Analysis of Polynuclear Aromatic Hydrocarbons Using US EPA Quick Turnaround Method (QTM) with the Empore™ C18 SPE Disk
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Authors: Guotao Lu
Study summary: A validated solid-phase extraction (SPE) workflow using the CDS Empore™ 47 mm C18 SPE Disk extracts 16 PAHs from 100 mL aqueous samples per the U.S. EPA Quick Turnaround Method (QTM). After methylene chloride elution, anhydrous sodium sulfate drying, and nitrogen concentration to 1.0 mL, PAHs are quantified by GC-FID. Validated in groundwater from hazardous waste sites at two spike levels: 200 ppb (n=6, average RSD 5.9%) and 20 ppb (n=3, average RSD 6.2%), with the 7 EPA-classified carcinogenic PAHs all exceeding 87% recovery at the 20 ppb level.
TL;DR: The U.S. EPA Quick Turnaround Method (QTM) is a streamlined SPE-based workflow for rapid PAH screening in water — designed for environmental and drinking water labs that need fast turnaround over the deeper sensitivity of EPA Method 525.2. The Empore™ 47 mm C18 SPE Disk extracts 16 PAHs from a 100 mL water sample, processes faster than traditional packed-bed cartridges, and delivers average RSD 5.9% / 6.2% across two spike levels. Recoveries for the 7 EPA priority carcinogenic PAHs are consistently above 87% at the 20 ppb level — meeting the sensitivity requirements for hazardous waste site groundwater monitoring.
Study at a Glance
Introduction: PAHs and Public Health
Polycyclic aromatic hydrocarbons (PAHs) are well-known as one of the most hazardous organic pollutants to the environment. PAHs are defined as a group of over 100 different compounds with fused aromatic rings and are normally formed during the incomplete burning of carbon-based fuels (wood, coal, diesel, oil and gas, and other organic compounds), as well as directly residing in crude oil, rubbers, plastics, lubricants, paints, leather, and other products.
Because of the toxicological significance of seven specific PAHs (listed in the section above), PAHs need to be closely monitored in environments, especially in drinking water to ensure public safety. Environmental laboratories rely on rapid, validated SPE-based extraction methods to keep up with the high volume of regulatory and screening samples processed daily.
This application note demonstrates a simple but effective method to extract PAHs from large-volume water samples (100 mL) using a 47 mm C18 CDS Empore™ disk and elution with methylene chloride. The extract is then concentrated and analyzed by GC-FID. If interfering compounds are present in real-world samples, the cleanup protocols described in the EPA QTM method can be applied before GC-FID analysis.
Headline performance:
16 PAHs covered in a single workflow (15 native + 1 surrogate)
Validated at 2 spike levels: 200 ppb (n=6) and 20 ppb (n=3)
Average RSD 5.9% / 6.2% across the 16 compounds at both levels
All 7 EPA priority carcinogenic PAHs > 87% recovery at 20 ppb level
Real-world validation in groundwater from hazardous waste sites
Why the Empore™ C18 Disk for EPA QTM PAH Analysis
The CDS Empore™ 47 mm C18 SPE disk demonstrates significant advantages over traditional packed-bed SPE cartridges for large-volume aqueous sample analysis under the EPA QTM workflow:
Faster sample throughput — the disk format processes 100 mL of water faster than packed-bed cartridges, supporting the "Quick Turnaround" design intent of the QTM method
No channeling effects — the membrane sorbent gives uniform flow and consistent PAH retention sample-to-sample, eliminating variability seen with packed-bed cartridges
Lower elution solvent consumption — the thin disk geometry requires less methylene chloride to elute fully, reducing solvent costs and nitrogen concentration time
Suitable as an environmental screening tool — the disk-based QTM workflow is validated for environmental testing labs analyzing PAH concentrations in aqueous samples for routine screening
Compatible with manifold processing — multiple disks can be run simultaneously on a manifold for batch sample throughput
Materials
SPE Media
CDS Empore™ 47 mm C18 SPE Disk — primary extraction medium
Glassware & Apparatus
All-glass filtration assembly (47 mm format)
Manifold (optional, for multiple parallel extractions)
Concentrator tube
Sample collection tube
Disposable pipette
Solvents & Reagents
Methylene chloride — primary elution solvent + apparatus prewash
Methanol — disk conditioning + 0.5 mL added to each water sample as wetting agent
Acetone — pre-elution wetting (~0.5 mL or less)
Reagent water — disk equilibration
Anhydrous sodium sulfate — eluate drying agent
Nitrogen gas — for eluate concentration to 1.0 mL
Detection Platform
Note on instrument parameters: The original application note focused on extraction performance using the Empore™ C18 disk. Detailed GC-FID instrument parameters (capillary column, temperature program, FID settings) follow the directions specified in the official U.S. EPA Quick Turnaround Method (QTM) publication. Parameters explicitly stated in this validation work are summarized below.
