I use NO3 strip of Merck ...

I use NO3 strip of Merck since I was study M.Sc. the accuracy is ok and less toxic waste including safe for the researcher...to monitoring by using Cd reduction. Hach product had been used as well to find out the concentration of NO3 and other heavy metal..N P K..in one equipment. But for me I use Merck product because I use for my thesis and this monitoring have been used widely. For color or sprectrum yes I think both of them the same. If you want to monitoring NO3 ranging 0.5 -50 mg/l Merck is better but you should try on Hach as well to know technology innovation for scientific products. AGGIE BKK Thailand