2
Equipment
• Thermo Scientific
™
Dionex
™
ASE
™
350 Accelerated
Solvent Extractor system, equipped with 34 mL
Stainless Steel Extraction Cell Kit, (P/N 060071)
• Filters, Glass Fiber Cell (P/N 056781)
• 250 mL Clear Collection Bottles (P/N 056284)
• Analytical Balance (read to the nearest 0.001 g
or better)
• Mortar and Pestle (Fisher Scientific or equivalent)
• Gas Chromatograph (GC) with Electron-Capture
Detector (ECD)
Consumables, Regents and Standards
• Dionex ASE Prep Map, Moisture Absorbing Polymer
(P/N 083475)
• Thermo Scientific Dionex ASE Prep DE (diatomaceous
earth) Dispersant, 1 kg Bottle (P/N 062819)
• Sodium Sulfate
• Acetone
• Hexane
• Heptachlor
• Lindane
• Aldrin
• Dieldrin
• Endrin
• Dichlorodiphenyltrichloroethane (DDT)
All solvents are optima-grade or equivalent and are
available at Fisher Scientific.
Sample Preparation and Experimental
Conditions
Sample Preparation Using Sodium Sulfate
as the Drying Agent
The Oyster samples were prepared by blending or
chopping to produce a unifrom homogenate. 2.5 g of
the spiked oyster sample was treated with 9 g of sodium
sulfate as the drying agent prior to in-cell extraction in
the Dionex ASE 350 system. The extraction was pursued
at 100 °C using hexane:acetone (1:1) as solvents. The
extracts were analyzed by GC-ECD.
Sample Preparation Using Dionex ASE Prep MAP
as the Drying Agent
A 5 g portion of the homogenate was accurately weighed
and mixed with 1.7 g of Dionex ASE Prep DE and
1.7 g of Dionex ASE Prep MAP. Carefully transfer the
samples to the extraction cells, ensuring that the sample
is completely removed from the container. Load the
extraction cells and collection vials into the Dionex
ASE 350 system and perform the extraction according
to the conditions listed. In the case of spiked samples the
spikes were added to the sample prior to extraction.
Accelerated Solvent Extraction Conditions
Oven Temperature:
100 °C
Pressure:
1500 psi
Static Time:
5 min
Static Cycles:
3
Rinse Volume:
60%
Solvent:
Hexane/Acetone (1:1, v/v)
Total Extraction Time: 22-25 min
Results and Discussion
Sample preparation is challenging for a wet animal tissue
sample such as an oyster sample. The presence of water in
such a sample can result in poor recoveries of the analyte
of interest. A drying step is therefore needed before the
extraction. Mixtures of six OCPs at concentrations of
500 ng/g each were spiked on to the wet oyster samples.
The spiked oyster samples were mixed with Dionex ASE
Prep MAP and Dionex ASE Prep DE (1:1) or mixed
with sodium sulfate as the drying agent prior to in-cell
extraction in the Dionex ASE system. The extraction was
pursued at 100 °C using hexane: acetone (1:1) as solvents.
The extracts were analyzed by GC-ECD. The results in
Table 1 show recoveries ranging from 91% for Lindane
to 114% for DDT when the extractions are done using
Dionex ASE Prep MAP and Dionex ASE Prep DE. The
recoveries for extractions done with sodium sulfate are
considerably lower ranging from 69% for DDT to 81%
for Lindane. The data shows that Dionex ASE Prep DE
and Dionex ASE Prep MAP were an effective drying agent
for wet oyster samples with excellent recoveries for the
six OCPs. In contrast the sodium sulfate treated sample
showed poorer recoveries.
Table 1. In-cell moisture removal of oyster sample using Dionex ASE Prep MAP
and Dionex ASE Prep DE, in comparison to sodium sulfate.
Compound
% Recovery
Oyster dried with Dionex
ASE Prep MAP and
Dionex ASE Prep DE*
(n = 3)
% Recovery
Oyster dried with
sodium sulfate**
(n = 3)
Lindane
91
81
Heptachlor
93
64
Aldrin
94
66
Dieldrin
105
75
Endrin
106
70
DDT
114
69
Total
101
71
* Data is courtesy of Dr. Todd Anderson from the Department of Toxicology, Texas Tech
University, Lubbock
** In-cell drying with sodium sulfate is not recommended using accelerated
solvent extraction
