Figure 4. Raman spectra of GST, ICM, GCI, and GCIP compared to published spectra of similar materials. Crystal size, in-plane, of graphite (La) ) C/(ID/IG), where C ≈ 4.4 nm. Intensities of the G′ of commercially available glassy carbon are variable and are classiﬁed as narrow and strong or nondetectable.38,39 Soot is a highly disordered graphitic structure or amorphous carbon, because it consists of graphite-like crystalline and amorphous carbon domains. So, intensities of the D, G, G′, D+G, and D′′ bands from commercially available soot depend on the completeness solid carbon conversion to CO2 and on the degree to which CO2 is converted to graphite.16 GCI and by GCIP, isotopic fractionation occurred in ICM. In addition, the Fm values of ICM (1.3355) were ∼0.4% lower than those of Ox-2 SRM (1.3407), GCI (1.3429), and GCIP (1.3410), conﬁrming prior reports.3,5 Furthermore, a large ratio of Fe/C (15:1) favored ICM formation,4,25 so by reducing the Fe/C ratio from 10:1 to 5:1, the formation of ICM was completely avoided.13 We did not ﬁnd FT-IR, Raman, or XRD spectra of AMS targets in our search of the literature, so assumed that the ICM was mostly Fe3C and some i-C or g-C rather than single graphite crystal. This observation prompted us to further investigate characteristics of AMS targets with FT-IR, Raman, and XRD. FT-IR and Raman Spectroscopy. FT-IR enabled the vibration of aromatic structures in graphite to be investigated. For FT-IR, the KBr pellet showed a good spectrum by transmission measure- ments for the aromatic structure of graphite, because FT-IR spectra are not associated with crystal structure of graphite.26 The KBr pellet produced a band ∼1630 cm-1 (H2O molecule) due to (25) Dee, M.; Ramsey, C. B. Nucl. Instrum. Methods Phys. Res., Sect. B 2000, 172, 449–453. (26) Friedel, R. A.; Carlson, G. L. J. Phys. Chem. 1971, 75, 1149–1151. 7666 Analytical Chemistry, Vol. 80, No. 20, October 15, 2008 a moisture effect, and it was partially overlapped with the ∼1580 cm-1 of the graphite band.24 The FT-IR spectra of GCI and GCIP were consistent with that of GST in Figure 3 and with those in previous reports.26,27 As shown in Figure 3, the bands at ∼1580 cm-1 for GCI and GCIP were less well resolved than the corresponding band for GST. The poor resolution suggested that GCI and GCIP might consist of i-C, g-C, or t-C; the GCI and GCIP had the appearance of disordered graphite or less ordered graphite compared to ordered graphite crystal. The FT-IR spectra of graphite showed its strong and characteristic band (∼1580 cm-1) that has been attributed to lattice vibration or “aromaticity” of the graphite and it can be identiﬁed with acoustic E1u mode including Eˆ 1u, E*1u, and E01u.26-29 The weak band of graphite, sometimes measured at 830 cm-1, was due to an aromatic impurity such as oxygen or nitrogen in graphite. Also, a-C showed two broad bands, one at (27) Smith, D. M.; Grifﬁn, J. J.; Goldberg, E. D. Anal. Chem. 1975, 47, 233– 238. (28) Tuinstra, F.; Koenig, J. L. J. Chem. Phys. 1970, 53, 1126–1130. (29) Gualberto, G. M.; Underhill, C.; Leung, S. Y.; Dresselhaus, G. Phy. Rev. B 1980, 21, 862–868.