USE OF MAGNESIUM AS A TEST ELEMENT FOR INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION-SPECTROMETRY DIAGNOSTICS

To optimize the atomization and ionization processes in an inductively coupled plasma used as a source in atomic emission spectrometry, the Mg II 280.270-nm/Mg I 285.213-nm line intensity ratio is used. A theoretical ratio is calculated assuming a local thermodynamic equilibrium. A review of previously published experimental values of the ratio is given as a function of the parameters influencing the energy transfer between the plasma and the injected species. In particular, the effects of the power, the carrier gas flow-rate, the i.d. of the torch injector, the use of a sheathing gas and the presence of hydrogen are described. Values of the ratio close to the theoretical values are obtained with the use of a high power (> 1.4 kW), a low carrier gas flow-rate (< 0.6 1 min-1) and a large i.d. of the injector (> 2 mm). This optimization can also be applied to the minimization of interference effects due to the presence of sodium.