For high-throughput laboratories closed-vessel microwave digestion has some limitations.
The digestion vessels must be cleaned prior to each use (normally by a cleaning cycle in the microwave with an acid blank). The vessels must be
assembled and disassembled, which is labor
intensive, and the sample solution must
be transferred to another container prior
to analysis, which increases handling and
contamination risk. The high temperature
and pressure achieved during digestion
degrade the vessels over time, resulting in
significant consumables costs.
ensure full control of the digestion run, the
sample weight, matrix type, and acid used
must be the same for every sample in the
run. This means that a separate run must
be performed for each sample type. High-throughput laboratories that have multiple
sample types often employ several digestion systems.The Single Reaction Chamber
(SRC) technology has none of the limitations of closed-vessel digestion, and has revolutionized digestion applications.
SRC microwave digestion was introduced
commercially around ten years ago with ultraCLAVE.
The SRC is a new approach to microwave digestion. As its name suggests,
the SRC is a large, pressurized stainless
steel reaction chamber into which all
samples are placed and digested simultaneously. With SRC, the reaction vessel
in effect becomes the microwave cavity, enabling the intensity and distribution of the delivered microwave energy
to be optimized to the shape of
the reaction vessel. This ensures
even heating and therefore eliminates the need to rotate samples
during the digestion run. Because
the samples are placed inside a
pressurized vessel, individual
pressure vessels are not needed.
Aside from the reduced handling and labor
savings, a benefit of SRC over closed-
vessel digestion is that it operates at very
high temperature and pressure-up to 300
°C and 199 bar; thus complete digestion
of even the most difficult sample tvpes is
achieved. In addition, since all samples
are in the same vessel, any combination
of sample type (or weight) can be digested simultaneously.