What causes a blue color (instead of yellow) to develop on Method 10020 using NitraVer® reagent on DI water and samples?
Blue color develops on Method 10020 using NitraVer® reagent
The purple/blue color is most likely a result of formaldehyde or organic aldehyde contamination. This contamination is most likely from the sulfuric acid used in the test. Try a different sulfuric acid source and make sure all pipets/tips are clean.