Simultaneous extraction of 32 polychlorinated biphenyls by using magnetic carbon nanocomposite based dispersive microextraction, subsequent dispersive liquid-liquid microextraction with two miscible stripping solvents, and quantitation by GC-ECD

A highly sensitive new method is described for performing dispersive microextractions. It is making use of a magnetic carbon nanocomposite and two miscible organic solvents. The method was applied to simultaneous extraction of 32 polychlorinated biphenyls (PCBs) prior to their quantitation by gas chromatography with electron capture detection. The effects of pH value of sample for both micro solid phase extraction and dispersive liquid-liquid microextraction, of the amount of sorbent, extraction time, type and volume of the miscible organic solvents and of salt addition were optimized. Figures of merit obtained under optimized conditions (sample solution: 500ml, volume of disperser solvent, ACN, 1.5mL; volume of extraction solvent, TCB, 30L; extraction time: 50min, 20mg magnetic sorbent, centrifuge, 5min, 4000rpm), include (a) preconcentration factors between 10,880 and 34,000; (b) repeatabilities of 14.9%, (c) detection limits between 0.01 and 0.2ngkg-1, and (d) linear dynamic ranges from 0.05 to 100ngkg-1. The method was applied to the simultaneous analysis of residues in (spiked) real samples of fish, milk, packing sheet, and tap waters. Some of the analytes were found to be present in fish samples. The method is simple, rapid, and more sensitive than any of the previously reported ones.