Extracting Organochlorine Pesticides from Water
With Atlantic™ HLB-M Disks (EPA Method 8081)
Michael Ebitson, Horizon Technology, Inc., Salem, NH
Introduction
The purpose of this application note is to establish a solid
phase extraction (SPE) procedure to streamline the sample
preparation process for determining organochlorine
pesticides from water.
The analysis of organochlorine pesticides in water has
proved a challenging matrix to meet the data requirements
for quality control acceptance criteria’s.
Traditional
extraction methods such as liquid-liquid extraction (LLE)
or continuous liquid-liquid extraction (CLLE) can use up to
250 mL of dichloromethane (DCM) as the extracting
solvent. LLE and CLLE are labor intensive, use large
amounts of solvent, have matrix interfering emulsions, and
require contaminant free glassware to determine trace
amounts of pesticides in water. With the traditional
techniques the user still needs to interact by solvent
exchanging the extract from DCM to hexane which
involves two concentration steps with hundreds of
milliliters of solvents.
By using SPE we are able to use acetone and hexane as the
extraction solvents for the determination of organochlorine
pesticides in aqueous samples. Relative to the DCMacetone mixture, the use of hexane-acetone generally
reduces the amount of interferences that are extracted and
improves the signal-to-noise ratio within the analysis phase
of sample processing.
This was accomplished by
optimizing an SPE method based on the Horizon
Technology SPE-DEX 4790 Automated Extractor System
using a 47 mm Atlantic HLB-M extraction disk.
The pesticides analyzed in this study were part of a
standard mix consisting of alpha-BHC, gamma-BHC
(Lindane), beta-BHC, delta-BHC, heptachlor, aldrin,
heptachlor epoxide, gamma-chlordane, alpha chlordane,
4,4’-DDE, endosulfan I, dieldrin, endrin, 4,4’-DDD,
endosulfan II, 4,4’-DDT, endrin aldehyde, methoxychlor,
endosulfan sulfate, and endrin ketone. Tetrachloro-mxylene (TCMX) and decachlorobiphenyl (DCB) were used
as the extraction surrogates. Five of the pesticides (DDT,
aldrin, dieldrin, endrin, and heptachlor) are known as part
of the “dirty dozen” of persistent organic pollutants (POPs).
POPs are organic compounds that are resistant to
environmental degradation.
Pesticide pollution is a subject of global concern, and
although many countries have now banned the use of
organochlorine pesticides, they linger in the environment
and can contaminate water sources. Pesticides are toxic to
animals and humans, so methods which accurately and
easily quantify them are essential to the future.
Organochlorine Pesticide exposure can cause illnesses
including disruption of the endocrine, reproductive, and
immune systems; neurobehavioral disorders, cancer and in
severe cases even death.
Horizon Technology, Inc., 45 Northwestern Dr. Salem, NH, 03079 USA
Tel: (603) 893-3663 Fax: (603) 893-4994
The Horizon Technology SPE-DEX® 4790 Automated Extraction System,
with the Envision® Platform Controller, DryVap® Concentration System,
and the Reclaimer™ Solvent Recovery System
Instrumentation
•
•
•
Horizon Technology
-SPE-DEX® 4790 Automated Extractor System
-Envision® Platform
-Atlantic™ HLB-M 47mm disks
-DryVap® Concentrator System
-DryDisk® Separation Membranes
Agilent
-6890 GC with Dual ECD detectors
-5890 GC with 5971 MSD
Restek
-Primary Column:
Rtx-CLP1, 30m x 0.2mm ID x 0.25µm film.
-Confirmation Column:
Rtx-CLP2, 30m x 0.25mm ID x 0.25µm film.
Method Summary
Pesticide Loss Analysis on the DryVap
1)
Place six concentration tubes onto the DryVap
containing 25 mL of DCM.
2) Configure the DryVap settings as shown in Table 1.
3) Spike 20 µg of pesticide spike into each tube, then
press start on the DryVap.
4) All six spiked samples will automatically dry and
concentrate to a final volume of 1.0 mL.
5) Add internal standards then analyze by GC/MS
*Alternative Procedure: use 25 ml of hexane, then
concentrate and analyze by GC-ECD.
Pesticide Extraction
1)
2)
3)
Adjust a 1 L aqueous sample to a pH of 2 with HCL.
Cap the bottle and mix.
Spike the sample with pesticide standard and
surrogates (varying concentrations were used: 0.5
µg/L-1.25 µg/L).
Place the sealed sample bottle on the SPE-DEX 4790
Extractor System and place the Atlantic HLB-M disk,
in the disk holder.
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Extracting Organochlorine Pesticides from Water With Atlantic™ HLB-M Disks (EPA Method 8081)
4)
5)
6)
7)
8)
Run the SPE-DEX 4790 using the pesticides method
in Table 2 using acetone and hexane as the extraction
solvents
After the extraction is complete collect the extract (the
final volume should be around 25 mL).
