Significant
advancement has been achieved in single-particle analysis
with the new conical ICP torch in terms of sensitivity, precision,
and throughput. Monodisperse desolvated particles of eight elements
(Na, Al, Ag, Sr, Ca, Mg, Fe, and Be) were injected into the conical
torch, and signal peak characteristics, precision, and kinetics of
atomization and ionization were investigated with optical spectrometry.
A particle introduction system was designed to ensure a smooth and
uninterrupted delivery of desolvated particles to the plasma. The
important finding is that, compared with the conventional Fassel torch,
the conical torch offers a 1.5–8 times higher peak intensity,
a 2–4 times higher peak area, a 2 times shorter peak width,
and higher precision (i.e., a 1.5 times lower RSD for peak intensity
and a 1.8 times lower RSD for peak width on average). Also, mass detection
limits were found to be similar or up to 8 times lower (i.e., 2 times
lower diameter detection limit) for the conical torch. The results
indicate that these features are due to a much higher electron density,
excitation temperature, and robustness which, together with an improved
particle trajectory, lead to rapid vaporization/atomization/ionization
of particles with minimized atom/ion cloud diffusion. Finally, the
torch was demonstrated to be capable of analyzing single particles
at a rate of at least 2000 particles per second with high sensitivity
and precision. On the basis of these results, the conical torch is
expected to bring about new possibilities in ICP-based single-particle
analysis.
