IR determination of toluene impurity in fullerenes C-60 and C-70

Simple IR-analytical method is proposed to determine the small toluene contamination in fullerenes. It consists in measuring the absorbance of toluene band at 728 cm(-1). Solid samples of C-60, C-70 and their mixture were analysed in KBr pellets, and as solutions of C-60 in CS2. Quantitative determination of toluene content was based an calibration found using the absorbance of weighted fractions of toluene in carbon disulfide, cyclohexane and tetrahydrofurane solutions. The precision and limitations of the procedure are discussed. 0.5-3 mole per cent of toluene were found in some commercial samples certified as ''99 mole per cent pure C-60''. The method was shown to be applicable to benzene contamination as well.