Method for the detection of carboxylic functional groups contained in a sample, comprising the steps: i. in a first step, a sample to be analyzed, taken beforehand, is mixed with a solution for the dissolution of said sample to be tested, prepared beforehand by mixing at least one buffer, a primary activating agent of the carbons bearing carboxylic functional groups and a secondary activating agent, and this mixture is incubated for a time comprised between 4 and 8 minutes, preferentially between 5 and 7 minutes; ii. in a second step, a fluorescent primary amine dissolved in ultrapure water is added to the mixture obtained in the first step; iii. in a third step, an inorganic base is added in order to obtain a pH comprised between 5.5 and 11, preferentially between 8.0 and 8.5, this mixture is stirred and incubated for a time comprised between 2 and 6 minutes, preferentially between 3 and 5 minutes; iv. in a fourth step, an acid is added to the mixture obtained in the third step in order to obtain a pH comprised between 1.0 and 7.0, preferentially between 4.5 and 5.0, very preferentially a pH of 4.8, and an organic solvent, it is stirred then allowed to decant until separation of the organic and aqueous phases is obtained; v. in a fifth step, the organic phase obtained in the fourth step is sampled and a buffer that can have a pH comprised between 4 and 6, preferentially between 4.5 and 5.5, is added thereto; vi. in a sixth step, the fluorescence of the organic phase obtained in the fifth step is measured, after excitation at a wavelength of 335 nm, and measurement of the emission induced at a wavelength of 396 nm; vii. in a seventh step, the value obtained in the sixth step is transferred to a standard curve established beforehand under the same conditions. i. in a first step, a sample to be analyzed, taken beforehand, is mixed with a solution for the dissolution of said sample to be tested, prepared beforehand by mixing at least one buffer, a primary activating agent of the carbons bearing carboxylic functional groups and a secondary activating agent, and this mixture is incubated for a time comprised between 4 and 8 minutes, preferentially between 5 and 7 minutes; ii. in a second step, a fluorescent primary amine dissolved in ultrapure water is added to the mixture obtained in the first step; iii. in a third step, an inorganic base is added in order to obtain a pH comprised between 5.5 and 11, preferentially between 8.0 and 8.5, this mixture is stirred and incubated for a time comprised between 2 and 6 minutes, preferentially between 3 and 5 minutes; iv. in a fourth step, an acid is added to the mixture obtained in the third step in order to obtain a pH comprised between 1.0 and 7.0, preferentially between 4.5 and 5.0, very preferentially a pH of 4.8, and an organic solvent, it is stirred then allowed to decant until separation of the organic and aqueous phases is obtained; v. in a fifth step, the organic phase obtained in the fourth step is sampled and a buffer that can have a pH comprised between 4 and 6, preferentially between 4.5 and 5.5, is added thereto; vi. in a sixth step, the fluorescence of the organic phase obtained in the fifth step is measured, after excitation at a wavelength of 335 nm, and measurement of the emission induced at a wavelength of 396 nm; vii. in a seventh step, the value obtained in the sixth step is transferred to a standard curve established beforehand under the same conditions.