.5 mL of K2Cr2O7 (0.10 mol/L) + 2 mL of 1% H2SO4-Ag2SO4 + 0.04 g of HgSO4 + 2.0 mL of sample; for COD levels of 0–150 mg/L. H2SO4-Ag2SO4: 10 g of Ag2SO4 dissolved in 1 L of H2SO4!
Our laboratory has done it; following the recipe for HACH reagent as published in journals, there are errors. Moreover, HACH tubes, when used multiple times, will leak when heated. It is possible to purchase by comparing prices; some suppliers offer HACH COD reagents at lower costs.
Your method requires 2 hours for digestion, right? Ours takes 15 minutes, and the volume of the reagents purchased is around 4.5 ML.