The Effect of Complexity of a Matrix on Variation of Platinum Group Metal Determination Using ICP OES and Correction Method: A Spent Catalyst as a Case Study.

Recycling of platinum group metals (PGMs) from spent catalysts is a promising alternative to the sustainable metallurgy of critical metals, which requires an accurate and reliable analytical approach for their determination. A potential microwave-assisted digestion and multivariate calibration procedure was investigated to determine the PGM contents in various spent catalyst samples. The effect of several interelements (Al, Mg, Ce, and Na) was evaluated by the single factor at once and multilinear regression models, which demonstrated a significant variation in PGM determination using inductively coupled plasma optical emission spectrometry. The magnitude of effect due to these interferents can be -30% for Pt and Pd, and 20% for Rh. The application of multivariate calibration was effective for Pt and Pd determination from spent catalysts by reducing standard error of prediction from >10% to <3.5% for Pt and 8.0% to 2.6% for Pd; however, the effectiveness was more moderate for Rh. The crossed gage repeatability and reproducibility (GR&R) study showed a high value of contribution by part-to-part variation to the total variation (>98%) for all PGMs. Although the total GR&R contribution for Rh determination 19.77% was higher than those of Pt and Pd (11.03% and 8.31%), the analytical procedure was acceptable as a reliable approach. Microwave-assisted digestion and multivariate calibration showed efficient dissolution of the samples and less effects by interelements, which was suitable for investigating PGM-containing samples with a complicated matrix.