Validated EPA Quick Turnaround Method Extraction Procedure
1. Filtration Apparatus Assembly
Assemble an all-glass filtration assembly using a 47 mm C18 Empore disk. Use of a manifold for multiple extractions is acceptable.
2. Apparatus & Disk Prewash
Wash the extraction apparatus and disk by adding 5 mL of methylene chloride to the reservoir. Pull a small amount through the disk under vacuum, turn off the vacuum, and allow the disk to soak for about one minute. Pull the remaining solvent through the disk and allow the disk to dry.
3. Disk Conditioning
Condition the disk by adding approximately 5 mL of methanol to the reservoir. Pull a small amount through the disk, then let it soak for about one minute. Pull most of the remaining methanol through, leaving 3–5 mm of methanol on the surface of the disk.
4. Disk Equilibration
Add 10 mL of reagent water to the disk. Using vacuum, pull most through, again leaving 3–5 mm of water on the surface of the disk.
5. Sample Loading
Add 0.5 mL of methanol to the 100 mL water sample and mix well. Add the water sample to the reservoir and, under vacuum, filter as quickly as the vacuum will allow. Drain as much water from the sample bottle as possible.
6. Disk Removal & Tube Insertion
Remove the filter assembly and insert a suitable sample tube for eluate collection.
7. Sample Bottle Solvent Rinse (First Aliquot)
Add 10 mL of methylene chloride to the sample bottle. Rinse the bottle thoroughly and set aside momentarily.
8. Pre-Elution Disk Wetting
Wet the disk with a small amount of acetone — just enough to wet the surface (approximately 0.5 mL or less). Immediately transfer the methylene chloride from the sample bottle to the disk with a disposable pipette, rinsing the sides of the filtration reservoir in the process.
9. First Elution Pull
Pull half of the solvent through the disk, then release the vacuum. Allow the remaining methylene chloride to soak the disk for about one minute, then draw the remainder through under vacuum.
10. Second Solvent Rinse & Direct Elution
Repeat the solvent rinse of the sample bottle using 5 mL methylene chloride and transfer to the apparatus, rinsing down the sides of the reservoir. Add another 5 mL methylene chloride directly on the disk, let soak for about one minute, and draw through under vacuum.
11. Eluate Drying
Dry the combined eluate with anhydrous sodium sulfate. Rinse the collection tube and sodium sulfate with two 5 mL aliquots of methylene chloride and place the combined solvent into a concentrator tube.
12. Concentration to 1.0 mL
Concentrate the extract to 1.0 mL under a gentle stream of nitrogen (may be warmed gently at approximately 30 °C).
⚠ Critical concentration note: The 30 °C nitrogen concentration is intentionally mild to minimize evaporative loss of the lighter-MW PAHs (especially Naphthalene). Even with this controlled approach, Naphthalene recoveries are inherently lower than higher-MW PAHs due to its higher vapor pressure — a well-documented limitation across all PAH analytical methods using nitrogen evaporation, not specific to SPE disk extraction.
13. GC-FID Analysis
Analyze the concentrated extract by GC-FID per the EPA QTM method conditions. If interfering compounds are detected, apply the cleanup protocols described in the EPA QTM method before re-analysis.
Recovery Validation Results
Recovery validation was performed on real-world groundwater samples from hazardous waste sites at two spike levels:
High Level (200 ppb): Compounds spiked at 200 ppb into groundwaters from two different hazardous waste sites, n = 6 replicates
Low Level (20 ppb): Compounds spiked at 20 ppb into groundwater from a hazardous waste site, n = 3 replicates
Table 1 — PAH Recovery in Groundwater at Two Spike Levels
Validation outcome:
Average RSD: 5.9% at the 200 ppb spike level (n=6)
Average RSD: 6.2% at the 20 ppb spike level (n=3)
All 7 EPA priority carcinogenic PAHs > 87% at 20 ppb level
Naphthalene recovery (47–48%) reflects volatility loss during nitrogen concentration — a well-known method limitation, not specific to SPE disk extraction
Conclusion
A simple and effective method for the extraction of PAHs from large-volume water samples (100 mL) using the CDS Empore™ 47 mm C18 SPE disk has been validated per the U.S. EPA Quick Turnaround Method (QTM). 16 PAHs extracted from groundwater samples were quantified by GC-FID at two spike levels:
200 ppb spike level (high) — average RSD 5.9% across 16 PAHs (n = 6)
20 ppb spike level (low) — average RSD 6.2% across 16 PAHs (n = 3)
All 7 EPA priority carcinogenic PAHs achieved > 87% recovery at the 20 ppb level
The Empore™ 47 mm C18 disk demonstrates clear advantages over traditional packed-bed SPE cartridges for large-volume aqueous PAH analysis: faster sample throughput, uniform retention, lower solvent consumption, and a workflow well-aligned with the "Quick Turnaround" priorities of the EPA QTM method. This method can be used as a screening tool for environmental testing labs analyzing PAH concentrations in aqueous samples.
