Approaches to the determination of $\mathrm{C}_{60}$ and $\mathrm{C}_{70}$ fullerene and their mixtures in aqueous and organic solutions

The solvent-exchange process from toluene was used for preparing aqueous dispersions of $\mathrm{C}_{60}$ and $\mathrm{C}_{70}$ without preconcentration with final concentrations of $180\pm2$ and $62\pm1$ $\mu$M, respectively, which exceeds the previously reported maximum concentrations for $\mathrm{C}_{60}$ more than 6-fold; for $\mathrm{C}_{70}$ such an aqueous dispersion is prepared for the first time. The residual quantity of the organic solvent and low-molecular compounds determined by headspace GC-MS was not more than 1 ppb. The procedure for the determination of fullerenes in aqueous dispersions is developed using a total organic carbon analyzer and absorption spectra; LOD, 50 nM, LOQ, 200 nM by TOC. Spectrophotometric determination of fullerenes in their aqueous dispersions was optimized: for $\mathrm{C}_{60}$ at 268 nm: LOD, 0.1 $\mu$M, LOQ, 0.3 $\mu$M, for $\mathrm{C}_{70}$ at 218 nm: LOD, 0.1 $\mu$M, LOQ, 0.3 $\mu$M. RSD mixture quantification by Vierordt’s method in the range of 2 – 20 $\mu$M does not exceed 0.14 for $\mathrm{C}_{60}$ and 0.09 $\mathrm{C}_{70}$. RSD for toluene fullerene mixtures by Vierordt’s method in the range of 2 – 20 $\mu$M does not exceed 0.10 for $\mathrm{C}_{60}$ and 0.06 for $\mathrm{C}_{70}$.