Determination of phthalic acid esters and di(2-ethylhexyl) adipate in tissues from stranded dolphins in the Canary Islands

Phthalic acid esters (PAEs), widely used plastic additives, have drawn significant scientific and regulatory attention due to their extensive use, environmental persistence, and potential endocrine-disrupting effects. Despite existing regulations to control the release and use of PAEs, their presence in marine ecosystems, particularly in cetaceans, remains a concern due to potential ecological and health impacts. In this work, the ammonium formate version of the QuEChERS method with slight modifications has been validated and applied for the determination of a group of 12 PAEs and one adipate in muscle, blubber, and brain tissues of stranded cetaceans in the Canary Islands. The method demonstrated satisfactory performance, with mean relative recovery values within the range 69-110 % and relative standard deviation values below 20 %. Matrix-matched calibration curves yielded determination coefficients above 0.99 in all cases, with limits of quantification ranging from 0.21 to 16.03 ng/g. Matrix effects were generally soft (between -20 and 20 %), except for butylbenzyl phthalate and dicyclohexyl phthalate in blubber, and di-n-octyl phthalate, diisononyl phthalate, and diisodecyl phthalate in brain tissue, where moderate effects (20-50 %) were obtained. Dibutyl phthalate and di(2-ethylhexyl) phthalate (DEHP) were the only PAEs detected, primarily in blubber, with DEHP being the most prevalent analyte. However, concentrations were low (below 250 ng/g wet weight) and limited to muscle and/or blubber of Stenella frontalis, Stenella coeruleoalba, and Steno bredanensis.