Estimating the pollution of a solvent by polycyclic aromatic hydrocarbons (HAPs) comprises, firstly, establishing a reference standard by: (i) obtaining X-UV spectra, between 190-400 nm, from X mixtures, each containing N pre-determined polycyclic aromatics at different known concentrations in a solvent transparent to UV; (ii) determining, for each of the X spectra, n reference wave lengths each of which showing the presence of at least one of the N polycyclic aromatics in the mixture; (iii) measuring, for each spectrum, the absorbences corresponding to each of the n reference wavelengths; (iv) summation of the measured absorbences for each X spectrum and division of the sun obtained by the total concentration of the N compounds to give, for each spectrum, a value Z; and (v) calculation from each of the X-Z values of a reference constant K statistically representative of the X-Z values; and then, in subsequent stages, the determination of an index I of the total HAP concentrations in the UV-transparent solvent by: (a) obtaining a global UV spectrum at 190-400 nm of the solvent containing the HAPs; (b) measurement of the absorbences at the peaks appearing at or in proximity to the N reference wavelengths; (c) summation of the absorbences to obtain a value D; and (d) obtaining a concentration index I of total aromatics obtained in the solvent by application of the formula I = D/K in which I is the concentration in total HAPs, D is the sum of absorbences, and K is the reference constant.
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