Determination of PAHs from
Sea Water Using Automated SPE
Brett Holmes, Horizon Technology, Inc., Salem, NH
Introduction
Polycyclic aromatic hydrocarbons (PAHs) are an important
class of environmental contaminants because of their
prevalence and demonstrated adverse health effects. PAHs are
generated in exhaust from motor vehicles and other gasoline
and diesel engines, emission from coal-, oil-, and wood burning
stoves and furnaces, cigarette smoke; general soot and smoke
of industrial, municipal, and domestic origin, and cooked
foods, especially charcoal-broiled; in incinerators, coke ovens,
and asphalt processing and use.
Some PAHs potentially cause the following health effects
when people are exposed to them at levels above the
maximum concentration limit for relatively short periods of
time: red blood cell damage, leading to anemia; suppressed
immune system. Long-term exposure is believed to potentially
lead to developmental and reproductive effects and some forms
of cancer.
PAHs released into coastal seawaters have proven to be a
prevalent problem and are thought to be responsible for the
biological effects of marine life and some human’s such as
chromosomal problems in fish and other marine organisms.
Sources of this include natural seeps, platforms, pipelines, produced
waters, vessel spills, vessel operations, aircraft dumpings, and
coastal facilities, as well as other sources.
The Horizon Technology SPE-DEX® 4790 Automated Extraction
System, Envision™ Platform Controller, DryVap™ Automated Drying
and Concentrating System, and the Oasis® HLB SPE Disk.
Instrumentation
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The Horizon Technology SPE-DEX® 4790 Automated
Extraction System provides an automated extraction of liquid
samples via SPE methods. The SPE-DEX 4790 can handle
samples ranging from 20ml to 4+L, including matrices such as
waste water and sea water. The Horizon Technology
EnvisionTM Platform Controller provides a user-friendly, webbased controller, capable of interacting with up to eight SPEDEX
4790
extractors
via
a
standard
PC.
The Horizon Technology DryVapTM Concentrator System
provides automated sample drying, with a patented PTFE
membrane technology that automatically removes residual
water from the organic solvent and concentrates each dried
extract by applying heat, vacuum, and sparge flow for up to six
samples at once. The environmentally-friendly Horizon
Technology Reclaimer Solvent Recovery System is designed to
condense and collect solvent vapors which are generated by the
DryVap Concentrator System.
These automated systems are specifically designed to
streamline the sample handling required for the preparation and
analysis of environmental samples
Horizon Technology SPE-DEXTM 4790 Automated
Extractor System
Horizon Technology EnvisionTM Platform Controller
Horizon Technology DryVapTM Concentrator System
Horizon Technology DryDiskTM Separation Membrane
Horizon Technology ReclaimerTM Solvent Recovery
System
Oasis® HLB SPE Disk (47mm)
Agilent 6890 GC with Agilent 5973 Mass Selective
Detector
o Column: DB5MS 30m x 0.25 mm ID, 0.25 um
o Flow Rate: 9 psi helium at constant flow rate
o Temp Ramp:
Temp
Rate
Hold
(°C ) (°C /Min)
(Min)
45
0
1.00
270
15
0.00
320
6.0
0.00
o Total Run Time: 24.33 min
o Injection Method:
Split, Ratio 1:10, 1.0uL injected
Temp Rate
Hold
(° C )
(°C /Min)
(Min)
280
0
0.00
Method Summary
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Sea water was collected from Salisbury Beach,
Massachusetts and transferred into 1 L sample bottles.
Samples were preserved with 1.0 ml of concentrated HCl
(pH = 2) and refrigerated.
Each sample was spiked with 50 ug of the PAHs of
interest.
Sea water was collected from Salisbury Beach,
Massachusetts and transferred into 1 L sample bottles.
_______________________________________________________________________________________________________________________________
Horizon Technology, Inc., 45 Northwestern Dr., Salem, NH, 03079 USA Tel: (603) 893-3663 Fax: (603) 893-4994
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Determination of PAHs from Sea Water Using Automated SPE
_______________________________________________________________________________________________________________________________
5)
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Samples were preserved with 1.0 ml of concentrated HCl
(pH = 2) and refrigerated.
Each sample was spiked with 50 ug of the PAHs of
interest.
Sample bottles were placed on the SPE-DEX 4790
Extractors and Oasis HLB Disks were placed in the disk
holders.
40 ml VOA vials were placed on the extractors for extract
collection.
Load the PAH method Figure 1 start the extraction
procedure.
After the extraction has completed the final extract was
removed from the extractor
The extract, now in two phases of Acetone/Water and
Methylene Chloride was poured into the Dry Disk
reservoir. The sample was dried using the DryDisk and
concentrated to 0.9 ml using the DryVap. Figure 2.
DryVap settings
Rinse the bottom of the concentrator tube with methylene
chloride and bring the extract up to 1.0 ml.
Transfer 0.4 ml of extract to a GC vial and add 8 uL of
Internal Standard.
