Removing Semi-Volatile Organic Compounds (SVOCs) from Soil

Semi-volatile organic compounds (SVOCs) are commonly found in abundance in soil. Yet, extracting these compounds from soil can be a long and arduous process. The EDGE® is a pioneering and simple system for numerous kinds of extractions, including the rapid extraction of SVOCs from soil.

Removing Semi-Volatile Organic Compounds (SVOCs) from Soil

Image Credit: CEM Corporation 

The Q-Cup® technology brings together the processes of pressurized fluid extraction (PFE) and dispersive solid phase extraction (dSPE) while also offering an easy setup.

With its unique open cell concept, the Q-Cup generates a dispersive effect and encourages rapid extraction and filtration. The EDGE provides a quick and easy extraction which is also efficient while complying with EPA 3045A.

Introduction

Semi-volatile organic compounds (SVOCs) are a subgroup of volatile organic compounds (VOCs) that possess high molecular weights and greater boiling points than VOCs. These compounds include polyaromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), phthalates and plasticizers.

Several of these compounds have been prohibited for use due to both their toxicity and persistence in the environment. Being exposed to these compounds for prolonged periods of time, especially indoors, has brought up public health concerns, prompting their categorization by the US EPA as hazardous air pollutants (HAPs).

Compounds categorized under this grouping can cause severe health effects, such as asthma, allergies, endocrine and thyroid disruption, fetal and child development delays, reproductive toxicity and even cancer.

SVOCs are comprised of compounds with a diverse range of structural features and chemical properties. These differences make it difficult to extract all analytes of interest efficiently with a single method.

Additionally, the complexity of the extraction is complicated by the soil matrix from which the SVOCs are to be extracted, as it often includes numerous components.

The EDGE, an automated solvent extraction system, has the capacity to manage these issues and successfully extract a complex set of analytes from intricate matrices with a simple, singular method.

Conventional methods, such as Soxhlet, are laborious and time-sapping and require a large amount of solvent. Other automated methods often necessitate monotonous sample preparation and the setup of complex sample holders.

In contrast, the EDGE offers a modern automated method that takes less time and uses less solvent. The EDGE sample holder, the Q-Cup, is also simple to assemble as it is made up of only two components, meaning the sample can be prepared in seconds.

Due to their persistent nature, SVOCs amass and concentrate in our environment. These compounds need to be extracted accurately and efficiently, following governmental regulations like EPA 3545A, to guarantee health and safety.

The EDGE is compliant with EPA 3545A for the extraction of water-insoluble or slightly water-soluble volatile and semi-volatile compounds in clays, sediments, sludges, soils and waste solids. The EDGE streamlines the process, producing an extract that is cooled, filtered and ready for analysis in less than 20 minutes.

Materials and Method

Reagents

Clean clay, sodium sulfate and Florisil were acquired from Sigma Aldrich. A CEM Phoenix Microwave Muffle Furnace was used to bake the sodium sulfate at 400 °C. Sigma Aldrich also provided BNAs in Soil CRM, and the deactivated glass wool was purchased from Restek.

An SVOC standard (Cat No 31850) made up of 76 compounds, and a semi-volatile internal standard mix (Cat No 31206) was also acquired via Restek. Fisher Scientific supplied ACS grade acetone and ACS grade hexane.

Sample Preparation

For the BNAs in Soil CRM, a Q-Cup was set up with an S1 Q-Disc stack. Firstly, 20 grams of sample was weighed into a Q-Cup, and then 30 g of sodium sulfate was added on top. Subsequently, the mixing of the sample was performed using a clean metal spatula.

After the sample was mixed thoroughly, the spatula was cleaned with a Kimwipe, and the Kimwipe was placed into the Q-Cup.

Two grams of Florisil was weighed and placed on top of each sample, making sure that the whole of the sample was covered. A Q-Screen was then placed into the Q-Cup opening, ensuring that the layer of Florisil remained undisturbed.

The samples were prepared in quadruplet. The EDGE was used for the extraction of each sample which was then collected in a 60 mL glass collection vial.

Additionally, for the wet clay samples, a Q-Cup was also assembled with an S1 Q-Disc stack. Twenty grams of the clay sample mixed with 30 g of sodium sulfate was weighed into a secondary container.

Half of the mixture was then placed into the Q-Cup. Using an automated pipette, the sample was spiked with 200 µL of 100 µg/mL semi volatile organic compound spiking standard for a final concentration of 20 µg.

The remainder of the sample was then weighed on top. Two grams of Florisil was weighed on top of each sample, ensuring that the whole top of the sample was covered. A Q-Screen was then placed into the Q-Cup opening, ensuring that the layer of Florisil was not disturbed. Each sample was prepared in triplet.

The EDGE was used for the extraction of each sample which was then collected in a 60 mL glass collection vial.

