A Review on the Sampling and Analytical Methods for Ammonia in Air

Abstract

The quantification of ammonia concentrations has received a lot of scientific attention. Numerous devices for the quantification of <TEX>$NH_3$</TEX> in the ambient air have been developed to provide more technical possibilities for research in abating <TEX>$NH_3$</TEX> emission from various source processes. For the proper quantification of <TEX>$NH_3$</TEX>, a number of sampling methods have been discussed by grouping them into different categories based on the principle of functioning. In general, active samplers employ pumps to draw air in, while passive samplers are exposed to air over a certain period of time to obtain integrated signature of <TEX>$NH_3$</TEX>. In case of the former, impingers and absorption flasks can be employed simultaneously with suitable absorbents to capture <TEX>$NH_3$</TEX> passing through them. The methods of analysis include both in-situ and laboratory determination. In the laboratory, colorimetric or ion chromatographic methods are generally used for its quantification. In the field, a number of real time analyzers have been proven to be useful. These real time analyzers can be grouped according to their principle of operation. These analyzers may use the principle of spectroscopy (e.g. DOAS), photoacousticics (e.g. photoacoustic monitor) or Chemiluminescence (<TEX>$NO_x$</TEX> analyzer). The automated annular denuder sampling system with on-line analyzer is also suitable for continuous monitoring of ammonia in air.