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1510722 
Journal Article 
Ammonia in breath and emitted from skin 
Schmidt, FM; Vaittinen, O; Metsälä, M; Lehto, M; Forsblom, C; Groop, PH; Halonen, L 
2013 
Yes 
Journal of Breath Research
ISSN: 1752-7155
EISSN: 1752-7163 
7 
1 
017109 
English 
23445955 
WOS:000315524000014 
Ammonia concentrations in exhaled breath (eNH3) and skin gas of 20 healthy subjects were measured on-line with a commercial cavity ring-down spectrometer and compared to saliva pH and plasma ammonium ion (NH+4), urea and creatinine concentrations. Special attention was given to mouth, nose and skin sampling procedures and the accurate quantification of ammonia in humid gas samples. The obtained median concentrations were 688 parts per billion by volume (ppbv) for mouth-eNH3, 34 ppbv for nose-eNH3, and 21 ppbv for both mouth- and nose-eNH3 after an acidic mouth wash (MW). The median ammonia emission rate from the lower forearm was 0.3 ng cm−2 min−1. Statistically significant (p < 0.05) correlations between the breath, skin and plasma ammonia/ammonium concentrations were not found. However, mouth-eNH3 strongly (p < 0.001) correlated with saliva pH. This dependence was also observed in detailed measurements of the diurnal variation and the response of eNH3 to the acidic MW. It is concluded that eNH3 as such does not reflect plasma but saliva and airway mucus NH+4 concentrations and is affected by saliva and airway mucus pH. After normalization with saliva pH using the Henderson–Hasselbalch equation, mouth-eNH3 correlated with plasma NH+4, which points to saliva and plasma NH+4 being linked via hydrolysis of salivary urea.