EDGE Method for SVOCs from Soil

Q-Disc: S1 Q-Disc Stack (C9+G1+C9 sandwich)

Cycle 1:

  • Extraction Solvent: Hexane/Acetone (1:1)
  • Top Add: 15 mL
  • Bottom Add: 0 mL
  • Rinse: 0 mL
  • Temperature: 70 ºC
  • Hold Time: 00:30 (mm:ss)

Cycle 2:

  • Extraction Solvent: Hexane/Acetone (1:1)
  • Top Add: 15 mL
  • Bottom Add: 0 mL
  • Rinse: 0 mL
  • Temperature: 70 ºC
  • Hold Time: 00:30 (mm:ss)

Cycle 3:

  • Extraction Solvent: Hexane/Acetone (1:1)
  • Top Add: 15 mL
  • Bottom Add: 0 mL
  • Rinse: 0 mL
  • Temperature: 100 °C
  • Hold Time: 00:30 (mm:ss)

Cycle 4:

  • Extraction Solvent: Hexane/Acetone (1:1)
  • Top Add: 15 mL
  • Bottom Add: 0 mL
  • Rinse: 0 mL
  • Temperature: 100 °C
  • Hold Time: 00:30 (mm:ss)

Wash 1:

  • Wash Solvent: Hexane/Acetone (1:1)
  • Wash Volume: 30 mL
  • Temperature: 125 ºC
  • Hold Time: 00:30 (mm:ss)

Wash 2:

  • Wash solvent: Hexane/acetone (1:1)
  • Wash volume: 30 mL
  • Temperature: - - -
  • Hold Time: - -:- - (mm:ss)

Analysis

Extracts were introduced to sodium sulfate as they were poured into glass funnels fixed in place by deactivated glass wool. Hexane was then used to rinse the sodium sulfate, and the extracts were evaporated under 1 mL in a Biotage Turbovap II.

Extracts were subsequently spiked with 20 µg of internal standard, brought up to volume with hexane, then relocated to a GC vial and injected on an Agilent 7890A GC with a 5975C MSD for analysis. A Phenomenex ZB-5MSplus 30 m, 0.25 mm column was utilized.

Results and Discussion

The EDGE extracted the SVOC compounds successfully from soil in less than 20 minutes, including cooling, filtration and system washing. The recovery data exhibited in Table 1 outlines how the extraction of the CRM sample was completed with excellent efficiency, with most recoveries in the 70% to 120% range.

Table 1. Average Recovery Results and RSD Values for CRM Soil Samples. Source: CEM Corporation

Compound Recovery RSD (n=4)
Phenol 67.78% 5.23%
Bis(2-chloroethyl)ether 87.94% 9.08%
2-Chlorophenol 80.11% 9.66%
2-Methylphenol 115.79% 5.86%
4-Methylphenol 139.09% 6.87%
n-Nitroso-di-n-propylamine 140.68% 9.21%
Nitrobenzene 99.37% 3.46%
Isophorone 83.08% 5.53%
2-Nitrophenol 80.29% 4.88%
2,4-Dimethylphenol 95.41% 1.64%
2,4-Dichlorophenol 96.74% 2.85%
1,2,4-Trichlorobenzene 84.87% 4.73%
Hexachlorobutadiene 88.80% 5.44%
2,4,6-Trichlorophenol 104.06% 3.61%
2,4,5-Trichlorophenol 104.92% 2.29%
2-Chloronaphthalene 91.49% 11.65%
Dimethyl phthalate 108.45% 2.26%
2,6-Dinitrotoluene 110.48% 2.28%
Acenaphthylene 93.11% 1.47%
Acenapthene 99.36% 3.08%
4-Nitrophenol 90.02% 9.38%
Dibenzofuran 100.46% 4.31%
Diethyl phthalate 103.77% 6.17%
Fluorene 97.82% 6.86%
4-Chlorophenyl-phenylether 103.00% 5.89%
4,6-Dinitro-2-methylphenol 54.74% 21.41%
Pentachlorophenol 89.19% 13.53%
Phenanthrene 112.42% 3.15%
Anthracene 118.92% 3.15%
Fluoranthene 110.02% 4.88%
Pyrene 106.42% 3.34%
Benzyl butyl phthalate 107.70% 6.04%
Benz[a]anthracene 106.07% 2.75%
Chrysene 104.31% 6.57%
Bis(2-ethylhexyl)phthalate 117.11% 5.64%
Di-n-octyl phthalate 99.39% 5.89%
Benzo[b]fluoranthene 92.60% 10.50%
Benzo[k]fluoranthene 116.85% 8.13%
Benzo[a]pyrene 100.02% 10.03%
Indol[1,2,3-cd]pyrene 115.71% 6.53%
Dibenz[a,h]anthracene 111.86% 5.66%
Benzo[g,h,i]perylene 112.56% 7.27%

 

The consequent RSD values were also low (all less than 15%), demonstrating that the recovery data was reproducible. The recovery data shown in Table 2 outlines a spiked wet clay soil. A significant majority of recoveries for the compounds was between 70% to 120%, and for most RSD, values were under 20%.

