Comparative study of the determination of equilibrium dissociation temperature in inductively coupled plasma-mass spectrometry

Methods for the determination of equilibrium dissociation temperature (Tdiss) have been compared. A modified Boltzmann plot for the dissociation equilibrium of M+–O species was deemed to be the most reliable, yielding Tdiss=7172 K when the rotational constants and degeneracies of the molecular ions, and partition functions of the atomic and ionic species were taken into account. Temperatures calculated for the dissociation equilibria of individual M+–O species with dissociation energies (D0) between 2.95 and 8.91 eV yielded Tdiss values between 3970 and 5135 K. Temperatures at the low end of the range were also determined from the dissociation equilibria of species with low dissociation energies such as Al+–O (D0=1.5 eV, Tdiss=2145–2160) and Ar–O+ (D0=0.42 eV, Tdiss=3135–4426) which may indicate that these species did not equilibrate in the plasma, however, the sensitivity of Tdiss to small changes in the ion ratio resulted in a large uncertainty in the results.