The Extraction Procedure
— 2 — To perform an extraction, for example, using a Soxhlet extraction apparatus, the following equipment, accessories and expendables are needed: Accessories and Expendables Stock Number: Evaporating dish, 70 mm diam., glass
QL9000113
Beaker, 100 ml
VG1121116241
Desiccator, DN 150 (for a single extraction)
QL9042031
with desiccator plate
QL9042514
Desiccator, DN 300 (for multiple extractions)
QL9042047
with desiccator plate
QL9042528
Homogenizer with stand, clamps and accessories
QL9571195
Analytical balance with 0,001 accuracy, for example QL6250429 Plastic spatula / spoon combination
80596
Drying oven Extraction thimbles for the 100 ml Soxhlet
VG804841034
Boiling chips
VG804830700
Silica gel, 1 kg
CBKIESELGEL1L
Cotton, 400 g
QL9413151
Extraction solvent, for example Petroleum ether; boiling fraction 40 – 60 °C Sodium sulfate, anhydrous Sand
Equipment Stock No.
Model
No. of samples
Control of heating power
Time-Temp. Control
804800522
KEX 100 F
1
X
–
804880023
In-line heating unit R 104 S
4
Individually for each sample
–
804880022
In-line heating unit R 106 S
6
Individually for each sample
–
Heating block system 804850020 804850025
DET (DBAS + DFE 100)
X
— 3 —
Preparation for the Extraction
Place 3 or 4 boiling chips into the solvent vessel (e.g round bottom flask or cylindrical flask).
Dry the solvent vessel in a drying oven to constant weight (about 1 hour) at 103±2 °C
Fill the silica gel into the desiccator and insert the desiccator plate.. Allow the desiccator to cool to room temperature (about 30 minutes).
— 4 —
Weigh the solvent vessel containing the boiling chips to an accuracy of ±1 mg.
Sample Preparation
Homogenize or grind the sample.
— 5 —
Ground sample
dry
0.000
ON OFF
TARE
weigh
moist
0.000
ON OFF
liquid
TARE
weigh
weigh
dry
mix
wipe
cover
extract
drain
— 6 —
Dry Samples
Weigh the ground dry sample into the extraction thimble. For example, weigh out 6.6 g with an expected fat content of at most 2 g.
Moist Samples
Moist samples must be dried for 2 – 3 hours at 103±2 °C in a drying oven after having been weighed in the extraction thimbles.
Liquid Samples Containing Water Content
Weigh the liquid sample into an evaporating dish
— 7 —
Mix the liquid sample with sand and anhydrous sodium sulfate.
Use a cotton swab, which has been moistened with extraction solvent, to wipe the sample into the extraction thimble.
Extraction Close the extraction thimble with a fat-free cotton wad Insert the thimble into the Soxhlet extractor If the Soxhlet extractor has a spigot for solvent draining, close the spigot.
— 8 —
Fill the solvent into the solvent vessel. Extract at a temperature of 110-130 °C for 20 – 30 extraction cycles (4 – 6 hours), depending on the nature of the sample and the solvent employed.
— 9 —
Drain the solvent into a suitable container by opening the spigot on the Soxhlet extractor. Continue to heat the solvent vessel until all of the solvent has been evaporated and condensed in the Soxhlet extractor (spigot closed). Care must be taken not to heat the fat residue to decomposition. The thus recovered solvent may be reused for subsequent extractions.
— 10 — Place the vessel containing the fat residue in a drying oven at 103±2 °C and heat to constant weight (indicating evaporation of all solvent. After every completion of the solvent evaporation step, air the drying oven out by leaving the door open. Observe carefully all safety guidance of the oven manufacturer.
Allow the vessels containing the fat to cool to room temperature (about 30 minutes).
— 11 —
Weigh the vessel containing the boiling chip and fat residue. Compute the fat content according to the following formula: F [%] =
m 2 − m1 • 100 where E
m1
is the weight of the dry empty vessel, in grams, including the boiling chips,
m2
is the weight of the vessel, in grams, containing the boiling chips and fat residue after evaporation of the solvent and
E
is the sample weight in grams.
behr Labor-Technik GmbH • Spangerstraße 8 • D – 40599 Düsseldorf/Germany Tel. +49 (0)211 748 47 17 • Fax: +49 (0)211 748 47 48 • email:
[email protected] • http://www.behr-labor.com