Table 2. Average Recovery Results and RSD Values for Spiked Wet Clay Soils. Source: CEM Corporation

Compound Recovery RSD (n=3)
n-Nitrosodimethylamine 86.92% 3.27%
Pyridine 90.56% 2.39%
Phenol 78.89% 5.85%
Aniline 87.43% 6.51%
Bis(2-chloroethyl)ether 72.80% 11.52%
2-Chlorophenol 74.40% 8.01%
1,3-Dichlorobenzene 53.10% 15.51%
1,4-Dichlorobenzene 37.01% 43.59%
Benzyl Alcohol 85.06% 6.09%
1,2-Dichlorobenzene 43.63% 48.42%
2-Methylphenol 65.61% 12.63%
2,2’-Oxybis(1-chloropropane) 70.83% 27.66%
4-Methylphenol 69.18% 8.83%
n-Nitroso-di-n-propylamine 80.92% 14.40%
Hexachloroethane 39.34% 34.66%
Nitrobenzene 71.46% 20.69%
Isophorone 86.51% 11.64%
2-Nitrophenol 76.19% 14.34%
2,4-Dimethylphenol 30.83% 11.54%
Bis(2-chloroethoxy)methane 75.37% 11.78%
2,4-Dichlorophenol 81.23% 10.65%
1,2,4-Trichlorobenzene 59.78% 21.02%
Naphthalene 74.44% 16.37%
4-Chloroaniline 77.49% 11.04%
Hexachlorobutadiene 69.46% 19.39%
4-Chloro-3-methylphenol 98.53% 8.09%
2-Methylnaphthalene 85.72% 11.80%
1-Methylnaphthalene 85.72% 11.80%
Hexachlorocyclopentadiene 84.79% 12.12%
2,4,6-Trichlorophenol 92.88% 8.14%
2,4,5-Trichlorophenol 101.43% 9.99%
2-Chloronaphthalene 86.57% 15.23%
2-Nitroaniline 96.57% 10.37%
1,4-Dinitrobenzene 94.41% 10.80%
Dimethyl phthalate 98.52% 9.44%
2,6-Dinitrotoluene 101.84% 7.47%
Acenaphthylene 76.74% 9.27%
1,2-Dinitrobenzene 97.03% 8.08%
3-Nitroaniline 94.03% 7.08%
Acenapthene 93.15% 8.31%
2,4-Dinitrophenol 105.27% 1.50%
4-Nitrophenol 100.28% 8.70%
Dibenzofuran 98.40% 8.69%
2,4-Dinitrotoluene 109.36% 5.02%
2,3,5,6-Tetrachlorophenol 101.88% 3.10%
2,3,4,6-Tetrachlorophenol 105.24% 6.31%
Diethyl phthalate 103.54% 4.84%
Fluorene 99.48% 7.88%
4-Chlorophenyl-phenylether 99.18% 7.93%
4-Nitroaniline 105.66% 6.14%
4,6-Dinitro-2-methylphenol 99.87% 4.32%
Diphenylamine 90.24% 3.81%
Azobenzene 100.66% 7.62%
1-Bromo-4-phenoxybenzene 101.63% 5.83%
Hexachlorobenzene 108.48% 6.97%
Pentachlorophenol 105.97% 4.14%
Phenanthrene 99.16% 3.40%
Anthracene 99.16% 3.40%
Carbazole 105.25% 1.13%
Dibutyl phthalate 106.25% 1.12%
Fluoranthene 103.34% 3.98%
Pyrene 103.34% 3.98%
Benzyl butyl phthalate 98.92% 3.71%
Benz[a]anthracene 103.65% 2.52%
Bis(2-ethylhexyl)phthalate 102.71% 1.39%
Di-n-octyl phthalate 107.11% 1.79%
Chrysene 106.95% 4.35%
Benzo[b]fluoranthene 120.60% 7.43%
Benzo[k]fluoranthene 106.14% 4.32%
Benzo[a]pyrene 108.06% 7.52%
Indol[1,2,3-cd]pyrene 108.34% 7.21%
Dibenz[a,h]anthracene 106.65% 2.25%
Benzo[g,h,i]perylene 102.16% 2.75%

 

Conclusion

Identifying the presence and extracting semi volatile organic compounds in solid matrices is vital when monitoring the environment and subsequently protecting human health.

The EDGE offers a simple, rapid and efficient extraction when compared to conventional methods. Recovery values for a range of compounds were within the appropriate ranges with low RSD values.

It is critical that the correct sample preparation, both mixing the sample with sodium sulfate for sample dispersion as well as utilizing Florisil to snare the more volatile compounds, is properly performed for the extraction.

This information has been sourced, reviewed and adapted from materials provided by CEM Corporation.

For more information on this source, please visit CEM Corporation.

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