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Fullerenes have been detected in carbonaceous chondrite meteorites and in breccia samples from meteorite impact craters, but questions have been raised about contradictory results from similar samples and the sensitivities and accuracies of different analytical methods. We analyzed samples from three impact craters and detected C60 in samples from several locations; we also observed differences in the detection capabilities of various analytical techniques used in the search for fullerenes. The presence of C60 in rocks from the Onaping Formation of the Sudbury impact crater was confirmed. Low levels of C60 were also detected for the first time in samples from the Gardnos (Norway) and Ries (Germany) impact structures. We detected C60 in these samples using surface-enhanced laser desorption/ ionization (SELDI), but the related technique of microprobe laser-desorption, laser-ionization mass spectrometry (μL2MS) did not observe C60 above detection limits. We attribute the absence of μL2MS signal to aggregate formation caused by phthalic acid esters, which appear to easily contaminate samples either during storage or demineralization in plastic containers. The μL2MS technique is incapable of detecting aggregated C60, but aggregation does not suppress detection in SELDI. Phthalate-induced aggregation did, however, enhance SELDI detection of C60 in some cases, and we suggest that this enhancement may help explain previously reported differences in C60 detection from natural samples between laser desorption mass spectrometry (LDMS, a technique analogous to SELDI that has detected fullerenes in meteorite and impact breccia samples) and high-pressure liquid chromatography (HPLC). This work highlights the effects of phthalates and other indigenous compounds or contaminants on certain mass spectrometric techniques and lends support to the idea that several complementary analytical methods should be employed to investigate complex natural samples. |
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