Investigating the extraction efficiency of dioxins in several types of aqueous matrices by automated SPE utilizing disks

Application note scope

The purpose of this application note is to outline an automated extraction method utilizing the Atlantic® DVB SPE Disk and the Biotage automated and manual SPE solutions for the extraction of dioxins and furans in several water matrices. 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® Horizon 4790 (with data and discussion) and Biotage® VacMaster^TM Disk for this application.

Introduction

Dioxins are of great environmental concern due to their teratogenic, mutagenetic, and carcinogenic impact. These lipophilic compounds bioaccumulate in humans and wildlife and can have half-lives of up to 132 years. They are known to bind to sediment or suspended particles.

Extraction using a solid phase extraction (SPE) disk is advantageous for extraction sediment laden samples because traditional SPE using a cartridge requires two extraction processes; a filtration step to remove particulates before extraction of the water sample is required due to the small cross sectional area of the cartridge leading to clogging, then the filtered particulates endure a separate extraction step, such as Soxhlet extraction. Not only that, if liquid-liquid extraction (LLE) is used, this can lead to formation of emulsions which can be difficult to break and may adversely affect the proper extraction of the particulate matter. The SPE disk extraction approach filters the particulates from the water sample on top of the disk while efficiently capturing the compounds of interest within the disk media. Prefilters are available but are not always required to filter the particulates from samples. The elution solvents delivered will effectively extract the dioxins and furans from the disk media while also extracting the compounds from the sediment on top of the disk.

Materials

• Biotage® Horizon® 5000
• 47 mm Atlantic® DVB Disks and pre-filters
• Sodium sulphate; combination clean-up cartridge containing silica gel, alumina, and florisil
• Genevac; miVac Evaporator (or equivalent)
• High Resolution Gas Chromatography (HRGC)/ High Resolution Mass Spectroscopy (HRMS)
  
  

Method summary

1. Clean all glassware and the extraction system using organic solvents and mild detergent to ensure the extractor’s liquid flow path is free of contaminants between samples.
2. Prepare samples as per Table 1: spike each sample with
   25 µL of a 20 pg/µL solution containing CDDs and CDFs and a 40 pg/µL for OCDD and OCDF and adjust the pH to 2.
   
   1. The samples represent a variety of matrices, including distilled water, very fine particulate laden river samples, river samples containing fine particles and sediment, and finally two wastewater influent samples.
   2. If larger sample volumes are required, the fast flow sediment disk holder with additional prefilters can be used, but since the disk holder is larger, solvent volumes and drain times would need to be increased accordingly to ensure recovery.
3. Let sit for 3 hours to equilibrate.
4. Extract samples with the automated Biotage® Horizon® 5000 extractor using Atlantic® DVB disks (47 mm), and pre-filters via the extraction method described in table 2.
5. Dry samples using sodium sulfate and then clean up using a coupling cartridge, containing silica gel, alumina and florisil. Concentrate samples on a miVac Evaporator (Genevac).
6. Analyze by high resolution gas chromatography (HRGC)/ high resolution mass spectroscopy (HRMS) following the conditions outlined in table 3.
   
   

Acknowledgements

Biotage LLC gratefully acknowledges the Carso Group France.

References

• EPA Method 1613, Tetra- through Octa-Chlorinated Dioxins and Furans by Isotope Dilution HRGC/HRMS, Revision B, October 1994.
• ISO Method 18073:2004 Determination of Tetra- through Octa-Chlorinated Dioxins and Furans by Isotope Dilution HRGC/ HRMS, reviewed and confirmed in 2013.

Application modifications

Biotage® Horizon 4790 method summary

1. Clean all glassware and the extraction system using organic solvents and mild detergent to ensure the extractor’s liquid flow path is free of contaminants between samples.
2. Prepare samples as per Table 1: spike each sample with 25 µL of a 20 pg/µL solution containing CDDs and CDFs and a 40 pg/µL for OCDD and OCDF and adjust the pH to 2.
   1. The samples represent a variety of matrices, including distilled water, very fine particulate laden river samples, river samples containing fine particles and sediment, and finally two wastewater influent samples.
   2. If larger sample volumes are required, the fast flow sediment disk holder with additional prefilters can be used, but since the disk holder is larger, solvent volumes and drain times would need to be increased accordingly to ensure recovery.
3. Let sit for 3 hours to equilibrate.
4. Extract samples with the automated Biotage® Horizon® 4790 extractor using Atlantic® DVB disks (47 mm), and pre-filters via the extraction method described in table 4.
5. Dry samples using sodium sulfate and then clean up using a coupling cartridge, containing silica gel, alumina and florisil. Concentrate samples on a miVac Evaporator (Genevac).
6. Analyze by high resolution gas chromatography (HRGC)/ high resolution mass spectroscopy (HRMS) following the conditions outlined in table 3.

Results and discussion

The tables below outline the results from each sample. Several different types of water samples were examined to see if significant differences in recovery were observed. Samples with suspended particles yielded higher recoveries (Table 6) than the LCS (Table 5) by a small amount. Table 7 shows results for samples with both particulate and sediment, providing an increasingly challenging matrix. The suspended particles and sediment in the bottle did lower the recoveries due to the compounds natural tendency to adhere to soil particles.

Wastewater influent samples, also a challenging matrix, were analysed and the results shown in (Table 8). Even in this matrix most of the compounds showed a reasonable recovery and good precision.

The use of an automated extraction system equipped with SPE disk technology yielded acceptable recoveries with particulate- laden water samples without the means of another extraction apparatus such as SDS (Soxhlet/Dean-Stark extractor).
Automated SPE extractions provide a fast method of extracting tetra through octa- chlorinated dioxins and furans from water matrices with analytical sensitivities to ppt (ng/L) levels.

Conclusion

Future work on these compounds will involve the extraction of larger volumes of samples (1 L or greater) using the EZ Flow Disk Holder. These studies will enable the analysis of samples with heavy particulate matter to be processed in a timely and efficient manor while lowering detection limits to the range of ppq (pg/L).

Biotage® VacMaster™ Disk Method Summary

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 (47mm): ensure the support screen is flat in the center 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 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:
   a. Guide for each conditioning step in Table 9 below:
   i. Measure the appropriate VOLUME of SOVENT into a graduated cylinder and pour into the disk holder assembly.
   ii. 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).
   iii. SATURATE the disk for the time shown (IN SECONDS). (Saturate means: quickly turn the knob to the appro- priate waste destination and back to the “OFF” position. This brings the solvent into the disk media bed).
   iv. SOAK the disk for the the time shown (IN SECONDS).
   v. DRAIN to the appropriate waste destination for the time shown (IN SECONDS). Switch to the “OFF” position.
6. Load the Sample:
   
   a. For multifunnel: quickly and efficiently angle the bottle to rest on the multifunnel upside-down.
   b. For no multifunnel: pour a portion of the sample into the disk holder.
   c. 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:
   
   a. Return the vacuum to -24”Hg and continue to air dry the SPE disk to “AQUEOUS” waste for an additional 600 SECONDS. Switch to the “OFF” position.
   b. Remove the sample bottle from the multifunnel if it was used.
   
   

Literature number: AN112