BUCHI SpeedExtractor E-916 - Manual (Page 59)

6 Operation
59 SpeedExtractor E-916/E-914 Operation Manual, Version D
6.4.7 Optimize a process
The following guidelines may help to optimize an extraction process in terms of yield and time.
Guidelines to optimize an extraction process
Action Advantage Drawback
Raising of the temperature
In general, raising the temperature increases the yield of the
extraction process. However, particularly for temperature sensitive
compounds, it is advisable to keep this parameter rather low to
prevent degradation. Generally, temperatures of 20 – 30 °C above
the boiling point provide good results. If oxidation is a concern,
degas the solvents prior to use, and close the solvent reservoir.
increased extraction
efficiency
possible degradation
and/or oxidation
Multiple extraction cycles
Extending the hold time (see section 6.2.4) enhances diffusion of
the analytes into the extraction solvent to a certain extent. However,
using fresh solvent by introducing a new cycle helps maintain a
favorable solvent/analyte equilibrium, particularly for samples that
are heavily loaded.
increased extraction
efficiency
longer total extraction
times
High pressures for wet samples
For wet samples, higher pressures often provide better results in
terms of yield and extraction efficiency. This is mostly due to better
matrix penetration of the solvent and hence faster diffusion of the
analyte from the matrix into the solvent.
increased extraction
efficiency
possible clogging of
the sample as the
sample is high in
moisture
Short extraction time (hold) for first cycle
Particularly for saturated samples, a quick first cycle is an effective
measure to prevent precipitation of the sample on the way to the
collection vials.
no precipitation in
the lines
possible additional
extraction cycle
required
Short discharge and flush times
For optimization purposes it is advisable to use long discharge
times (i.e. 3 min for E-916; 7 min for E-914) and to determine the
time needed until no more drops are collected in the vial and to let
the pressure drop to 0-1 bar. A shorter discharge time can then
be stored in the final method. A similar approach is recommended
for the flush with gas time. To speed up the flush with gas, a SKIP
button appears after a defined minimal safety period, to move on to
the final stage, given that the pressure is 0-1 bar. Shorter extraction
times none
For more detailed information about method development and optimization, please consider BUCHI's
SpeedExtractor Application booklet and BUCHI's Application and Technical Notes. Please contact
your sales person or BUCHI for these documents.