Determination of PAHs from sea water using automated SPE

Scope

This application note will outline optimized methods for the extraction of polycyclic aromatic hydrocarbons from sea water using Atlantic® HLB solid phase extraction disk processed using Biotage automated or manual SPE solutions and DryVap™* concentrator system. 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.

*The DryVap™ system has been discntinued.

Introduction

Polycyclic aromatic hydrocarbons (PAHs) are an important class of environmental contaminants because of their prevalence and potentially adverse health effects. PAHs are generated in exhaust from gasoline and diesel engines, and emissions from the combustion of most organic compounds.

When people are exposed to some PAHs at levels above the maximum concentration limit for relatively short periods of time red blood cell damage, leading to anaemia, and a suppressed immune system can occur. Long-term exposure is believed to potentially have negative developmental and reproductive side-effects and cause some forms of cancer.

PAHs released into coastal seawaters have been proven to be a prevalent problem and are thought to be responsible for some of the biological effects on marine life such as chromosomal problems in fish and other marine organisms. Sources of this include natural seepage, platforms, pipelines, produced waters, vessel spills, vessel operations, aircraft dumping, and coastal facilities.

The Biotage® Horizon 5000 automated extraction system provides for the automated extraction of liquid samples via SPE methods. The system can handle sample volumes ranging from 20 mL to 4 L, and matrices such as wastewater and sea water. The instrument software provides a user-friendly operation system, capable of interacting with up to 4 extractors via a standard PC connection. The DryVap™ concentrator system provides automated sample drying, with a patented PTFE membrane technology that automatically

Instrumentation

• Biotage Instruments
  »  Biotage® Horizon 5000 Automated Extraction System
  » DryVap™ Concentrator System
  » DryDisk® Separation Membrane
  » Biotage® Solvent Recovery SVOC System
  » Atlantic® HLB Disk (47mm)
• Agilent 6890 GC w/ 5973 Mass Selective Detector
• Cartridge: DB 5MS 30 m x 0.25 mm ID, 0.25 um
  
  

Method Summary

1. Obtain 1 L samples, preserve with 1.0 mL of concentrated HCl (pH = 2) and refrigerate.
2. Spike any control samples with 50 µg of the PAHs of interest.
3. Place sample bottles on the Biotage® Horizon 5000 system and place Atlantic® HLB SPE disks in the disk holders.
4. Place 40 mL VOA vials or equivalent onto the extraction systems for extract collection.
5. Start the method in table 1 and collect the final extract upon completion.
6. Pour the final sample extract into the DryDisk® reservoir.
7. Dry the sample and concentrate to 0.9 mL using the DryVap™ with the settings in table 2.
8. Rinse the bottom of the concentrator tube with methylene chloride to bring the extract up to a final volume of 1 mL.
9. Transfer 0.4 mL of extract to a GC vial and add 8 µL of Internal Standard solution.
10. Analyze sample extracts via GC/MS.

Application modifications

Biotage® VacMaster™ Disk method summary

1. Repeat the following steps for each active Biotage® VacMaster™ Disk station.
2. Set up 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 (47mm): ensure the support screen is flat in the centre of the disk holder. Place the Atlantic® HLB-M 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:
   1. Guide for each conditioning step in table 3 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.
         
         

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 4 below:
   1. 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.
   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: AN038