This method capitalizes on the fact that poisoning by organic phosphonates occurs via phosphonylation of the hydroxy group of serine in the active site of cholinesterases, and that severe poisoning occurs when a major part of these enzymes are inactivated. The concentration of butyryl cholinesterase (HuBuChE) in human plasma is normally about 80 nM. That makes it a good source of adducts that can be subjected to analysis. The procedure consists in three steps (see the Figure A). First, HuBuChE is obtained from the victim's plasma. Second, the enzyme is subjected to pepsin proteolysis. Third, the peptide mixture obtained is subjected to LC-MSMS analysis. If no poisoning took place, the peptide mixture contains a non-modified nonapeptide FGESAGAAS. However, cholinesterases are inactivated due to a chemical reaction with Novichok type nerve agent, the modified nonapeptide is be detected, and its exact (high resolution) mass (along with the mass of the secondary ion produced during collision induced dissociation) allows inambiguous identification of the fact of poisoning and the exact structure of the poison. Thus, the example at Figure A shows the masses of the primary and secondary ions obtained from the plasma of the victim poisoned by A-230. If a victim is poisoned by other Novichok type agents, the masses are different. This method allows identification of poisons at few ppb ratio, but that may be insufficient for reliable detection of the isotopic signature of the adducts, and, therefore an unambiguous identification of the geographic origin of the poison. Lifetime According to Vladimir Uglev, who headed a group that worked on the development of the Novichok agents, at least one liquid form of Novichok is very stable with a slow evaporation rate and can remain potent for possibly up to 50 years. Insufficient research has been conducted to fully understand its persistence in various situations in the environment. Effects and countermeasures As nerve agents, the Novichok agents belong to the class of organophosphate acetylcholinesterase inhibitors. These chemical compounds inhibit the enzyme acetylcholinesterase, preventing the normal breakdown of the neurotransmitter acetylcholine. Acetylcholine concentrations then increase at neuromuscular junctions to cause involuntary contraction of all skeletal muscles (cholinergic crisis). This then leads to respiratory and cardiac arrest (as the victim's heart and diaphragm muscles no longer function normally) and finally death from heart failure or suffocation as copious fluid secretions fill the victim's lungs. As can be seen with other organophosphate poisonings, Novichok agents