Application of two- level full factorial designs and response surface methodology in the optimization of the variables associated with the determination of platinum using inductively coupled plasma –atomic emission spectrometry (ICP – AES)

Abstract

In the present work, two -level full factorial designs and response surface methodologies were applied in the optimization of variables associated with the determination of platinum using Inductively Coupled Plasma –Atomic Emission Spectrometry (ICP-AES). The four variables, carrier gas flow rate, pump speed, plasma observation height and plasma power were regarded as factors in the optimization process. The analysis of variance (ANOVA) and a p-value significance level of 0.05 followed by the Pareto chart of standardized main and interaction effects were used to assess the significance of the factors on the response, i.e. platinum intensity. The main effects of carrier gas flow rate and plasma power and the interaction effect of carrier gas flow rate and plasma power were found to be statistically significant. The procedure was optimized using contour maps and response surface methodology. Plasma observation height and pump speed were found to have an insignificant effect on the platinum intensity. The recommended optimized procedure comprised the following levels for the variables: carrier gas flow rate of 0.70L/Min and plasma power of 1400W. Plasma observation height of 10mm above the load coil and a pump speed of 30 revolutions per minute were adopted from recommendations of other researchers. The optimized procedure was validated by analysis of Certified Reference Materials (CRMs) i.e. AMIS 0132 for low platinum grades and AMIS 0164 for high platinum grades. The precision was determined by analysis of a concentrate composite solution. The performance characteristics or analytical figures of merit for the optimized procedure were determined and the procedure was found to be fit for the intended purpose, i.e., the determination of platinum in both low grade and high grade samples like ores, tails, feeds and concentrates for metallurgical processes.