The water loss process in Laser Mass Spectrometry of amine terminal amino acids was studied. Water loss is proposed to occur via a thermal decomposition mechanism for a protonated amino acid forming a protonated lactam ring. The magnitude of the water loss peak is correlated with the stability of the protonated lactam ring. Semi-empirical MNDO calculations of the heat of reaction of a protonated amino acid forming a protonated lactam ring and water support the correlation. The substrate (matrix) appears to have little effect on the process; results are essentially the same with the use of different substrates and sample preparation methods.
BordersD. B.CarterG. T.HargreavesR. T., and SiegelM. M., Mass Spectrom. Rev.4, 295 (1985).
21.
JunkG., and SvecH., J. Am. Chem. Soc.85, 839 (1963).
22.
SrinivasR., and RamanaD. V., Org. Mass Spectrom.19, 438 (1984).
23.
YeoA. N. H. and WilliamsD. W., Org. Mass Spectrom.2, 331 (1969).
24.
McLaffertyF. W.McAdooD. J., and WitiakD. N., J. Am Chem. Soc.99, 7265 (1977).
25.
van der GreefJ. and NibberingN. M. M., Org. Mass Spectrom.14, 537 (1979).
26.
HarrisonA. G. and TsangC. W., J. Am. Chem. Soc.98, 1301 (1976).
27.
LongevialleP. G.GirardJ. P.RossiJ. C., and TichyM., Org. Mass Spectrom.14, 414 (1979)
28.
MilneG. W. A.AxenrodT., and FalesH. M., J. Am. Chem. Soc.92, 5170 (1970).
29.
DewarM. J. S. and ThielW., J. Am. Chem. Soc., 99, 4899 (1976).
30.
DewarM. J. S. and ThielW., J. Am. Chem. Soc., 99, 4907 (1976).
31.
DewarM. J. S., J. Chem. Phys.89, 2145 (1985).
32.
HeinenH. J.MeierS., and HogtH., Int. J. Mass Spectrom. Ion Phys.47, 19 (1983).
33.
MorelliJ. J.NovakF. P., and HerculesD. M., “Laser Mass Spectra Obtained at Ambient Conditions vs. Sample Freezing,” SIMS-V Fifth International Conference on Secondary Ion Mass Spectrometry, American Society for Mass Spectrometry (1985), p. 56.
34.
HerculesD. M.NovakF. P.ViswanadhamS. K., and WilkA. Z., Anal. Chem. Acta195, 61 (1987).
35.
Quantum Chemistry Program Exchange, Department of Chemistry, Indiana University, Bloomington, Indiana.
