Extracting organochlorine pesticides & PCBs from water following EPA methods 8081 and 8082

Application note scope

This application note will outline optimized methods for the extraction of pesticides and PCBs as outlined in EPA methods 8081 & 8082 using Biotage automated or manual SPE solutions. The first section will highlight the use of the Biotage® Horizon 5000 fully automated extraction system and the method used for this application. Additionally, there will be an Application Modification section that will highlight the use of the Biotage® VacMaster™ Disk for this application.

Introduction

Traditional extraction methods for pesticides and PCBs 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 labour intensive, use large amounts of solvent, have matrix interfering emulsions, and require contaminant free glassware to determine trace amounts of these compounds 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 millilitres of solvents. Using solid phase extraction (SPE) allows us to use acetone and hexane as the extraction solvents for the determination of organochlorine pesticides in aqueous samples. Relative to the DCM-acetone 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 is accomplished by utilizing an SPE method based on the Biotage® Horizon 5000 Automated Extraction System in conjunction with a 47 mm Atlantic® HLB-M, DVB, or C18 extraction disk.

Pesticide and PCB pollution is a subject of global concern, and although many countries have now banned the use of these substances, they linger in the environment and can contaminate water sources. PCBs are extremely stable compounds, allowing them to bioaccumulated throughout the food chain and pesticides are toxic to animals and humans. These factors mean that methods which accurately and easily quantify them are essential to public health.

Instrumentation

»    Biotage® Horizon 5000 Automated Extraction System
»    Atlantic® HLB-M, DVB, or C18 SPE Disk (47mm)
»    Atlantic® Prefilter
»    Fast Flow Sediment Disk Holder (If extracting samples w/ particulates)
»    DryVap™* Concentrator System
»    DryDisk® Solvent Drying System

*The DryVap™ system has been discontinued. We recommend using the TurboVap® evaporation systems for achieving equivalent results.

Method summary

Extraction of particulate free aqueous samples (using standard 47 mm Disk holder)

1. Adjust a 1 L aqueous sample to a pH of 2 with HCL. Cap the bottle and mix.
2. Spike any laboratory control or matrix spike samples with the appropriate spike mix. (If only analysing 8081, use only pesticide spike. Likewise, for 8082 use only PCB spike)
3.  Spike all samples with the appropriate amount of surrogate.
4.  Place the sample bottle on the Biotage® Horizon 5000 Extraction System and place the Atlantic® HLB-M, DVB, or C18 disk in the standard 47mm disk holder.
5. Run the Biotage® Horizon 5000 using the extraction method detailed in table 2, using acetone and hexane as the extraction solvents.
6. After the extraction is complete collect the extract.
7. Dry and concentrate the extract to a final volume of 5.0 mL. (If using DryVap™ , utilize parameters in table 1)
8.  Perform any necessary clean-ups of sample extract such as Florisil, sulfuric acid, and mercuric precipitation.
9. Analyze by GC/ECD.

Extraction of aqueous samples with particulates (using the 47 mm Fast Flow Sediment Disk Holder (FFSDH))

1. Adjust a 1 L aqueous sample to a pH of 2 with HCL. Cap the bottle and mix.
2. Spike any laboratory control or matrix spike samples with the appropriate spike mix. (If only analysing 8081, use only pesticide spike. Likewise, for 8082 use only PCB spike)
3. Spike all samples with the appropriate amount of surrogate.
4. Place the sample bottle on the Biotage® Horizon 5000 Extraction System and place the Atlantic® HLB-M, DVB, or C18 disk in the fast flow disk holder with an Atlantic® Prefilter on top of the support screen.
5. Run the Biotage® Horizon 5000 using the extraction method detailed in table 3 using acetone and hexane as the extraction solvents.
6. After the extraction is complete collect the extract.
7. Dry and concentrate the extract to a final volume of 5.0 mL. (If using DryVap™ , utilize parameters in table below)
8.  Perform any necessary clean-ups of sample extract such as Florisil, sulfuric acid, and mercuric precipitation.
9.  Analyze by GC/ECD.
   
