SOME THEORETICAL CONSIDERATIONS ON THE PHYSICAL LIMITATIONS OF ATOMIC-BEAM TIME-OF-FLIGHT MASS-SPECTROMETRY

The steps essential to performing atomic beam time-of-flight (AB-TOFMS) experiments are considered. The efficiencies of vaporization, ionization and ion extraction into the TOFMS and detection are discussed in detail. Using these data, the overall responsitivity which can be expected under optimal conditions is 2E-5 detector counts per atom in the sample. This corresponds to the intrinsic limit of detection (LOD) of 5E5 atoms, a factor of 5E4 lower than experimental values reached so far. Under optimal conditions, the intrinsic LOD of AB-TOFMS is comparable to that given by the technique of inductively coupled plasma mass spectrometry (ICP-MS).