Spectrum of PCI
The molecular peak is important for determining the molecular weight. However, an EI spectrum sometimes shows such a small molecular peak that it is hard to determine the molecular weight. Compared to an EI spectrum, a PCI spectrum shows an intense molecular-related peak with less fragmentation. Using methane or iso-butane usually produces a protoneted molecule, whose mass is M+1, where M is molecular mass. For example, the base peak of a methylstealate PCI spectrum is 239; molecular weight of methylstealate 238 plus mass of hydrogen ion 1.
![Spectrum of PCI](/an/sites/shimadzu.com.an/files/d7/ckeditor/an/support/gcms/23_4_2.gif)
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