Abstract
The applicability of microwave-assisted, vapor-phase nitric acid digestion of small biological samples in closed-vessel microwave systems is examined for the inductively coupled plasma atomic emission spectroscopy (ICP-AES) determination of 10 elements (Al, As, Ca, Cu, Cd, Fe, Mn, Mo, Pb, and Zn). A 1.8 mL quartz sample container geometry was optimized for the successful decomposition of 50 to 90 mg of powdered biological samples. Microwave energy was efficiently coupled by addition of 250 μL of distilled deionized water to the sample. A single microwave-assisted, vapor-phase acid sample digestion was accomplished within 30 min (including cooling time) at ∼1200 psi pressure and 450 W microwave power in a commercial pressurized microwave decomposition (PMD) system. Multiple microwave-assisted, vapor-phase acid digestions were achieved at moderately high pressure (400 to 480 psi) and 230 °C with a second closed-vessel microwave apparatus. The results for 10 elements in biological standard reference materials agree well with the certified values.
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