| Popis: |
Ions can be selectively rejected from the r.f.-only collision cell of a tandem quadrupole mass spectrometer, using an auxiliary r.f. field tuned into their characteristic transverse frequency. The efficiency of this method was studied on a mixture of Fe(CO) + n ions ( n = 0–5, m/z 54–196) confined (0.5 ms) in the collision cell. Optimization of r.f. power allowed almost complete rejection of the 56 Fe + ion (at an intensity equal to 2.5% of its initial value) with no distortion of other Fe(CO) + n ions, and with only a slight intensity decrease of the minor isotope, the 54 Fe + ion (at an intensity equal to 75% of its initial value). The rejection efficiency was also determined as a function of the frequency of the auxiliary r.f. field. The rejection technique was applied to reaction mechanism elucidation in the case of the reaction between Fe + ions and allyl chloride. Upon rejection of one of the product ions (C 3 H + 5 , m/z 41), a large intensity decrease was also observed for some other product ions (e.g. C 6 H + 9 , m/z 81; C 6 H + 7 , m/z 79), indicating that these ions are produced from further reactions of the rejected ion. |
