Peak fitting to resolve CN − isotope ratios in biological and environmental samples using TOF-SIMS

• Published in: Applied surface science 2004-06, Vol.231, p.912-916
• Main Authors: Cliff, J.B., Gaspar, D.J., Bottomley, P.J., Myrold, D.D.
• Format: Article
• Language: English
• Subjects: ALGORITHMS; Biological; BIOLOGICAL MATERIALS; CLAYS; Environmental; ENVIRONMENTAL MATERIALS; ENVIRONMENTAL MOLECULAR SCIENCES LABORATORY; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ISOTOPE RATIO; KAOLIN; MASS RESOLUTION; Nitrogen; NITROGEN 15; Peak fitting; SHAPE; TIME-OF-FLIGHT MASS SPECTROMETERS; TOF-SIMS
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2004.03.169

Our research has focused on developing TOF-SIMS to measure organic 15 N in environmental samples [Appl. Environ. Microbiol. 68 (8) (2002) 4067]. Our goal was to develop a peak-fitting algorithm that would successfully remove the isobaric interferences of Al − and 13 C 14 N − from 12 C 15 N − ions under conditions of low mass resolution inherent in environmental samples. We tested a variety of peak-fitting models and found that the EMG+ GMG ( E+ G) model performed better than the standard peak shape shifting method under conditions of high mass resolution, unless Al − was present as an interference. Under conditions of Al − interference and low 15 N content, the standard method performed better than the E+G model. As 15 N content increased, the E+G model worked comparably or better than the standard method. Limited mass resolution during analysis of organic 15 N standards on kaolin clay dictated using the standard method which performed acceptably on standards containing greater than 1 at.% 15 N . These data emphasize the potential utility of using analytical models to resolve isobaric interferences in TOF-SIMS.