Desirability approach for optimisation of electrothermal atomic absorptionspectrometry factors in iron determinations

We report here on iron determination in sea matrix by electrothermal atomic absorption spectrometry. We optimised the experimental conditions of the s pectroscopic factors, i.e. entrance monochromator slit height, slit width a nd lamp current, and of the electrothermal factors, i.e. calcination temper ature, calcination duration, atomisation temperature and injected volume, s ince these two groups are independant. Because of the technical constraints occuring on our experimental domain of study we built a D-optimal experime ntal design to conduct these optimisations. We monitored three optimisation s. We monitored three experimental responses, i.e. the standard deviation o f the instantaneous specific absorbance, the specific integrated absorbance and the non-specific integrated absorbance. The three of them clearly show ed an optimum in three opposed experimental conditions. Consequently a desi rability transformation of the experimental responses permitted us to obtai n a better compromise. We, finally, computed a new experimental response wh ich took the raw measurements into account to directly estimate the limits of detection. The optimisation of this computed response showed us that the lowest detection limit was obtained under the same experimental compromise than the one suggested by the desirability study. This result allowed us t o validate the computed response as an interesting optimisation spectrometr y.