In reply to Edmund Storms's message of Fri, 5 Dec 2008 14:49:37 -0700: Hi, [snip] > >I would like to clear up a little confusion. A mass spectrometer only >measures the mass/charge ratio of ions. These ions are made by >bombarding the gas with electrons.
Some MS use positive ions (e.g. Ar+). >This causes the molecules in the >gas to ionize and to decompose. One of the decomposition products of >most organic molecules is CH+, which is found at mass 13. This >molecule is not present in the initial gas, but is only made during >the measurement. A mass is also found at 12 which is C+, which is >also only present after ionization. The gas Mizuno has is probably a >mixture of CH4 and various complex organic molecules. If C13 is >present, it will make ions at 13, 14, 15, and 17, which result from >the ions C13+.C13H+, C13H2+, and C13H4+. These molecules will also be >seen at 12, 13, 14 and 16 in a normal spectrum based on C12. The >question people need to ask, if a lot of C13 was present, where are >the carbon-hydrogen ions based on this isotope? Note that the starting product of the experiment was phenanthrene (see http://en.wikipedia.org/wiki/Phenanthrene for a very enlightening structure diagram) which has at most 1 H atom attached to a carbon atom. IOW when you break phenanthrene up in a MS it is very likely that you will get CH+ and possibly some heavier CH combinations, such as C2H2 etc, which can't be confused with C13. However I wouldn't expect a lot of radicals with more than 1 H attached to a C. Regards, Robin van Spaandonk <[EMAIL PROTECTED]>
