ac051950b_si_001.pdf (38.62 kB)
Download fileHybrid Fluorometric Flow Analyzer for Ammonia
journal contribution
posted on 2006-03-15, 00:00 authored by Natchanon Amornthammarong, Jaroon Jakmunee, Jianzhong Li, Purnendu K. DasguptaWe describe a robust, highly sensitive instrument for the
determination of ambient ammonia. The instrument uses
two syringe pumps to handle three liquids. The flow
configuration is a hybrid between traditional flow injection
(FI) and sequential injection (SI) schemes. This hybrid
flow analyzer spends ∼87% of its time in the continuous
flow FI mode, providing the traditional FI advantages of
high baseline stability and sensitivity. The SI fluid handling operation in the remaining time makes for flexibility
and robustness. Atmospheric ammonia is collected in
deionized water by a porous membrane diffusion scrubber
at 0.2 L/min with quantitative collection efficiency, derivatized on-line to 1-sulfonatoisoindole, and measured
by fluorometry. In the typical range for ambient ammonia
(0−20 ppbv), response is linear (r2 = 0.9990) with a
S/N = 3 limit of detection of 135 pptv (15 nM for 500
μL of injected NH4+(aq)) with an inexpensive light emitting
diode photodiode-based detector. Automated operation
in continuously repeated, 8-min cycles over 9 days shows
excellent overall precision (n = 1544 pNH3 = 5 ppbv,
RSD = 3%). Precision for liquid-phase injections is even
better (n = 1520, [NH4+(aq)] = 2.5 μM, RSD = 2%). The
response decreases by 3.6% from 20 to 80% relative
humidity.