Internal standard method in flame atomic absorption spectrometry

Some selection criteria and experimental considerations for selecting an internal standard in flame atomic absorption spectrometry were studied. Rational criteria for the selection of internal standards include the atomization efficiencies of the elements. An experimental study of the variation of the atomization degree due to a temperature decrease can be made with the help of plots of absorbance against the rate at which the sample solution is introduced. The temperature decrease produced by increasing the rate at which water was introduced using a heated chamber without water-cooled condenser was estimated to vary from 2420 K to 2218 K with 1.0 ml water per minute. Curves for the alkali, alkaline earth, and several other metals were obtained in the air-acetylene flame. The shapes of the curves are critically dependent on the degree of atomization of the metal itself. Elements with curves that have similar slopes can be used as mutual internal standards. Some of the other factors which affect the atomization efficiencies—i.e. changes in fuel and air flow, and matrix composition—were also studied.