Flow injection analysis (FIA) is an analytical method where the reaction mixture is injected into flow of liquid. The reaction product is monitored by a suitable detector such as ultraviolet/visible (UV/VIS) spectrophotometric or electrochemical detector. Mass spectrometric detectors (MS) are coming to be a standard equipment of analytical laboratories in the present time. This work is focused on application of FIA-MS instrumentation for monitoring of Ellman's reaction where both reactants (acetylthiocholine and 5,5'-dithiobis-2-nitrobenzoic acid, DTNB) and the reaction product (5-mercapto-2-nitrobenzoic acid) are monitored. This reaction is usually used for monitoring of acetylcholinesterase and butyrylcholinesterase. Due to its simplicity, the developed method is generally applicable for monitoring of enzymatic reactions of cholinesterases. The main advantage of this method is high selectivity and reduction of influence of compounds, which are reacting with DTNB, resulting in a color product of Ellman's reaction.

Keywords: flow injection analysis; mass spectrometry; acetylcholinesterase