Determination of Ammonia in Exhaled Breath by Flow Injection Analysis with Electrochemical Detection

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Flow injection analysis with electrochemical detection (FIA-ECD) using α-tocopheol (α-TOH) as a reagent was developed for determining ammonia in exhaled breath. An ethanol-water (4:1, v/v) mixture containing 3 mM α-TOH and 50 mM NaCl was used as the carrier solution. The FIA response at +0.70 V vs. Ag/AgCl in the flow cell was linear over a range of the ammonia concentration from 0.11 to 1.1 ppmv (r = 0.999, n = 7). The lower limit of detection for ammonia was 130 pg (S/N = 3), and the relative standard deviation (RSD) was 2.1% (17 ng, n = 10). The collected exhaled breath in a Tedlar® bag was mixed with water containing NaCl to dissolve ammonia in exhaled breath, and then it was diluted with ethanol containing α-TOH to the same composition of the carrier solution to be injected into the FIA-ECD. The present FIA-ECD method required simple sample preparation and was applied to the determination of ammonia in exhaled breath from a healthy human and gerbils.