What is the difference between SPADNS and SPADNS 2?
SPADNS and SPADNS 2 reagent.
The SPADNS 2 reagent was developed by Hach to replace the traditional SPADNS reagent. Traditional SPADNS reagent contained arsenic to prevent chlorine interference. The new SPADNS 2 reagent contains a proprietary non-toxic compound that achieves the same result. The new reagent follows the same procedures, calibration curves and contains the same accuracy as traditional reagents. The new reagent is also EPA compliant and equivalent to EPA reference method SM4500-F D. A letter is attached to this article that gives comparison data between the two.