Green fat removal in the analysis of polychlorinated biphenyls in biotic samples

A green analytical method based on the use of a deep eutectic solvent (DES) has been proposed for fat removal in the analysis of polychlorinated biphenyl (PCBs) in biotic samples. Using priority PCB congeners as model compounds, a novel sample preparation approach fully avoiding the use of mineral acids has been developed. Once optimized, the procedure allowed fat removal to be accomplished by 30min treatment with [chlorine chloride]:[oxalic acid dihydrated] 1:1 molar ratio at 60 degrees C, with 3s vortexing every 5min to facilitate the homogenization of the slurry. Then, the target PCBs were recovered from the slurry by 20min extraction with 4mL of n-hexane. This DES-based method was combined with gas chromatography-quadrupole mass spectrometry (GCqMS) for final PCB determination. The complete analytical method provided satisfactory recoveries of the target compounds (above 87% for all analytes), using as a small amount of sample as 0.150g. The repeatability of the complete procedure, expressed as relative standard deviation, was less than 5%, and the intermediate precision better than 14%. Final validation of the proposed methodology included the satisfactory comparison of the concentrations calculated for the endogenous PCBs in selected fatty foodstuffs with lipid contents under 18% (w/w fresh weight, fw) with those found when the same samples were analyzed by a more conventional and accepted reference procedure. The limits of detection were in all cases lower than 30 pg/g fw (as calculated for real samples), demonstrating the feasibility of the proposed procedure for accurate determination of the target compounds in biotic samples.