Derivative-Fourier transforms-polynomial fit: a coupling of interest in common non-ideal cases arises during trace metal analysis using graphite furnace atomic absorption spectrometry

Abstract

Chemometric treatment was proposed for handling graphite furnace atomic absorption (GFAAS) data. It aims at correcting the errors encountered in such a technique due to improper method parameter optimization such as: temperature of pyrolysis, absence of a chemical (matrix) modifier, slit width, concentration working range and cleaning of the graphite tube between injections. These common examples of improper method parameters optimization lead to non-ideal cases of linearity, at which the calibration curves suffer from a pronounced downward curvature. This will eventually cause a complete loss of accuracy and precision. The suggested chemometric handling of data involves the application of a derivative method to GFAA peaks followed by their convolution using 8 points sin x_i polynomials (discrete Fourier functions). The calibration data points before and after the chemometric treatment were fitted using different polynomial orders to investigate the efficiency of the proposed chemometric. Also, assessment of precision and accuracy was done to test the efficiency of the method and to check the absence of polynomial over-fitting. For comparison, the analysis was done using optimized method parameters, ideal case of linearity. For the non-ideal cases, t and F tests were applied to test the presence of significance differences in accuracy and precision results obtained before the data treatment and after the data treatment using different chemometric methods along with the different order polynomials used to fit the different calibration data.