Clean the extract using florisil.
Concentrate the extract to a final volume of 5.0 mL.
Analyze by GC/ECD.
Table 1: DryVap Conditions.
PARAMETER
Dry Volume
Heat Power
Auto Rinse Mode
Heat Timer
Nitrogen Sparge
SETTING
100
5
OFF
OFF
20 psi Vacuum @ -15 in Hg.
Table 2: Extraction Method
Step
Solvent
Soak Time
Dry Time
Prewet 1
Acetone
1:00 min
1:30 min
Prewet 2
Hexane
1:00 min
2:00 min
Prewet 3
Methanol
30 sec
2 sec
Prewet 4
Reagent Water
10 sec
0 Sec
Sample Process
Air Dry 3:00 min
Rinse 1
Acetone
3:00 min
2:00 min
Rinse 2
Hexane
3:00 min
2:00 min
Rinse 3
Hexane
1:00 min
1:00 min
Rinse 4
Hexane
1:00 min
1:00 min
Rinse 5
Hexane
1:00 min
1:00 min
Results
Concentration Results
To show the efficiency of the SPE-DEX 4790, a study was
done with the DryVap to determine the highest possible
percent recoveries that could be achieved with
concentration alone. Six DryVap tubes were spiked with
20 µg of pesticide standard into 25 mL of solvent and
concentrated to 1.0 mL and analyzed. This study was
performed to recover the selected pesticides under ideal
conditions. The result of this study is shown in Table 3.
The recoveries indicate that the DryVap alone is able to
produce great recoveries with minimal loss.
This
concentration process was fully automated, and did not
require any attention once the process was started.
Extraction Results
With the sample extracted in acetone and hexane instead of
DCM, the solvent exchange step has been eliminated. The
results shown in Table 4 below indicate that when acetone
and hexane are used as the extraction solvents, they
produced excellent recoveries on the primary column along
with the confirmation column.
Horizon Technology, Inc., 45 Northwestern Dr. Salem, NH, 03079 USA
Tel: (603) 893-3663 Fax: (603) 893-4994
Table 3: Pesticides Spike Recovery on the DryVap
Compounds
Avg.%
Recovery
a-BHC
96
b-BHC
94
g-BHC
91
d-BHC
92
Heptachlor
89
Aldrin
93
Heptachlor Epoxide
92
a-Chlordane
92
g-Chlordane
98
Endosulfan I
91
4,4’-DDE
95
Dieldrin
95
Endrin
96
4,4’-DDD
96
Endosulfan II
101
Endrin Aldehyde
100
4,4’-DDT
95
Endosulfan Sulfate
94
Methoxychlor
98
Endrin Ketone
98
Conclusions
The sample preparation step is an essential element of this
method development, as such, the advancement of an
automated disk extraction enables less solvent use, an
elimination of the solvent exchange step, reduced glassware
use, emulsion elimination, and faster extraction times with
highly particulate or sediment laden samples. This in turn
produces consistent and reproducible results.
By using Horizon Technology’s SPE-DEX 4790 automated
solid phase extraction system with the Atlantic HLB-M
disks we were able to achieve excellent recoveries of all
organochlorine pesticides. When using the HLB-M disk
the extraction process duration was about 30 minutes per
sample. Concentrating a 25 mL extract of hexane to a final
volume of 5 mL will take approximately 10 minutes with
the DryVap. Including the 10 minute sample run times on
the GC/ECD, samples were extracted, concentrated,
cleaned, and analyzed within two hours with excellent
recoveries.
Acknowledgements
Our thanks go to Sharlene Robinson from GEL
Laboratories for her time and assistance with this study.
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Table 4: Organochlorine Pesticides Recoveries
Pesticide Compounds
Alpha-BHC
Gamma-BHC ( Lindane)
Beta-BHC
Delta-BHC
Heptachlor
Aldrin
Heptachlor Epoxide
Gamma-Chlordane
Alpha-Chlordane
4,4’DDE
Endosulfane I
Dieldrin
Endrin
4,4’DDD
Endosulfane II
DDT
Endrin Aldehyde
Methoxychlor
Endosulfan Sulfate
Endrin Ketone
Tcmx
DCB
Concentration (ug/L)
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
1.25
0.50
1.25
1.25
1.25
1.25
1.25
1.25
5.00
1.25
1.25
1.00
1.00
Horizon Technology, Inc., 45 Northwestern Dr. Salem, NH, 03079 USA
Tel: (603) 893-3663 Fax: (603) 893-4994
Primary Secondary
Column
Column
CLP 1
CLP 2
Recovery% Recovery%
98
100
94
100
91
87
92
87
91
97
88
95
92
98
89
90
90
89
94
98
81
88
86
88
85
87
82
80
82
82
84
85
81
78
81
86
76
86
76
81
87
86
76
76
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