Drinking water extraction using Atlantic® high-capacity SPE disks

Application note scope

The purpose of this application note is to outline an automated extraction method utilizing the Atlantic® C18-HC SPE Disk and the Biotage automated and manual SPE solutions for the extraction of organic compounds in drinking water. 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 Disk for this application.

Introduction

For more than 25 years now, the US has been testing for organic compounds in drinking water using US EPA Method 525.1 The most common version of this method, Method 525.2, is a diverse method with more than 100 compounds listed in a wide range of chemical groups such as pesticides, polychlorinated biphenyls, and polyaromatic hydrocarbons. Method 525.3 offers other changes to the method that may also be of use in making the method more rugged. Additional compounds are evaluated and may be added to the method as the regulatory list is amended every few years.

With increased experience, it has come to be known that certain compounds on the list are difficult to retain using the types of solid-phase extraction (SPE) disks that were available on the market, particularly the more polar compounds. This application note will highlight a new SPE disk which was specifically designed to increase the recoveries of these difficult compounds as well as help to increase the diversity of the traditional 525.2 list to include those compounds which are of concern in today’s society.

 
Instrumentation

Biotage instruments

» Biotage® Horizon 5000 Automated Extraction System

» Atlantic® C18-HC SPE Disk Agilent

» 6890 GC/MS

Method summary

1. Adjust 1 litre of sample to a pH less than two.
2. Spike surrogate and internal standard compounds into samples.
3. Spike analyte standards into samples.
4. Attach an appropriate collection vessel to the instrument.
5. Place a 47-mm Atlantic® C18-HC disk in the disk holder and assemble the disk holder.
6.  Place the disk holder on the extractor.
7. Load the sample container onto the Biotage® Horizon 5000.
8.  Start extraction method given in Table below using the following conditions:
9. The resulting extract volume should be approximately 20 mL.
10. Dry the extract using either a hydrophobic membrane such as the DryDisk®, DryDisk®-R, or sodium sulphate.
11. Concentrate the extract to a final volume of 1.0 mL.
12. Transfer a portion of the extract to a GC vial with insert.
13. Analyze by GC/MS.
    
    

References

1. Method 525.2: Determination of Organic Compounds in Drinking Water By Liquid-Solid Extraction and Capillary Cartridge Gas Chromatography/Mass Spectrometry, Revision 2.0, 1995, http://water.epa.gov/scitech/methods/cwa/ upload/Methods-for-the-Determination-of-Organic- Compounds-in-Drinking-Water.pdf
   
   

Method modifications

Biotage® Horizon 4790 method summary

1. Adjust 1 litre of sample to a pH less than two.
2. Spike surrogate and internal standard compounds into samples.
3. Spike analyte standards into samples.
4. Attach an appropriate collection vessel to the instrument.
5. Place a 47-mm Atlantic® C18-HC disk in the disk holder and assemble the disk holder.
6. Place the disk holder on the extractor.
7. Load the sample container onto the Biotage® Horizon 4790.
8.  Start extraction method given in Table below using the following conditions:
9. The resulting extract volume should be approximately 20 mL.
10. Dry the extract using either a hydrophobic membrane such as the DryDisk®, DryDisk®-R, or sodium sulphate.
11. Concentrate the extract to a final volume of 1.0 mL.
12. Transfer a portion of the extract to a GC vial with insert.
13. Analyze by GC/MS

Results and discussion

The data in Table 3 exhibits both excellent recoveries and relative standard deviations (RSDs) for most of the traditional 525.2 target analytes. The concentration of the analytes used in this study was selected to be approximately in the middle of the calibration range.

Of particular note, compounds such as 2,6-dinitrotoluene and 2,4-dinitrotoluene, which normally recover in the 50th to 60th percentile when using SPE disks with the standard loading capacity, were recovered in the 80th to 90th percentile when using this disk. The Atlantic® C18-HC disks, having double the capacity of most standard C18 SPE disks, were able to increase the recoveries by as much as a factor of 1.75 during independent laboratory testing.

Further, highly polar compounds such as caffeine are retained better using a higher capacity disk such as the Atlantic® C18-HC. In this case, caffeine was added to the standard mix because its presence in a water sample is directly related to human interac- tion. By testing for caffeine in water samples, the laboratory could track the impact that humans have on the surrounding water supplies.

Lastly, due to the increase in the disk capacity, it was necessary to monitor some compounds for a potential loss in recoveries. Any losses are due to the increased thickness of the disk and are easy to correct by adding an extra rinse step to fully elute all the target compounds from the SPE disk.

Conclusion

The Atlantic® C18-HC SPE disk is a simple and straightforward way to increase recoveries for SVOC compounds when testing in water. Its increased capacity allows for a more versatile disk, widening the range of compounds which can be extracted from aqueous samples.

Biotage® VacMaster™ Disk method summary

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 (47mm): ensure the support screen is flat in the centre of the disk holder. Place the Atlantic® C18-HC 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:
   1. a. Guide for each conditioning step in the 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 shown (in SECONDS). (Saturate means: quickly turn the knob to the proper waste destination and back to the “OFF” position. This brings the solvent into the disk media bed).
      4. SOAK the disk for the time shown (in SECONDS).
      5. DRAIN to proper waste destination for the time shown (in SECONDS). Switch to the “OFF” position.
         
         

         Solvent	Volume (mL)	Saturate (sec.)	Soak (sec.)	Waste Destination	Drain (sec.)
         Ethyl Acetate	11	1	60	Organic	60
         Methylene Chloride	15	1	60	Organic	60
         Methanol	11	1	60	Organic	5
         Reagent Water	15	1	5	Aqueous	5

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 120 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 elutions will go into the collection flask inside the chamber, not to waste containers)
   1. Place a clean 125 mL 24/40 tapered Erlenmeyer flask or 40 mL VOA vial (using the VOA vial insert) 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 the table below:
      
      
      1. Measure 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 shown (in SECONDS) to “ORGANIC”.
      4. SOAK the disk for the the time shown (in SECONDS).
      5. DRAIN to “ORGANIC” for the time shown (in SECONDS). Switch to the “OFF” position.
      6. Remove the chamber lid to release the vacuum from inside the chamber.

Literature number: AN101-HOR