Frequently Asked Questions
What are the 7 PAHs classified as carcinogenic by the US EPA?
Seven polycyclic aromatic hydrocarbons have been classified by the U.S. Environmental Protection Agency as potentially carcinogenic, mutagenic, and teratogenic:
Benz[a]anthracene
Benzo[a]pyrene
Benzo[b]fluoranthene
Benzo[k]fluoranthene
Chrysene
Dibenz[a,h]anthracene
Indeno[1,2,3-cd]pyrene
These seven priority PAHs are the primary regulatory targets for drinking water and environmental water monitoring programs.
What is the EPA Quick Turnaround Method (QTM)?
The U.S. EPA Quick Turnaround Method (QTM) is a streamlined SPE-based procedure for the rapid analysis of polycyclic aromatic hydrocarbons in aqueous samples. It uses a 47 mm C18 SPE disk to extract PAHs from a 100 mL water sample, followed by methylene chloride elution, anhydrous sodium sulfate drying, nitrogen concentration to 1.0 mL, and GC-FID quantitation. The QTM is designed for screening environmental and drinking water samples where fast turnaround is more important than the more comprehensive (and slower) EPA Method 525.2 GC-MS workflow.
What recoveries does the Empore C18 disk achieve for PAHs in water?
Validation in groundwater from hazardous waste sites achieved the following PAH recoveries with the Empore 47 mm C18 SPE disk:
At the 200 ppb spike level (n=6): recoveries ranged from 47.0% (Naphthalene) to 74.4% (Benzo[g,h,i]perylene) with an average RSD of 5.9%
At the 20 ppb spike level (n=3): recoveries ranged from 48.2% (Naphthalene) to 94.0% (Indeno[1,2,3,c,d]pyrene) with an average RSD of 6.2%
Recoveries for the 7 EPA priority carcinogenic PAHs were consistently above 67% at the 200 ppb level and above 87% at the 20 ppb level
Why is naphthalene recovery lower than other PAHs?
Naphthalene is the lowest molecular weight PAH (MW 128) with the highest vapor pressure and lowest boiling point of all monitored PAHs. During the nitrogen concentration step (eluate concentrated from approximately 25 mL down to 1.0 mL at ~30°C), naphthalene is partially lost to evaporation along with the methylene chloride solvent. This is a well-known limitation across all PAH analytical methods using nitrogen evaporation concentration, not specific to SPE disk extraction. The 47–48% naphthalene recovery observed here is consistent with results reported across the analytical literature for similar workflows.
Why is a 47 mm C18 disk used instead of a traditional SPE cartridge?
The Empore 47 mm C18 SPE disk demonstrates significant advantages over traditional packed-bed SPE cartridges for large-volume aqueous PAH analysis. The disk format eliminates channeling effects, processes the 100 mL sample volume faster than cartridge SPE, and produces uniform analyte retention across samples. The thin disk geometry also requires less elution solvent (methylene chloride) than typical packed-bed cartridges, reducing solvent consumption and concentration time. These advantages make the disk format particularly suited to the EPA Quick Turnaround Method for environmental screening laboratories.
What sample volume does this method use?
This EPA QTM method uses a 100 mL aqueous sample volume per Empore 47 mm C18 disk. This is smaller than the 1 L volumes specified in EPA Method 525.2 for the same compound class, reflecting the QTM's design priority of fast turnaround time over the lowest possible detection limits. For drinking water and environmental screening at the 20–200 ppb range, the 100 mL volume provides sufficient sensitivity while substantially reducing extraction time.
What is the role of bromofluorene in this method?
Bromofluorene is added as a surrogate compound to monitor extraction performance for each individual sample. Surrogates are non-analyte compounds with similar chemistry to the target PAHs that are spiked into every sample at a known concentration before extraction. The surrogate recovery in each sample provides an internal control on whether SPE extraction, elution, and concentration steps were performed correctly. In this validation, bromofluorene recovered at 73.1% (200 ppb level, RSD 5.9%) and 58.4% (20 ppb level, RSD 14.4%).
What detector is used for PAH quantitation in this method?
Detection is performed by GC-FID (Gas Chromatography with Flame Ionization Detection) per the EPA Quick Turnaround Method. While GC-MS provides additional structural confirmation and is required by EPA Method 525.2, the GC-FID detector used in QTM offers fast turnaround, low operating cost, and sufficient sensitivity for PAH screening in environmental and drinking water samples. If interfering compounds are detected in real-world samples, the EPA QTM specifies cleanup protocols that can be applied prior to GC-FID analysis.
References
U.S. Environmental Protection Agency. Quick Turnaround Method (QTM) for the Analysis of Polynuclear Aromatic Hydrocarbons in Water by SPE and GC-FID. U.S. EPA.
Lu G. CDS Analytical Application Note #206: Analysis of Polynuclear Aromatic Hydrocarbons Using US EPA Quick Turnaround Method (QTM) by CDS Empore™ Disk. CDS Analytical, LLC.
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