Microwave Digestion: Smallest Sample Amounts

摘要

In analytical chemistry, limited sample volumes often present a challenge. If sample digestion is required prior to an analysis, the according dilution step often results in values below the determination limits of subsequent measuring methods. Even if the element contents can still be detected, the uncertainty of results is increased. For work with limited sample material, low-volume microwave systems with small surfaces are essential. Multiwave 3000 from Anton Paar with the new Rotor 64MG5 is suited for the digestion of small sample amounts (< = 20 mg) in less than 1 ml reaction solution. The 64 disposable glass vessels allow for high sample throughput and also fit directly into standard ICP autosamplers. To ensure efficient microwave digestion, a certain minimum filling volume of the digestion vessels has to be adhered to. In addition, the maximum permissible sample volume in closed systems is limited due to the pressure produced in the digestion process. This calls for a usual dilution factor between 100 and 400. If the available sample volume is also limited to a few milligrams, the dilution factor is further increased; the elemental concentrations are reduced and often fall below the determination limits of subsequent measuring methods.