   

Acknowledgements

Our thanks go to Sharlene Robinson from GEL Laboratories and Ann Casey from Northeast Analytical Inc. for their assistance in developing these methods.

Application modifications

Biotage® VacMaster™ Disk method summary (using a Standard 47mm Disk Holder with 47 mm Disk)

1. Repeat the following steps for each active Biotage® VacMaster™ Disk station.
2. Setup the VacMaster™ Disk manifolds ensuring all waste lines and vacuum lines are attached. Set the vacuum pump to -24”Hg.
3. Prepare the disk holder assembly (47 mm): ensure the support screen is flat in the centre of the disk holder. Place the Atlantic® DVB Disk on top of the support screen with the ripples of the disk on top and add any prefilters on top of the disk. Place the disk holder assembly on the VacMaster Disk manifold ensuring there is a tight seal with the luer fitting.
4. If using the multifunnel, place onto the disk holder assembly. If not using the multifunnel, omit those directions throughout the method.
5. Condition the SPE Disk:
   Guide for each conditioning step in table below:
   
   1. Measure the appropriate VOLUME of SOLVENT into a graduated cylinder and pour into the disk holder assembly.
   2. Using a Nalgene Wash Bottle (phthalate free), rinse the multifunnel and disk holder in a circle for about 3 seconds using the same SOLVENT (approximately 5 additional mL).
   3. SATURATE the disk for the time indicated (in SECONDS). (Saturate means: quickly turn the knob to the appropriate waste destination and back to the “OFF” position. This brings the solvent into the disk media bed).
   4. SOAK the disk for the time indicated (in SECONDS).
   5. DRAIN to the appropriate waste destination for the time indicated (in SECONDS). Switch to the “OFF” position.
      

      Solvent	Volume (mL)	Saturate (sec)	Soak (sec)	Waste Destination	Drain (sec)
      Hexane	15	1	60	Organic	20
      Acetone	11	1	60	Organic	20
      Reagent Water	15	1	60	Aqueous	2

6. Load the sample:
   1. For multifunnel: quickly and efficiently angle the bottle to rest on the multifunnel upside-down.
   2. For no multifunnel: pour a portion of the sample into the disk holder.
   3. Adjust the vacuum between -10”Hg and -15”Hg for sample load (please note, if the sample is flowing too slowly, the vacuum can be increased). Drain the sample to “AQUEOUS” waste. Continue to pour the sample into the disk holder ensuring the disk does not go dry or overflow for the duration of sample load.
7. Air Dry the SPE Disk:
   1. Return the vacuum to -24”Hg and continue to air dry the SPE disk to “AQUEOUS” waste for an additional 60 SECONDS. Switch to the “OFF” position.
   2. Remove the sample bottle from the multifunnel if it was used.
      
      
8. Elute the SPE Disk: (Please note: the elution solvent will go into the collection flask inside the chamber, not to waste containers)
   1. Place a clean 125 mL 24/40 tapered Erlenmeyer flask into the VacMaster™ Disk collection chamber. Place the cover on the chamber. Remove the disk holder assembly and place the disk holder assembly into the luer fitting on top of the collection chamber. Attach the luer fitting of the collection chamber assembly onto the manifold.
   2. Guide for each elution step in table 5 below:
   3. Measure the appropriate VOLUME of SOLVENT into a graduated cylinder, pour into the sample bottle, and swirl around. Pour the solvent in the sample bottle into the disk holder assembly.
   4. Using a Nalgene Wash Bottle (phthalate free), rinse the multifunnel and disk holder in a circle for about 3 seconds using the same SOLVENT (approximately 5 additional mL).
   5. SATURATE the disk for the time indicated (in SECONDS) to “ORGANIC”.
   6. SOAK the disk for the time indicated (in SECONDS).
   7. DRAIN to “ORGANIC” for the time indicated (in SECONDS). Switch to the “OFF” position.
   8. Remove the chamber lid to release the vacuum from inside the chamber.
      
