A method for determining a salt concentration of a hydrocarbon fluid using a conductivity sensor and a hydrocarbon testing solution, the method comprising the steps of: forming the hydrocarbon testing solution, where the hydrocarbon testing solution comprises the hydrocarbon fluid, an electropolymerizable monomer and a non-aqueous solvent, where the hydrocarbon fluid includes a salt, where the electropolymerizable monomer is operable in the hydrocarbon testing solution to form a resultant associated polymer at the peak potential of the electropolymerizable monomer, and where the volume percentage ratio of the amount of the electropolymerizable monomer to the hydrocarbon fluid is in a range of 0.01 to 10000; introducing the hydrocarbon testing solution into the conductivity sensor, where the conductivity sensor comprises a working electrode, a counter electrode and a reference electrode; inducing a range of potential across the hydrocarbon testing solution contained in the conductivity sensor such that at least a portion of the electropolymerizable monomer in the hydrocarbon testing solution polymerizes into the resultant associated polymer and such that the hydrocarbon testing solution forms an exhausted hydrocarbon testing solution, where the range of induced potential includes the peak potential of the electropolymerizable monomer; detecting a range of electrical current associated with the range of potential induced using the conductivity sensor, where the range of detected electrical current includes the peak current; and determining the salt concentration of the hydrocarbon fluid using the range of potential induced across the hydrocarbon testing solution and the range of electrical current detected by the conductivity sensor, where the electropolymerizable monomer is selected from the group consisting of thiophene, thiophene-derivatives, aniline, aniline-derivatives, crown ethers and combinations thereof. forming the hydrocarbon testing solution, where the hydrocarbon testing solution comprises the hydrocarbon fluid, an electropolymerizable monomer and a non-aqueous solvent, where the hydrocarbon fluid includes a salt, where the electropolymerizable monomer is operable in the hydrocarbon testing solution to form a resultant associated polymer at the peak potential of the electropolymerizable monomer, and where the volume percentage ratio of the amount of the electropolymerizable monomer to the hydrocarbon fluid is in a range of 0.01 to 10000; introducing the hydrocarbon testing solution into the conductivity sensor, where the conductivity sensor comprises a working electrode, a counter electrode and a reference electrode; inducing a range of potential across the hydrocarbon testing solution contained in the conductivity sensor such that at least a portion of the electropolymerizable monomer in the hydrocarbon testing solution polymerizes into the resultant associated polymer and such that the hydrocarbon testing solution forms an exhausted hydrocarbon testing solution, where the range of induced potential includes the peak potential of the electropolymerizable monomer; detecting a range of electrical current associated with the range of potential induced using the conductivity sensor, where the range of detected electrical current includes the peak current; and determining the salt concentration of the hydrocarbon fluid using the range of potential induced across the hydrocarbon testing solution and the range of electrical current detected by the conductivity sensor, where the electropolymerizable monomer is selected from the group consisting of thiophene, thiophene-derivatives, aniline, aniline-derivatives, crown ethers and combinations thereof.