2025, Vol. 7, Issue 10, Part A

Accurate trace metal analysis in petroleum products is essential for refining efficiency, catalyst protection, and environmental compliance. This study compares manual acid digestion with microwave-assisted digestion (MAD) using the Anton Paar Multiwave 7000 for analyzing trace metals (V, Ni, Fe, Al, Mo) in crude oil total blend (251-20-17 O-3) and unconverted oil fractions (UCO, 390 °C cut). Manual digestion utilized nitric (HNO₃) and sulfuric (H₂SO₄) acids under atmospheric conditions, while MAD employed HNO₃ alone or a HNO₃-H₂SO₄ mixture in a nitrogen-filled pressurized digestion cavity (PDC). Inductively coupled plasma (ICP) analysis revealed MAD’s superior performance in metal recovery and precision, with higher yields for V (2.56-6.26%), Fe (52.64-53.68%), and Al (3.84-14.95%) compared to manual digestion (V: 0.00%, Fe: 3.01-3.65%). Silicon (Si) recoveries were anomalously high (257.27-379.66%) in MAD due to contamination from borosilicate glass vials, rendering Si data unreliable. Nitrogen in the pressurized digestion cavity (PDC) suppressed boiling, prevented cross-contamination, and enabled higher digestion temperatures, reducing digestion time (115 min vs. 1-2 h) and enhancing safety. Manual digestion was labor-intensive and prone to analyte loss. These findings advocate for MAD with quartz or PTFE-TFM vials to avoid Si contamination, offering laboratories a faster, safer, and more accurate method for trace metal analysis in petroleum matrices.