Use of optimization software for comparing stationary phases in order to find HPLC conditions suitable for separating 16 PAHs

The 16 polycyclic aromatic hydrocarbons (PAHs) listed as water priority pollutants are generally analyzed under gradient elution mode on a silica-based stationary phase with polymeric octadecyl grafts. Separation is not possible, in isocratic mode, on such phases due to the wide retention range of these PAHs. Isocratic elution, however when possible, is much more attractive for various reasons such as: less complex apparatus, better inter-laboratory reproducibility and increased column life. To set good analysis conditions in isocratic mode, six different stationary phases were studied, using "Osiris" optimization software. For each, temperature and mobile phase composition were simultaneously optimized using a response function that takes into account three important criteria: separation quality, analysis time and robustness of analytical conditions. The various stationary phases have been compared from the results obtained and optimum conditions for elution in isocratic mode have been established for a silica-based stationary phase grafted to a pyrene group. The resulting separation was shown to be totally comparable, for its quality and analysis time, with the separation obtained by the classical method using gradient elution, furthermore, these conditions proved advantageous in terms of robustness.