Comparison of two methods for measuring ammonium in solution samples

Abstract
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 measurment 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.