Conventional heating vs. Microwave heating

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In addition to the acceleration of the reaction rate due to the higher temperature in closed vessels, the total time required is also influenced by the type of heating. Either classical electrical heating jackets, as used in pressure digestion vessels (e.g. digestec DAB), or microwave heating are used to heat the samples. In classical pressure digestion bombs, the heating of the sample-acid mixture takes place indirectly via the heated outer vessel. Accordingly, the heating process is more time consuming and the target temperature is usually reached after 30-60min. In the microwave, heating is achieved by direct coupling of electromagnetic radiation into the sample solution. The time to heat the samples is significantly reduced to a few minutes.  However, the kinetics of the digestion reaction, once the target temperature is reached, is the same as in conventionally heated systems.  Microwave heating only reduces the time required for the heating phase.

Typical digestion times of different digestion methods