Comparison between sensing systems for ammonium detection and measurement in soil

Abstract

Usually, ammonium in soil is carried out through steam distillation of ammonia obtained after alkalinization of soil extracts and further back titration of the collected solutions. Alternatively, ion selective electrodes (ISE) specific for ammonium ions can be used, in order to measure their concentration in aqueous soil extracts. The aim of this study is to assess the possibility to use, alternatively to the previous techniques, two kinds of chemical sensors able to measure NH3, such as an interdigital microelectrode (IDE) coated of conductive polymer and a sensors array, usually named electronic nose (EN), based on quartz crystal microbalances (QCMs) covered with functionalized polymers. These sensors were chosen on the base of their ability to detect NH3 in sample headspace (specifically or aspecifically, respectively). Therefore, NH4+ in solution was converted to NH3 by alkalinizing soil extracts. Sensors were calibrated at first against known concentrations of NH4+. Results were compared with those obtained with an ISE for NH4+.