| abstract |
Methods are disclosed for ascertaining whether molecules of a particular analyte are present in a sample. Molecules from the sample are passed into an electron monochromator in which the molecules are contacted by monochromatic electrons having a kinetic energy level within a range of greater than zero eV to less than about 6 eV. These energy levels are sufficient to form ions from at least a subpopulation of the molecules by electron capture by molecules of the subpopulation. The ions formed in the electron monochromator are then passed through a mass analyzer to obtain an ion spectrum which allows a determination to be made as to whether or not the ions profiled in the spectrum include ions produced from the analyte. Thus, the disclosed methods allow greatly enhanced detection of particular analytes of interest, such as explosives, drugs, pesticides, and other compounds of environmental, security, forensic, or other concern. The methods are particularly suitable for mass analysis of anions produced by electron capture of monochromatic electrons by certain molecules entering the electron monochromator. Improvement in detection sensitivity over conventional methods is about three orders of magnitude or more with substantially improved resolution. Use of a molecule-separating device, such a gas chromatograph, upstream of the electron monochromator can provide further improvement over conventional methods. |