Analysis of C60-fullerene derivatives and pristine fullerenes in environmental samples by ultrahigh performance liquid chromatography-atmospheric pressure photoionization-mass spectrometry

In this work, a method is proposed for the simultaneous analysis of several pristine fullerenes (C60, C70, C76, C78, and C84) and three C60-fullerene derivatives (N-methyl fulleropyrrolidine, [6,6]-phenyl C61 butyric acid methyl ester and [6,6]-phenyl C61 butyric acid butyl ester) in environmental samples. The method involves the use of ultrahigh performance liquid chromatography coupled to atmospheric pressure photoionization mass spectrometry (UHPLC-APPI-MS) and allowed the chromatographic separation in less than 4.5min. The product ions from tandem mass spectrometry studies of fullerene derivatives were characterized and the most abundant one (m/z 720), corresponding to [C60](-), was selected for quantitation. Selected reaction monitoring (SRM at 0.7m/z FWHM) by acquiring two transitions using both isotopic cluster ions [M](-) and [M+1](-) as precursor ions was proposed for quantitation and confirmation purposes. For pristine fullerenes, highly selective selected ion monitoring (H-SIM) acquisition mode by monitoring the isotopic cluster ions [M](-) and [M+1](-) was used. Pressurized solvent extraction conditions were optimized in order to improve recoveries of the studied fullerene compounds from sediment samples. Values up to 87-92% for C60-fullerene derivatives and lower but still acceptable, 70-80%, for pristine fullerenes were obtained. Method limits of quantitation (MLOQs) ranging from 1.5pgL(-1) to 5.5ngL(-1) in water samples and from 0.1ngkg(-1) to 523ngkg(-1) in sediments were obtained with good precision (relative standard deviations always lower than 13%). The applicability of the developed method was evaluated by analyzing several environmental samples such as sediments and pond water and the detected levels for C60-fullerene derivatives were of 0.1-2.7ngkg(-1) and 1.5-8.5pgL(-1), respectively. C60 and C70 were the only pristine fullerenes detected in the analyzed samples (0.1-7.2ngkg(-1) in sediments and 9-330pgL(-1) in water pond samples).