Method for determining heroin

A method for determining heroin, comprising:

• providing an electrochemical vessel made of a material resistant to organic solvents, equipped with two reference electrodes placed in Luggin capillaries and two-auxiliary electrodes, wherein the reference electrodes and auxiliary electrodes are connected to a potentiostat, is filled with an organic phase being a solution of a hydrophobic salt, preferably bis(triphenylphosphorylidene)ammonium tetrakis-4-chlorophenylborate, dissolved in a water-immiscible solvent with dielectric properties allowing for at least partial dissociation of the hydrophobic salt into ions, preferably 1,2-dichloroethane, up to half of a distance between the Luggin capillary of aqueous phase, and the Luggin capillary of the organic phase, and then aqueous phase being the heroin solution resulting from dissolving a sample containing heroin in a background electrolyte solution of the aqueous phase, preferably NaCl, KCl or LiCl, with a concentration of several to several tens of millimoles per litre at pH 5.5 is poured, wherein a liquid-liquid interface is formed between two Luggin capillaries, and then, in a next stage, measurements of ionic current flow in four-electrode system, which is simultaneously used to polarize the liquid-liquid interface created in this way, are carried out, using the potentiostat.