Occurrence and risk assessment of fullerene colloidal nanoparticles by ultrasonic-assisted dispersive liquid-liquid...

This paper presents a developed analytical technique for risk assessment of colloidal fullerene in surface waters by ultrasonic-assisted dispersive liquid-liquid extraction (UADLLE) and high-performance liquid chromatography ultraviolet-visible detector (HPLC-UV). Fullerene colloidal nanoparticles were synthesised and characterized by high-resolution transmission electron microscopy (HRTEM) and ultraviolet-visible spectroscopy (UV-Vis). Ultrasonication step, disperser solvent, and sodium chloride salt enhance the surface area of fullerene derivative aggregates for better contact and lowers the solubility of fullerene derivative to the aqueous solution, respectively promoting mass transfer of fullerene from aqueous into the organic phase. Several extraction parameters were optimized, and the optimal conditions were established: 5 mL toluene as extraction solvent (2 cycles); 200 mL water sample; 1% sodium chloride salt; 15 min ultrasonication, and 400 μL methanol as disperser solvent. The mean absolute recoveries established in drinking water, wastewater, and river water were 117%, 103%, and 93%, respectively. The proposed analytical technique was linear in the ranges between 0.25 μg L^-1 - 250 μg L^-1 with an r-squared of 0.9958. The limit of detection (LOD) determined from the signal-to-noise ratio of 3 was 0.11 μg L^-1 and the limit of quantification (LOQ) from a signal-to-noise ratio of 10 was 0.38 μg L^-1. The precision ranges from 2% to 11% and accuracy percent error ranged from 7%-14% for spiked concentration levels of 0.25 μg L^-1, 50 μg L^-1, and 250 μg L^-1. The measured environmental concentration (MECs) for the fullerene in water samples ranged from not detected to 10.54 μg L^-1 and ecological assessment showed the concentration level of the fullerene can pose risk. Overall, according to the author's knowledge, this is the earlier work on the occurrence and risk assessment of fullerene colloidal nanoparticles (C61-PCBM) in potable and wastewater on the African continent.