COMPARISON OF IONIC LINE-BASED INTERNAL STANDARDIZATION WITH AXIALLY AND RADIALLY VIEWED INDUCTIVELY-COUPLED PLASMA-ATOMIC EMISSION-SPECTROMETRY TO COMPENSATE FOR SODIUM EFFECTS ON ACCURACY

A comparison was conducted to verify the efficiency of internal standa rdization as a function of the observation mode in ICP-AES to compensa te for the matrix effects on accuracy due to the presence of Na. An IC P system that allowed the use of either the radial or axial viewing mo de was used. Operating conditions, i.e., power and carrier gas flow ra te, were selected so as to obtain so-called robust and non-robust cond itions. Robust conditions corresponded to a residual depressive effect due to the aerosol transport and filtering. The concentrations of tes t elements were determined based on the use of calibration graphs cons tructed with solutions that did not contain Na, while the elements wer e in solutions containing 10 g l(-1) of Na. Because only ionic lines e xhibited a similar behavior, different ionic lines were used in order to cover a large range of ionization and excitation energies. A single internal standard was used, based on the Ni II 231 nm line. The resul ts confirmed that efficient infernal standardization was obtained when robust conditions and radial viewing mode were used. A slight degrada tion of the internal standardization efficiency was observed when the axial viewing mode was used. Conclusions about possible matrix mismatc hes are given and exemplified.