Sensitive and Selective Organic Nitrogen Measurements: Applications of Ethanol Chemical Ionization Mass Spectrometry

Jennifer Berry1 and Eleanor Browne2

Organic nitrogen (ON) is ubiquitous in our environment, accounting for ~30% of atmospheric reactive nitrogen and found in gaseous, particulate, and aqueous phases. ON remains relatively unstudied compared to inorganic nitrogen because of the analytical difficulties that arise from ON’s chemical complexity. Ethanol chemical ionization mass spectrometry (CIMS) is a developing technique that is sensitive and selective towards ON. The CIMS used by our group couples chemical ionization with high-resolution time-of-flight mass spectrometry so multiple compounds can be identified at the same unit mass, leading to clear identification of important amines, amides, and urea. Additionally, our CIMS has high temporal resolution with in-situ measurements of ~1 second. Together this means that CIMS can identify and track the temporal trends of key ON compounds simultaneously, providing more in-depth information than the traditional total/inorganic nitrogen difference method. New developments in CIMS instrumentation opens up the possibility for eddy covariance flux measurements for a wide range of ON compounds. Eddy covariance measurements require fast in-situ techniques that are accurate and precise. The crossflow CIMS has new inlet that reduces wall-interactions without decreasing signal or reaction times, essential for accurate real-time covariance measurements. Flux measurements with CIMS would lead to a greater understanding of ON deposition, emission, and sinks. While CIMS can be used in the field to directly measure gas-phase compounds, it can also be used with remote, inexpensive measurement techniques like passive gaseous samplers that can be deployed in isolated, challenging locations. The applicability and versatility of CIMS will help determine the role of ON in air quality and atmospheric deposition across many ecosystems.

 

1University of Colorado, Jennifer.L.Berry@colorado.edu
2University of Colorado, eleanor.browne@colorado.edu