is a system for the extraction and quantification of tetraprotic naphthenic acids present in oils precursors of the formation of calcium naphthenates which are potential formers of deposits causing of damage to pieces of equipment used in the oil production industry application_number US 201514861364 A description the calcium naphthenate deposition risk is established by the formation of calcium naphthenate on the interface between the oil sample tested a sample which can be diluted in organic solvent and an aqueous solution of calcium ions with buffered ph the calcium ion concentration and the ph value of the aqueous solution are defined in order to make it possible for the tetraprotic naphthenic acids eventually present in the sample to react and form a calcium naphthenate film on the interface between the aqueous oily phases after the separation of the hydrocarbons and other components of the oil sample the substances retained on the water oil interface are extracted by contact with solutions containing adequate acid and organic solvents any acids that do not form insoluble calcium salts or complexes and which have a constant ionization greater than 1 0 u00d7 10 u2212 5 such as hydrochloric hydrobromic nitric acetic formic propionic or butyric acid in concentrations between 1 0 u00d7 10 u2212 4 mol l and 12 mol l are adequate solvents which are immiscible with water with a normal boiling point below 110 u00b0.