Case 1: #
Goal: To Evaluate the efficiency of various extraction methods and solvent systems
Extraction methods and solvent systems to be compared:
There are eight methods for comparison.
1) Two extractions + SPE
LLE extraction
Pre-extraction solvent: hexane:ethanol (2:1). 16 hours stand
Extraction solvent: methanol:chloroform(1:1)
SPE cleanup
4 inch Florisil column.
Eluting solvent: 200mL of 15% diethyl ether in pentane.
2) Two extractions + SPE
LLE extraction
Pre-extraction solvent: hexane:ethanol (2:1). 16 hours stand
Extraction solvent: methanol:chloroform(1:1)
SPE cleanup
4 inch Florisil column.
Eluting solvent: 200mL of 20% methylene chloride in petroleum ether.
3) One extractions + SPE
LLE extraction
Pre-extraction solvent: N/A
Extraction solvent: methanol:chloroform(1:1)
SPE cleanup
4 inch Florisil column.
Eluting solvent: 200mL of 15% ethyl ether in pentane.
4) Two extractions + SPE
LLE extraction
Pre-extraction solvent: N/A
Extraction solvent: methanol:chloroform(1:1)
SPE cleanup
4 inch Florisil column.
Eluting solvent: 200mL of 15% ethyl ether in pentane.
Procedures:
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Sample was homogenized.
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2-5 replicates were tested.
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The means and their standard deviations were calculated for evaluation.
Reference:
Evaluation of Extraction and Cleanup Methods for Analysis of DDT and DDE in Green Alfalfa, 1968,
PMID: 24185325 DOI: 10.1007/BF01558356
Case 2: #
Goal: to evaluate the efficiencies of extraction methods and clean-up method for PAH in peat samples
The first aim of this study was to compare the extraction yields of ASE, FBE and USE for the determination of PAH in peat samples.
The second aim of this study was to evaluate other methods for sample clean-up in order
to improve the chromatographic separation and quantification of PAH.
Peat sample were dried, ground, homogenized, and stored.
Three deuterated PAH were used to determine the recovery rate because there would have PAH in peat samples. Mean and SD of each compound under three extraction methods were calculated.
Compare: 1) Ultrasonic extraction (USE); 2) Fluidized bed extraction (FBE); and 3) Accelerated solvent extraction (ASE). In order to compare three extraction methods, all extracts were cleaned up with the same clean-up method.
To compare cleanup procedures, all samples were extracted with the same extraction method - ASE. Two replicates were analysis per clean-up method. Three clean-up methods were compared. Bar plots were used, no statistical analysis were done.
The conclusion: The results of this study show that the selection of an appropriate extraction technique should not be based on the determination of recoveries of internal standards only.
This conclusion is not backed up by ANOVA. There is no evidence on significant difference among three extraction methods.
Reference:
Evaluation and optimization of extraction and clean-up methods for the analysis of polycyclic aromatic hydrocarbons in peat samples, 2005,
DOI:10.1080/03067310500140352