Continuum Source Atomic Absorption Spectrometry with Commercially Available Instrumentation. A Practical Solution

Abstract

Abstract A calculating method is presented in this paper which may be used to correct for the curvature of the calibration curve in atomic absorption spectrometry due to the non-absorbed light within the monochromator bandpass when a continuum source of radiation is used. Thus a linear absorbance to concentration relationship is obtained. Cu, Cr and Ca have been determined using this method with a D2 lamp as continuum source. The results agree with those obtained by the traditional method using hollow cathode lamps. The relative differences are below 6.2%. Earlier investigations concerning the use of continuum sources in atomic absorption spectrometry (aas) have shown that in some cases there are good results1–4. However, there are two problems which are difficult to overcome in continuum source aas. First, a narrow slit must be used in order to obtain a bandpass of a width equivalent to the absorption line. However, in this case the light intensity transmitted to the monochromator and arriving to the detector is so small that the detection limits will be very poor. Of course the transmitted intensity may be increased if a wider slit is used. But in this case, the non-absorptive part on the two sides of the absorption line will also enter the monochromator and fall on the detector. As a result the sensitivity will be degraded and the calibration curve will bend towards the concentration axis. Problems such as those discussed above prevented the current use of continuum source aas. The whole field has been recently reviewd extensively4a. In this paper we consider a calculationg method which can overcome the influence of non-absorbed radiation and can also correct the non-linearity of the calibration curve. In the first part of the paper the calculating method is introduced and in the second part some factors affecting the method are discussed and the comparaison of some results obtained by this method and the traditional method are given.