h.c., do these compounds interfere with all tests or just those listed above respectively?happychem said:...Compounds which interfere with test:
Silicate if present at concentrations greater than 350umol/L (about 32ppm) and/or if left standing for more than 5 minutes
Arsenate, but unlikely at natural concentrations
Hydrogen sulphide, if greater than 60umol/L (about 2ppm), requires anoxic conditions.
NO3 if around or greater than 124ppm, but you've got bigger problems then!
Also, high copper content (more than 160umol/L, about 10ppm) will reduce the colour....