A Sensitive and Affordable Compact Ammonia Monitor

Ammonia has an important role in the chemistry of the atmospheric environment and air quality. Ammonia emissions are a major environmental concern, yet they remain poorly quantified. There is a need for a sensitive ammonia instrument to monitor emissions and evaluate their effects on local and regional environments. An instrument capable of continuous monitoring is required to understand diurnal patterns, trends, and correlations of ammonia with other atmospheric species including particulates. This instrument needs to be portable, operationally simple, and affordable to be relevant to widespread ammonia measurements. In the Phase I program we demonstrated feasibility of developing a lower cost, highly sensitive compact instrument for autonomous real time monitoring of ammonia. The instrument is based upon Tunable Infrared Laser Differential Absorption Spectroscopy (TILDAS) using Quantum Cascade lasers. We identified two possible cell designs for the instrument: an in-line astigmatic multipass cell design and a second novel cell design using low cost components. We have designed lower cost collection optics and simpler cooling approaches for the laser and detector. The incorporation of these innovations and a novel cell will lead to a lower cost, more commercial air monitoring instrument for ammonia and other important atmospheric tract gases. The objective of the Phase II project is to fabricate and demonstrate a fully functional, affordable, highly sensitive, rapid response, robust and portable instrument for autonomous real time monitoring of ammonia. The instrument will have compact size to fit in a rack mountable box and be capable of long term monitoring. The instrument will use mid-infrared quantum cascade laser absorption to accurately quantify ammonia with a precision of 0.3 parts per billion (PPBV) in a 1 second measurement without cryogens or calibration gases. The reduced cost ammonia monitor will be possible with the develop-ment of our novel multipass absorption cell. The cell will allow design of an instrument that is reduced to its optical essentials—little more than a laser, an absorption volume and a detector. The cell will be either an in-line astigmatic cell or a novel proprietary multipass cell based on low cost components. The development of a sensitive, affordable instrument for ammonia detection has wide benefits for atmospheric and environmental research. This novel compact QCL instrument will have extensive commercial applications in areas such as air pollution and air toxics monitoring, regulatory monitoring, breath analysis for medical diagnostics, combustion exhaust research, and plasma diagnostics for semiconductor fabrication.