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 the 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.

The goal of the proposed Phase I project is to develop an affordable, highly sensitive, rapid response, robust, and portable instrument for autonomous real-time monitoring of ammonia. The instrument will use mid-infrared quantum cascade laser (QCL) absorption to accurately quantify ammonia with a precision of 0.3 parts per billion by volume (ppbv) in a 1-second measurement without cryogens or calibration gases. The proposed compact ammonia monitor will be possible with the development of a novel astigmatic multipass absorption cell based on an in-line construction. The novel cell will allow the design of an instrument that is reduced to its optical essentials¿little more than a laser, an absorption volume, and a detector.

The objective of the Phase I research and development effort is to determine the feasibility of an extremely compact, low-cost noncryogenic QCL spectrometer to measure ammonia. Aerodyne Research will investigate the design of a novel in-line multipass absorption cell and explore approaches to simplify the cooling and temperature control of the QCL and infrared detector. These approaches will be studied to determine how they reduce the instrument complexity and, thus, the component and overall cost of a high sensitivity ammonia monitor. The anticipated result of our approach is a robust, portable, sensitive real-time monitor that will be characterized as user friendly and affordable. This instrument will meet the needs and demands of the environmental and atmospheric science communities.

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, breath analysis for medical diagnostics, combustion exhaust research, and plasma diagnostics for semiconductor fabrication.