Some aspects of matrix interference caused by elements of low ionization potential in inductively coupled plasma atomic emission spectromctry

This paper deals with results of experiments performed with a 9 MHz free-running rf generator for producing an inductively coupled plasma (ICP) in argon. Samples were introduced as wet aerosols after nebulization with a concentric pneumatic nebulizer. The nett emission .signals of spectral lines emitted by Sr in the atomic as well as first ionized state were measured for volumes of plasma with projected square areas of 0.25 mm². These measurements were made while varying the observation height above the rf coil and the gas flow in the central nebulizer tube as well as adding Cs to a concentration level of 1000 μg ml^?1 to the samples.Ionic excitation temperatures were calculated and found not to be influenced by the presence of the Cs matrix. An interference induced by Cs causes an increase in both Sr atomic and ionic line intensities only in the so called preheating zone at the higher nebulizer gas flows and just above the rf coil.The Cs induced interference at these conditions results in an increase of the Sr ionic and atomic line intensity ratio, signifying a non-LTE process changing the relative population distribution of the Sr and Sr⁺ energy states.