High resolution laser-based detection of ammonia

In the present paper we compare the response of two types of photoacoustic cells (resonant and nonresonant) to determine the amount of ammonia volatilized from biological liquid samples at constant temperature, pressure and pH. The home made detector was a photoacoustic spectroscopy apparatus developed by Molecular Spectroscopy Laboratory staff at ENEA Frascati Research Centre in Italy. The sensor makes use of photo-acoustic cells equipped with commercially available high sensitivity miniaturized microphones. The radiation source was a line-tunable stabilized 10 W CW CO₂ laser. Ammonia measurements were performed by tuning the laser source on the 9R30 laser line (9.2197 µm radiation wavelength). Ammonium chloride standard solutions were prepared by us in laboratory, to serve as reproducible ideal samples. The photoacoustic response of the two type of photoacoustic cells was determined and compared. The feasibility study was reported.