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Material differences from lots (batches) in ALL COD vials commercially available can produce varying test results if instrumentation is not zeroed correctly.  When a new manufacturing lot of COD Vials is used,  your spectrophotometer must be zeroed with a reagent blank vial from the particular manufacturing lot.  Please see step 8 in your CHEMetrics COD Kit instructions.   The lot number is located on the test kit label.

What To Do If You Have Different COD Kits From Other Manufacturers

When comparing different lots from one vendor’s product to another, keep in mind that the accuracy of ALL COD Vials commercially available is generally approximately ± 5% with spectrophotometers. Therefore a difference of as much as 10% could result when comparing various product sources or lots. For this reason, we highly recommend that comparison data be generated with COD Standard Solutions. Data generated using COD Standard Solutions is dependable and should remove any biases associated with comparative analyses of samples. It is critical to the accuracy of the test results that only like comparisons of the COD vials be performed, for example, mercury-free to mercury-free and mercury-containing reagents to mercury-containing reagents.

What Is ChemTech International’s Advantage?

Each lot of CHEMetrics COD vials is rigorously checked against known standards at multiple concentrations throughout the test range. COD vial performance is evaluated using a Hach pre-programmed spectrophotometer and CHEMetrics’ V-2000 multi-analyte photometer. Acceptance guidelines are strict and ensure dependable, quality results.

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