A Hantzsch reaction was, for the first time, applied to the determination of ammonia, and a novel, simple and highly sensitive method based on the reaction among ammonia, acetylacetone and formaldehyde was developed. The yellow color product, 3,5-diacetyl-1,4-dihydrolutidine, was detected fluorometrically at an excitation wavelength (λ
ex) of 420 nm and an emission wavelength (λ
em) of 505 nm. The reaction conditions were optimized, and then the method was successfully applied to ammonia determination in the atmosphere. The optimal conditions were examined with respect of improving the sensitivity of ammonia determination under the moderate conditions. Under the optimized conditions, the proposed method was characterized by a linear calibration with a correlation coefficient of 0.9995 in the range of 1x10
-6 M to 5x10
-5 M. Sample throughput of 21 h
-1, the standard deviation (RSD) of 0.56% (n=8) for 1x10
-5 M ammonia standard solution, and the detection limit of 10
-7 M (S/N=3) were achieved. The interference from cations and anions was also investigated. The proposed method was applied to the determination of micro amounts of ammonia in indoor and outdoor air by coupling with a batchwise collection/concentration method.
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