      

Biotage® VacMaster™ Disk method summary (using a Fast Flow Sediment Disk Holder with 47 mm Disk)

1. Repeat the following steps for each active VacMaster™ Disk station.
2. Setup the VacMaster™ Disk manifolds ensuring all waste lines and vacuum lines are attached. Set the vacuum pump to -24”Hg.
3. Prepare the disk holder assembly (FFSDH): place the Atlantic® DVB Disk into the narrow part on the bottom of the FFSDH disk holder so the ripples of the disk are on the top, then place the riser with the SPE disk support screen under the disk and attach the 47mm ring cap to create a seal. On the wider portion of the disk holder, place the support screen (ensuring it is flat and in the centre of the disk holder) and add any prefilters on top of the screen. Place the disk holder assembly onto the VacMaster™ Disk manifolds ensuring there is a tight seal with the luer fitting.
4. If using the multifunnel, place onto the disk holder assembly. If not using the multifunnel, omit those directions throughout the method.
5. Condition the SPE Disk
   Guide for each conditioning step in table 6 below:
   
   
   1. Measure the appropriate VOLUME of SOLVENT into a graduated cylinder and pour into the disk holder assembly.
   2. Using a Nalgene Wash Bottle (phthalate free), rinse the multifunnel and disk holder in a circle for about 3 seconds using the same SOLVENT (approximately 5 additional mL).
   3. SATURATE the disk for the time indicated (in SECONDS). (Saturate means: quickly turn the knob to the appropriate waste destination and back to the “OFF” position. This brings the solvent into the disk media bed).
   4. SOAK the disk for the time indicated (in SECONDS).
   5. DRAIN to the appropriate waste destination for the time indicated (in SECONDS). Switch to the “OFF” position.
      

      Solvent	Volume (mL)	Saturate (sec)	Soak (sec)	Waste Destination	Drain (sec)
      Hexane	20	1	60	Organic	45
      Acetone	20	1	60	Organic	45
      Reagent Water	18	1	60	Organic	4

6. Load the sample:
   1. For multifunnel: quickly and efficiently angle the bottle to rest on the multifunnel upside-down.
   2. For no multifunnel: pour a portion of the sample into the disk holder.
   3. Adjust the vacuum between -10”Hg and -15”Hg for sample (please note, if the sample is flowing too slowly, the vacuum can be adjusted increased).
      Drain the sample to “AQUEOUS” waste. Continue to pour the sample into the disk holder ensuring the disk does not go dry or overflow for the duration of sample load.
7. Air Dry the SPE Disk:
   1. Return the vacuum to -24”Hg and continue to air dry the SPE disk to “AQUEOUS” waste for an additional 60 SECONDS. Switch to the “OFF” position.
   2. Remove the sample bottle from the multifunnel if it was used.
      
      
8. Elute the SPE Disk: (Please note: the elution solvent will go into the collection flask inside the chamber, not to waste containers)
   1. Place a clean 125mL 24/40 tapered Erlenmeyer flask into the VacMaster™ Disk collection chamber. Place the cover on the chamber. Remove the disk holder assembly and place the disk holder assembly into the lure fitting on top of the collection chamber. Attach the lure fitting of the collection chamber assembly onto the manifold.
   2. Guide for each elution step in table 7 below:
      
      
      1. IMeasure the appropriate VOLUME of SOLVENT into a graduated cylinder, pour into the sample bottle, and swirl around. Pour the solvent in the sample bottle into the disk holder assembly.
      2. Using a Nalgene Wash Bottle (phthalate free), rinse the multifunnel and disk holder in a circle for about 3 seconds using the same SOLVENT (approximately 5 additional mL).
      3. SATURATE the disk for the time indicated (in SECONDS) to “ORGANIC”.
      4.  SOAK the disk for the time indicated (in SECONDS).
      5. DRAIN to “ORGANIC” for the time indicated (in SECONDS). Switch to the “OFF” position.
      6.  Remove the chamber lid to release the vacuum from inside the chamber.
         
         

Literature number: AN067-HOR