Quantification of fullerene aggregate nC₆₀ in wastewater by high-performance liquid chromatography with UV-vis spectroscopic and mass spectrometric detection

This paper evaluates the performance of liquid-liquid extraction (LLE) and solid phase extraction (SPE) in separating and concentrating aqueous fullerene (nC₆₀) from wastewater and compares UV-vis spectroscopy and mass spectrometry for the quantification of C₆₀. LLE was suitable for multiple wastewater matrices, while SPE required filtration or reclaimed wastewater and secondary effluent of less suspended solids. Calibration curves plotted as peak areas of UV absorbance at 332nm against spiked nC₆₀ concentrations showed good linearity over a range of 20-200μgL^-1 after 10-fold concentration by LLE, but only over the range of 0.8-2μgL^-1 for reclaimed wastewater and 0.8-4μgL^-1 for secondary effluent after 1000-fold concentration by SPE. Recoveries of nC₆₀ by LLE were in the range of 89-94% with a standard deviation (SD) not more than 2% and recoveries of nC₆₀ by SPE were much lower, only 18% for reclaimed wastewater and 9% for secondary effluent. The method detection limits (MDLs) of LLE with UV-vis spectroscopy were 3-4μgL^-1 for six water matrices and the MDLs of SPE with UV-vis spectroscopy were 0.42μgL^-1 for reclaimed wastewater and 0.64μgL^-1 for secondary effluent. UV-vis spectroscopy and mass spectrometry gave similar sensitivity. With LLE, mass spectrometry offered a small linear range of 20-60μgL^-1, but it provided specificity based on the mass-to-charge ratios (m/z) of the molecular ions. This paper demonstrates the feasibility of the combination of different extraction and detection methods to quantify nC₆₀ in engineered wastewater matrices.