Chromatographic separation and ecological risk assessment of pristine and functionalized fullerene nanomaterials in wastewater and sea water by UHPLC –UV–vis

Abstract

The broad usage of fullerenes nanomaterials and their associated toxicity to non-target organisms makes them an emerging environmental concern. Standard analytical methods to monitor their occurrence in the environment are lacking due to their unique chemical structures, which results in acute hydrophobicity leading to poor chromatographic separation. However, their environmental presence and potential environmental risks necessitate for careful monitoring and risk assessment in wastewater treatment plants and aquatic environments. In this study, a chromatographic technique using an Ultra High-Performance Liquid Chromatography (UHPLC) coupled with UV–visible detector was used for the separation and quantification of fullerene nanomaterials in wastewater and seawater. The chromatographic separation method developed focused on C60 fullerene, C70 fullerene, [6, 6]-phenyl C61 butyric acid methyl ester (C61-PCBM) and [6,6]- Thienyl- C61- butyric acid methyl ester (C61-TCBM). High resolution transmission electron microscopy (HRTEM) and ultraviolet–visible spectroscopy were used to determine the size, shape and absorption wavelength of colloidal fullerene nanomaterials. This method was used for quantification of colloidal fullerene nanomaterials in a wastewater treatment plant and aquatic environments and wastewater treatment plants to assess their risk. The percentage recoveries of fullerene nanomaterials from wastewater, tap water and sea water were investigated for all fullerene nanomaterials C61-PCBM, C61-TCBM, C60 and C70 were 84 %–108 %, 83 %–108 %, 97 %–116 % and 62 %–115 %, respectively. The fullerene nanomaterials C61-PCBM, C61-TCBM and C60 had a linear range at concentrations of 0.25 μg L⁻¹ to 50 μg L⁻¹, with linear regression of 0.9968, 0.9959, 0.9991 and 0.9914, respectively. C70 show a linear range between 0.5 μg L⁻¹ and 10 μg L⁻¹, with linear regression of 0.9914. The limit of detection for C61-PCBM, C61-TCBM, C60, and C70 were 0.0663 μg L⁻¹, 0.0262 μg L⁻¹, 0.0370 μg L⁻¹, and 0.0370 μg L⁻¹, respectively. The developed method was applied to determine the selected fullerene nanomaterials in wastewater and sea water. Their concentrations in wastewater and sea water range from not detected to 2.73 μg L⁻¹ and not detected to 2.05 μg L⁻¹, respectively. The ecological risk assessment carried out on fullerene in the investigated media was found to have no risk to medium risk.