sample digestion

Sample digestion is dissolving a stubborn solid — a rock, a leaf, a bone, a bit of plastic — by cooking it in strong acids until the whole thing breaks down into a clear liquid. Picture how a strong stew slowly dissolves a tough chunk of meat over hours of simmering; digestion does the same to materials that plain water would never touch, using heat and aggressive chemicals.

The point is to convert the analyte from a locked-up solid form into ions floating freely in solution, where an instrument can actually measure them. Many techniques — atomic absorption, plasma spectrometry — can only read liquids, so the metals trapped inside a sample must first be released into acid. Common digestion mixtures use nitric acid, sometimes with hydrochloric, hydrofluoric, or hydrogen peroxide added.

Digestion is powerful but unforgiving. The acids are corrosive and the work is often hot and pressurized; the reagents themselves can add trace contamination, and a careless digestion can boil away volatile elements like mercury or arsenic and lose them. A blank — acid run through the whole process with no sample — is essential to catch what the reagents contribute.