Figure 3

APPI (besides APCI) proved very useful technique for the analysis of non-polar compounds like hydrocarbons. Also, in positive ion mode APPI was the most efficient method to ionize compounds such as C_aH_bN₂S₂O_x, C_aH_bN₂SO_x and C_aH_bN₂O_x. However, using APPI in positive ion mode one has to take into account that [MH]⁺ as well as [M]⁺ ions are detected.⁴

Figure 4

Table 1: Molecular formulae identified by different ionization methods.

Conclusion

We demonstrate the use of ultrahigh accurate mass measurements in combination with automated elucidation of molecular formula. Only the combination of different ionization techniques and ultra high resolution mass spectrometry gives utmost insight into complex mixtures such as crude oil, which are not readily resolved by chromatographic strategies. In addition, selectively enhancing certain mass areas by means of CASI reveals low abundant species.

Therefore, ESI-, APCI-and APPI-FTICR mass spectrometry are very important and complementary tools for the rapid analysis of crude oil.

References

1. A.G. Marshall, Energy and Fuels, 15, 492 (2001).

2. R.P. Rodgers et al., Anal. Chem., 77, 21A (2005).

3. A.G. Marshall et al., Acc. Chem. Res., 37, 53 (2004).

4. J.P. Purcell et al., Anal. Chem., 78, 5906 (2006).

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