Microwave-Assisted Digestion of Alloys Coupled with Spectroscopic Determination of Manganese, Nickel, and Chromium

We present a method utilizing microwave-assisted digestion (MAD) for the dissolution of steel alloys in preparation for elemental analysis by spectroscopic techniques. Our goal is to augment traditional sample preparation procedures with an alternative method to realize improved temporal economics, reduce contact with and quantity of hazardous reagents, and introduce a modern sample preparation technique into the undergraduate analytical chemistry curriculum. A short and broadly applicable MAD temperature program was developed for an array of alloy types. Manganese, nickel, and chromium were determined spectroscopically with excellent accuracy and reproducibility using visible light (VIS), flame atomic absorption (FAAS), or graphite furnace atomic absorption (GFAAS) spectroscopy. The manganese determination (VIS) showed an average percentage recovery of 100.1% (3.3%RSD, N=27). The nickel determination (FAAS) had an average percentage recovery of 99.3% (2.4%RSD, N=27). Chromium determinations (GFAAS) yielded 95.8% (3.9%RSD, N=19) average percentage recovery. The excellent recoveries observed for the wide range of alloy types, combined with the improved sample throughput, demonstrates that MAD is a viable alternative to traditional open-beaker digestions and elemental determination of alloys in the undergraduate analytical chemistry laboratory.