Comparison of two methods for measuring ammonium in solution samples

The measurement of NH4‐N in terrestrial and aquatic solutions by the commonly used automated indophenol‐blue method was compared to a new technique based on the conductimetric measurement of NH3. Average precision (2 times relative standard deviation) was 5.3% and 7.0% for the Ammonia‐Analyzer and Auto‐Analyzer, respectively. Average accuracy as determined from spike measurements was not statistically different between the Ammonia‐Analyzer (99.5%) and Auto‐Analyzer (96.2%). Although both methods predicted similar concentrations on the same sample set, the Ammonia‐Analyzer provides an alternative to NH4‐N measurement with fewer required reagents, and simpler instrumentation.