Page 103 - Inorganic Mass Spectrometry : Fundamentals and Applications

I~ductively Coupled Plas~a Mass Spectro~et~ 93

mass. Reaction product ions could produce new spectral overlaps, They could also
react further through a series of reactions to produce other potentially interfering
background ions.
Collisional fragmentation cells have been used in triple quadrupole MS-MS
instruments for organic mass spectrometer for some time. However, scattering
be
losses of Ce+ analyte ions in ICP-MS were found to greater than the reduction
in the CeO+ signal. It is unlikely that collisional fragmentation will be effective
for reduction of spectral overlaps in ICP-MS.
[ 1 1 l] showed, using
Ion-molecule reactions can be very efficient. Douglas
ICP-MS-MS, that Ce0,+ could be formed in a reaction cell with the addition of
oxygen. Rowan and Houk [ 1121, using a double-qua~pole instrument, demon-
strated that hO+, hN+, and h,+ signals were reduced more rapidly than some
et
al. [ 1 131
of the elemental ions when Xe CH, was used as a reaction gas. Eiden
or
were able to reduce the h+ signal by six orders of magnitude by adding H, to an
ICP-ion trap mass spectrometer.
Turner et al. [l 14.1 described an ICP-MS with a hexapole transfer lens (Fig.
3.12a) in a tube that allows the pressure to be maint~ned. The cell was initially
reported to contain He, although it is likely that H, or H,O vapor was also in the
cell and is now purposely added to the cell [ 1 151. h,+, ArCl+, ArO+, and Ar+
signals were reduced relative to Se+, As+, Fe+, and Ca+, respectively. Detection
limits for Fe, Ca, K, Se, and As near 10 parts per trillion (ppt) have been reported
[ 1 151. Recently, Beaty and Liezers 1 161 also described a collision-reaction cell at
[
a pressure of 30 mtorr that reduced the ion kinetic energy spread as well as
“continuum” ICP-MS background to less than 1 countlsec. Previously, Douglas
of
and French had described the use an rf-only quadrupole for collisional focusing
and reduction of the ion kinetic energy spread [l 171.
Recently, Tanner et al. [ 1 18- 1201 described a quadrupole reaction cell they
have termed a dy~a~ic reaction cell (DRC) used with a quadrupole mass spec-
trometer (Fig. 3.12b). Reactive gases, such as NH,, H,, 0,, and H,O, were
to
investigated, Charge transfer or proton transfer reactions could be used advan-

(a) ICP-MS with hexapole collision-reaction cell similar to that used by
Micrornass. (b) ICP-MS with dynamic reaction cell as described by Perkin- ,Elmer Sciex.