The application of experimental design to investigate the solvent matrix effects observed during the Determination of Rhodium (Rh) in organic media by Graphite Furnace Atomic Absorption Spectrometry (GFAAS)

摘要

In an industrial application a GFAAS method for monitoring the Rh concentration inprocess streams is being used. Matrix effects are known to exist with the application ofthis technique; in fact, it was observed that different solvents lead to different results.Therefore, standard additions have to be employed for quantitative determinations,resulting in high costs and long analysis times. In an attempt to understand theseinterfering effects, fractional factorial designs were proposed to determine whether anyGFAAS parameter was responsible for, or related to, the matrix effects. Seven GFAASparameters were investigated: final temperature, ramp time and hold time of thetransitions step (from the dry step); final temperature, ramp time and hold time of theashing/pyrolysis step; ramp time of the atomisation step. The results showed that thematrix effects were not related to any specific parameter. A complete factorial designwas implemented to demonstrate the fundamental role of the atomisation temperature.SEM analysis showed that the surface of the graphite tubes might be affected in differentways by different solvents. A Principal Component Analysis demonstrated that thematrix effects may be related to the viscosity and melting point of the solvents and maybe independent of their molar mass. To identify the origins of these effects, aninvestigation on the link between the tube surface-sample matrix interactions and thephysical properties of the matrices is recommended. Since GFAAS parameters cannotcompensate for the matrix effects, standard additions remain the preferred mode ofoperation as it accounts for the effects in-situ.