Agriculture Reference
In-Depth Information
Figure 7.3.
Solutions obtained by Soxhlet and magnetic stirring of soil with either water or
hexane.
while the magnetic stirred extract is cloudy even after being filtered 2 times.
All three solutions have ultraviolet absorptions as a result of components
extracted from the soil [21].
7.4.3.
Ultrasonic Extraction
Ultrasonic extraction or sonication involves disruption and mixing a sample
and extractant using
ultrasound
, which is sound above the hearing range of
approximately 10,000 Hz. A high-frequency electrical current is applied to a
piezoelectric crystal that causes a metal tip attached to it to oscillate at high
frequency. This produces a series of compressions and relaxations in the
extraction mixture, causing disruption and mixing in the extraction vessel. A
typical ultrasonic “horn” is shown in Figure 7.4. A complete ultrasonic extrac-
tion setup involves both the “horn” and a high-frequency source [7,22].
7.4.4.
Microwave-Assisted Extraction
Caution
:
Microwave-assisted extraction must always and only be
carried out in microwave ovens and digestion containers, with appro-
priate sensors, especially designed for this purpose.
Microwave-assisted extraction involves sealing a sample and extractant in a
special microwavable digestion container, placing it in a special microwave
