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

Abstract

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 buthyl 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 4.5 minutes. 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 0.7 m/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 1.5 pg L-1to 5.5 ng L-1 in water samples and from 0.1 ng Kg-1 to 523 ng Kg-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 0.1-2.7 ng Kg-1and 1.5-8.5 pg L-1, respectively. C60 and C70 were the only pristine fullerenes detected in the analyzed samples (0.1-7.2 ng Kg-1 in sediments and 9-330 pg L-1 in water pond samples).