1. Institute of Chemistry; University of Campinas; Campinas SP 13083-970 Brazil
2. Dempster Mass Spectrometry Group; Amazonas State University; Manaus AM 69050-010 Brazil
3. LECO Corporation; St. Joseph MI 490805 USA
4. Petróleo Brasileiro S/A; PETROBRAS, CENPES; Rio de Janeiro RJ 21941-915 Brazil