Characterisation of human hair surfaces by means of static ToF-SIMS: A comparison between Ga+ and C-60(+) primary ions

This study deals with the secondary ion yield improvement induced by using C-60(+) primary ions instead of Ga+ ones to characterize human hair surfaces by ToF-SIMS. For that purpose, a bunch of hair fibres has been analysed with both ion sources. A high improvement is observed for the detection of amino acids with C-60(+) primary ions as compared to Ga+ ions. As an example, a yield enhancement factor greater than 3000 is found for the CNO- peak. A similar gain is observed for the positive secondary ions characteristic of the amino acids. Most of the atomic ions, such as Ca+, O- and S-, constitute minor peaks with C-60(+) ions while they often dominate the spectrum in the case of Ga+ ions. However, with the C-60(+) source, a series of inorganic combination peaks with the elements Ca, S and O are observed in the positive spectra (i.e. HCaSO4+), While they are marginal with the Ga+ source. For the mass range beyond 100 m/z and in both polarities, the hair fingerprints are similar with both sources. In average, for a comparable number of primary ions per spectrum, the C-60(+) ion source gives intensities between two and three orders of magnitude higher than the Ga+ one. (c) 2006 Elsevier B.V. All rights reserved.