The document discusses the Soxhlet extraction method, an important process for extracting chemical constituents from plant materials using hot organic solvents. It describes the design and functioning of the Soxhlet extractor, which consists of a percolator, thimble, and siphon, allowing for continuous extraction and recycling of solvents over extended periods. Although efficient, the method has drawbacks such as long operation times and the need for solvent evaporation after extraction.

1. Soxhlet Extraction
By: Anupriya Singh
Ph.D. Scholar
Department of RSBK, Faculty of Ayurveda
Institute of Medical Sciences, Banaras Hindu University

2. Extraction
 Extraction is the first step in the analysis of plant constituents.
 It is a process of removing or taking out or separating the chemical
constituents from the plant tissues with or without the use of solvents.
 Various methods of extraction are available for this process/extraction.
 The particular method of extraction to be used depends on the:
o Nature of the constituents
o Type of the plant material
o Purpose of the extraction.

3. Soxhlet extraction
 Soxhlet extraction is a continuous process of extraction with a
hot organic solvent.
 Typically, Soxhlet extraction is used when the desired
compound has a limited solubility in a solvent, and the impurity
is insoluble in that solvent.
 It allows for unmonitored and unmanaged operation while
efficiently recycling a small amount of solvent to dissolve a
larger amount of material.

4. Soxhlet extractor
 A Soxhlet extractor is a piece of laboratory apparatus, invented
in 1879 by Franz von Soxhlet.
 A Soxhlet extractor has three main sections:
 A percolator (boiler and reflux) which circulates the solvent.
 A thimble (usually made of thick filter paper/cotton) which
retains the solid to be extracted.
 And a siphon mechanism, which periodically empties the
thimble.

5. Assembly
 Thimble: The source material containing the compound to be
extracted is placed inside the thimble. The thimble is loaded
into the main chamber of the Soxhlet extractor.
 Distillation flask or Round Bottom Flask (RBF): The
extraction solvent to be used is placed in a distillation flask.
 Heating mantle: The flask is placed on the heating element.
 Reflux condenser: A reflux is placed atop the extractor.
 Water inlet & outlet: Attached in the inlet & outlet opening of
condenser.

6. Working procedure
 Solid material placed in thimble.
 Soxhlet extractor is placed onto a flask containing the extraction solvent.
Soxhlet equipped with a condenser.
 The solvent is heated to reflux.
 The solvent vapour travels up a distillation arm and floods into the
chamber housing the thimble of solid.
 Solid material in chamber slowly fills warm solvent.
 Desired compound dissolves in the warm solvent.
 When the Soxhlet chamber is almost full, the chamber is emptied by
the siphon. The solvent running back down to the distillation flask.

7. Cont…
 This cycle may be allowed to repeat many times, over hours or
days.
 During each cycle, a portion of the compound dissolves in the
solvent.
 After many cycles (72 hours) the desired compound is
concentrated in the distillation flask.
 After extraction the solvent is removed, typically by means of a
rotary evaporator, yielding the extracted compound.
 The non-soluble portion of the extracted solid remains in the
thimble, and is usually discarded.

8. Advantages
 It is mechanically gentle on the samples but still efficient in
separation.
 It is able to extract solute from insoluble impurities.
 It is often used as a benchmark when developing new extraction
methods.
 It allows for unmonitored and unmanaged operation.
 It is the most useful apparatus for solid-liquid extraction in
various fields such as pharmaceutics, environment, foodstuffs
etc.

9. Disadvantages
 Long operation time required (several hours).
 Large solvent volumes.
 Evaporation and concentration needed at the end of the
extraction.
 Inadequacy for thermolabile analytes.

10. Advancement
 Focused Microwave-assisted Soxhlet Extraction: Microwave-
assisted soxhlet extraction is a process in which two sources of
energy, namely microwaves (applied on the extraction chamber
of a modified Soxhlet) as auxiliary energy to accelerate the
process and electrical heating (applied on the distillation flask).
Ex. Fat extraction from prefried and fried meat, fish &, bakery
products etc.

11. Conclusion
o Extraction is essential for isolation of different chemical
constituent from crude drug material.
o Extraction depends on properties of material to be extracted.

12. References
1. Harwood, Laurence M.; Moody, Christopher J. (13 Jun 1989). Experimental organic chemistry: Principles and
Practice (Illustrated ed.). Wiley-Blackwell. pp. 122–125. ISBN 978-0-632-02017-1.
2. Soxhlet, F. (1879). "Die gewichtsanalytische Bestimmung des Milchfettes". Dingler's Polytechnisches Journal (in German). 232: 461–
465.
3. Jensen, William B. (December 2007). "The Origin of the Soxhlet Extractor". Journal of Chemical Education. 84 (12): 1913–
1914. Bibcode:2007JChEd..84.1913J. doi:10.1021/ed084p1913.
4. Cumpson, Peter; Sano, Naoko (February 2013). "Stability of reference masses V: UV/ozone treatment of gold and platinum
surfaces". Metrologia. 50 (1): 27–36. Bibcode:2013Metro..50...27C. doi:10.1088/0026-1394/50/1/27. The apparatus we propose for
the solvent pre-wash is the Soxhlet apparatus, which has been used very successfully before for washing stainless-steel standard-mass
surfaces. This apparatus has its main application in chemistry for dissolving weakly soluble species from solid matrices

13. Thank you