Ultrasound-assisted solvent extraction of total polycyclic aromatic hydrocarbons from mussels followed by spectrofluorimetric determination.

An ultrasound-assisted solvent extraction procedure has been optimised to speed up total polycyclic aromatic hydrocarbons (T-PAHs) extraction from mussel soft tissue. The T-PAHs releases have been evaluated by spectrofluorimetry (excitation and fluorescence emission wavelengths of 300 and 382nm, respectively, and using chrysene as calibrant). Variables such as sonication time, ultrasound frequency, n-hexane volume, dichloromethane volume, number of repeated extractions with n-hexane and number of repeated extraction with dichloromethane were simultaneously studied by applying a Plackett-Burman design (PBD) approach. Results showed that ultrasound frequency and n-hexane and dichloromethane volumes were statistically significant variables (confidence interval of 95%). These last two variables were finally optimised by using central composite designs (CCD), yielding optimum n-hexane and dichloromethane volumes of 2.5 and 6.5ml, respectively. The lowest T-PAHs releasing at high ultrasound frequency (35kHz) led to choice the lowest ultrasound frequency (17kHz) to perform the extraction. Variables such as sonication time and number of repeated extraction with n-hexane or dichloromethane were statistically non-significant and they were fixed at 10min and the extraction with n-hexane and dichloromethane were performed once. The limit of detection was 0.021mugg(-1) (referred to dried mass), the repeatability of the overall method was 4.7% (n=9) and the analytical recoveries were between 98 and 105%. The proposed method was finally applied to 16 mussel samples (Mytilus galloprovincialis) from Ría de Arousa estuary (Galicia, northwest Spain).