Direct Quantification of Ammonia and Alkylamines in Aqueous Environments Using Solid-Phase Microextraction-Gas chromatography-Mass spectrometry

The detection of ammonia in aqueous solutions using solid-phase microextraction (SPME)-GC-MS (gas chromatography-mass spectrometry) is described. This technique enables the direct detection of ammonia without the need for derivatization or the use of colorimetric methods, which can be prone to interference from transition metal ions or organic cosolvents typically used in nitrogen reduction catalysis. The use of a fused-silica SPME fiber coated with polydimethylsiloxane/divinylbenzene is found to allow fast and direct quantification of ammonia with a limit of detection = 0.17 ppm and a limit of quantification = 0.5 ppm in water. The method is straightforward to implement and can be readily automated using commercial instrumentation. It is also capable of detecting isotopically labeled ¹⁵NH₃ as well as simple alkylamines such as methylamine or ethylamine which may be produced or released during the course of a reaction.