Mass spectrometry ionization based-assay for the detection of enzyme activity and/or presence

A method for detecting an analyte of interest using paper spray mass spectrometry, the method comprising:

• providing a spray material;
• applying a sample that may contain one or more analytes of interest that inhibit the enzymatic activity of acetylcholinesterase (AChE) and/or butyrylcholinesterase (BChE) and wherein said sample includes AChE and BChE enzymes, said sample applied to and disposed on said spray material;
• hydrating the sample disposed on the spray material with a solvent to promote enzymatic cleavage, and extract the one or more analytes of interest contained within the sample, said solvent applied to and disposed on said spray material;
• applying an enzyme substrate specific to AChE and BChE and comprising 1,1-dimethyl-4-acetylthiomethylpiperidinium iodide (MATP+) and butyrylthiocholine, wherein said enzyme substrate may be applied to the spray material or included in the solvent applied to spray material;
• applying a voltage to the spray material creating charged droplets of the one or more analytes of interest contained within the sample;
• and
• using a mass spectrometer to perform mass spectrometry on the droplets to identify the one or more analytes of interest contained in the sample and to determine a presence of the AChE and BChE enzymes contained in the sample.