Factorial and Doehlert designs in the optimization of a separation procedure using polyurethane foam as a solid phase extractant for platinum determination in ferrous matrices using inductively coupled plasma optical emission spectroscopy

Abstract

A procedure for separation of platinum from ferrous matrices was developed using platinum sorption as chloride complexes on polyurethane foam, with subsequent determination by inductively coupled plasma optical emission spectrometry (ICP OES). The procedure was optimized using a two-level full factorial and Doehlert designs. Four variables (foam mass, shaking time, stannous chloride concentration and hydrochloric acid concentration) were regarded as factors in the extraction optimization. Results of the two-level full factorial design, 2⁴ with 16 runs based on Analysis of Variance (ANOVA) showed that only two factors (foam mass and shaking time) are statistically significant. Doehlert design was applied in order to determine the optimum conditions for platinum separation. The proposed procedure allowed platinum determination with a detection limit of 66 μg L⁻¹ and a precision, calculated as relative standard deviation (RSD), of 1.2% in a set of 10 measurements for a platinum concentration of 10.0 μg L⁻¹. The studied procedure was applied to platinum determination in several ferrous matrices (iron ores, pure iron and catalysts). Spike tests on iron ores and pure iron showed good performance in platinum recovery. The good accuracy of the proposed procedure was confirmed by analysis of an ore platinum standard reference material (SARM-7).