Ca and Na interference effects in an axially viewed ICP using low and high aerosol loadings

Abstract

Ca and Na interference effects in an axially viewed inductively coupled plasma using low and high aerosol loadings were compared for a wide range of spectral lines differing in energy potentials. A simultaneous multichannel segmented charge coupled device atomic emission spectrometer was employed. Limits of detection for aqueous solutions and solutions containing 0.1% Ca and Na were determined. In comparison with the limits of detection using a cross-flow nebulizer, the mean improvement for a pure aqueous solution using an ultrasonic nebulizer was about 10-fold. However, relative to an aqueous solution, detection limits in 0.1% Na and Ca were degraded 16-10-fold for the cross-flow nebulizer and about 30-fold for the ultrasonic nebulizer. In the presence of Na and Ca at 1.35 kW, most spectral lines studied were depressed by up to 10 and 20%, respectively, using a cross-flow nebulizer. With an ultrasonic nebulizer, matrix effects were larger and both intensity enhancement and attenuation were observed, ±20-30% for Na and ±30-50% for Ca. The intensities of high energy lines were attenuated to a larger extent, whereas those for very low energy lines were enhanced, particularly in the presence of Ca. Matrix effects were reduced by up to 30% when the rf power was increased from 1 to 1.35 kW. The Mg II 280.270/Mg I 285.213 nm intensity ratio was employed to compare plasma robustness in response to high Ca and Na concentrations, mode of sample introduction and rf power changes. Ratios increased when the power was increased, but decreased when Ca and Na were present in the aspirated solutions. When the power was increased, plasma robustness increased by 20-40% when a cross-flow nebulizer was employed and 50% when the ultrasonic nebulizer was used. It was concluded that high rf power is favorable for the analysis of environmental materials.