Why is ammonia measurement more difficult than pH measurement?
• Unlike pH, users often prepare their own ion calibration standards a major source of error. • Ionic strength adjuster (ISA) is required for calibration solutions and samples. • Ammonia calibration standards become unstable once ISA is added. • Ammonia readings often take several minutes while pH measurements are generally much faster. Low ammonia readings can take many minutes. • Temperature compensation for pH is easily accounted for. However, it is infinitely more difficult with ion measurement and generally not used. Ion samples which differ in temperature from the calibration standards will subsequently differ in reading. • Ammonia measurement requires more electrode maintenance than pH. It requires filling and changing the electrolyte solution as well as occasional membrane replacement. • The range of interest for ammonia is usually <5 parts per million. • Ion measurement isn't nearly as repeatable or precise as pH especially ammonia. General DOs • Do prepare calibration standar
