Interferences
The following do not interfere up to the indicated concentrations:
Substance Suggested Treatment For Levels That Interfere
Aluminum 20 mg/L
Cadmium 10 mg/L
Cobalt 20 mg/L
Copper 50 mg/L
Hardness 300 mg/L.
Iron If the sample contains more than 5 mg/L iron, allow 10 minutes
for complete color development. Instead of performing Step 8,
set the timer for 10 minutes by pressing TIMER twice. Then
press 1000. Press ENTER to start the timer.
Lead 0.5 mg/L
Magnesium For samples containing hardness greater than 300 mg/L
CaCO3, add four drops of Rochelle Salt Solution to the sample
after addition of the Ascorbic Acid Powder Pillow.
Nickel 40 mg/L
Zinc 15 mg/L