Methods of calibration in the direct analysis of solid samples by electrothermal atomic absorption spectrometry

One of the major problems involved in the direct analysis of solid samples by electrothermal atomic absorption spectrometry (ETAAS) lies in the calibration step because non-spectral interference effects are often pronounced. Three standardization techniques have been described and used in solid sampling-ETAAS: (i) standard additions method; (ii) calibration relative to a certified reference material; and (iii) calibration curve technique. However, an adequate statistical evaluation of the uncertainty in the analyte concentration in the solid sample is most frequently neglected, and reported errors may be seriously underestimated. This can be attributed directly to the complexity of the statistical expressions required to accurately account for errors in each of the calibration techniques mentioned above, and the general lack of relevant reference literature. The object of this work has been to develop a computer package which will perform the necessary statistical analyses of solid sampling-ETAAS data; the result is the program “SOLIDS” described here in the form of an electronic publication in Spectrochimica Acta Electronica, the electronic section of Spectrochimica Acta Part B. The program could also be useful in other analytical fields where similar calibration methods are used. The hard copy text, outlining the calibration models and their associated errors, is accompanied by a diskette containing the program, some data files, and a manual. Use of the program is exemplified in the text, with some of the data files discussed included on the diskette which, together with the manual, should enable the reader to become familiarized with the operation of the program, and the results generated.