Analysis by GC/MS
Results
All sea water samples were processed using the following SPEDEX 4790 and DryVap methods in Figure 1 and Figure 2:
SPE-DEX Automated Extraction method:
Method:
PAH
Pre-Wet #1:
Solvent – Methylene Chloride
Soak 00:30 min
AirDry - 00:15 sec
Pre-Wet #2:
Solvent – Acetone
Soak 00:30 min
AirDry - 00:15 sec
Pre-Wet #3:
Solvent – Reagent Water
Soak 00:10 min
AirDry - 00:02 sec
Pre-Wet #4:
Solvent – Water
Soak 00:10 sec
AirDry - 00:02 sec
Sample Introduction
Air-Dry Time:
00:30 min
Rinse #1: Solvent – Acetone
Soak 03:00 min
AirDry – 00:20 sec
Rinse #2: Solvent – Methylene Chloride
Soak 03:00 min
AirDry - 00:20 sec
Rinse #3: Solvent – Methylene Chloride
Soak 01:00 min
AirDry - 00:20 sec
Rinse #4: Solvent – Methylene Chloride
Soak 01:00 min
AirDry - 00:20 sec
Rinse #5: Solvent – Methylene Chloride
Soak 01:00 min
AirDry - 01:00 min
Approximate Duration:
25:00 min
Figure 1: PAH in Sea Water Extraction Method
Dry Volume:
Heat Power:
Heat Timer:
Auto rinse Mode:
20 ml
5
Off
Off
Figure 2: DryVap Concentrator Settings
The method described was based on US EPA method 8270.
After the spiked samples were prepared the collection vessel
was placed on the extractor, the Oasis HLB 47 mm Disk was
placed in the disk holder and the sample was loaded on the
extractor. The method was then started.
The SPE-DEX 4790 automatically introduces pre-wet solvents
to clean and condition the SPE disk. The samples are
processed and analytes are retained on the Oasis HLB SPE
disk. The first rinse of acetone was used to remove any trace
of added water that remained on the disk so that the methylene
chloride could fully interact with the PAH analytes.
Methylene chloride was then introduced to the disk four times
with soak times to ensure thorough interaction with the
analytes. These rinses not only elute the analytes of interest
from the disk, but also rinse the sample bottle to collect any
other residual compounds of interest from the bottle walls.
After the method was complete little handling was required.
After extraction the acetone/water layer was removed by the
DryDisk Assembly on the DryVap. The methylene chloride
phase was automatically transferred into the DryVap
concentrator tubes and immediately concentrated to 0.9 ml
using nitrogen, vacuum and heat. The concentrated extract is
then brought up to 1.0 ml and 400 uL of the final concentrated
extract was transferred into a GC vial and Internal Standards
were added. The extracts were then injected into the GC-MS
where the concentration of each PAH was analyzed.
Figure 3 shows the results for four samples. The final
recoveries of the extraction, drying and concentration process
range from 72.6% recovery on the light ends to 84.7% on the
heavy ends. Also, the relative standard deviation of each
compound was 7.0% or less. These show not only excellent
recoveries and repeatability, but also show that there is no
affect on the recoveries due to the sea water matrix.
Conclusions
The results demonstrate that the Horizon Technology fullyautomated extraction, drying and concentration systems used
with the Oasis HLB disk are capable of fully-automating
sample preparation of PAH compounds from sea water,
resulting in data that is both accurate and precise. Extraction
times were typically 20 to 25 minutes while drying and
concentration on the DryVap took approximately 35 minutes.
The Horizon Technology SPE-DEX 4790 Automated Extractor
System, coupled with the Envision Platform, DryVap
Concentrator System and the Reclaimer Solvent Recovery
System reduces analyst labor, solvent usage, turnaround time,
and greatly improves accuracy and precision.
_______________________________________________________________________________________________________________________________
Horizon Technology, Inc., 45 Northwestern Dr., Salem, NH, 03079 USA Tel: (603) 893-3663 Fax: (603) 893-4994
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Determination of PAHs from Sea Water Using Automated SPE
_______________________________________________________________________________________________________________________________
% Recoveries Compound Sample 1 Sample 2 Sample 3 Sample 4 Average RSD Napthalene 69.0% 81.3% 67.7% 72.4% 72.6% 6.1% 2‐Methylnapthalene 75.2% 83.1% 70.5% 75.2% 76.0% 5.2% Acenapthylene 80.0% 84.5% 72.5% 78.0% 78.8% 5.0% Acenapthene 78.3% 84.8% 71.7% 79.6% 78.6% 5.4% Fluorine 81.6% 85.0% 75.9% 81.9% 81.1% 3.8% Phenanthrene 82.2% 86.2% 74.6% 80.4% 80.9% 4.8% Anthracene 80.8% 82.2% 76.6% 79.9% 79.9% 2.4% Fluoranthene 83.4% 88.0% 76.6% 80.8% 82.2% 4.8% Pyrene 83.0% 87.4% 75.9% 80.0% 81.6% 4.9% Benz (a) anthracene 84.0% 86.7% 75.8% 80.7% 81.8% 4.7% Chrysene 80.9% 80.8% 74.9% 81.3% 79.4% 3.1% Benzo (b) fluoranthene 87.3% 90.1% 76.3% 77.3% 82.7% 7.0% Benzo (k) fluoranthene 80.5% 82.4% 77.6% 80.0% 80.1% 2.0% Benzo (a) pyrene 83.2% 84.3% 75.0% 77.8% 80.1% 4.4% Indeno (1,2,3‐cd) pyrene 88.4% 91.7% 78.4% 80.5% 84.7% 6.3% Dibenz (ah) anthracene 85.8% 88.1% 76.8% 78.6% 82.3% 5.5% Benzo (ghi) perylene 84.2% 86.6% 77.9% 81.9% 82.7% 3.7% Figure 3: PAH from Sea Water Recoveries
Figure 4: Chromatograph of Sea Water Sample with Spiked Compounds and Internal Standards
_______________________________________________________________________________________________________________________________
Horizon Technology, Inc., 45 Northwestern Dr., Salem, NH, 03079 USA Tel: (603) 893-3663 Fax: (603) 893-4994
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