Increasing Throughput and Recoveries for Highly Particulate and Sediment Laden Aqueous Samples Using the Fast Flow Sediment Disk Holder for Semi-Volatiles

Friday, May 13, 2011

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Please check out our Automated Solid Phase Extraction System (SPE System) section for more information or to find manufacturers that sell these products.

Introduction

Oftentimes, aqueous samples collected contain varying amounts of suspended solids or sediment strictly due to either the source of the water being sampled or improper sampling techniques. In any circumstance, samples with high amounts of particulates or sediment have proven challenging to extract using EPA Method 3535 Solid Phase Extraction (SPE).

The two options available for SPE are to either use a disk or a cartridge. Processing a high sediment sample with a SPE cartridge will result in instant clogging of the cartridge and failure to extract the “whole sample”. A standard 47 mm SPE disk provides many advantages over SPE cartridges. SPE disks can process a wide range of particulate laden samples, but the amount or size of the particulates may sometimes result in longer sample processing times. An alternative is to use a 100 mm SPE disk which has nearly four times the surface area of a 47 mm disk and will process a particulate laden sample at a faster flow rate. However, larger disk sizes require more sorbent and can be very expensive. It would be more costeffective to use an inexpensive 90 mm prefilter with a 47 mm SPE disk.

Horizon Technology’s Fast Flow Sediment Disk Holder combines the best of both worlds by allowing a sample to be processed using a 100 mm prefilter with a 47 mm SPE disk. The purpose of this study is to demonstrate the recoveries that can be achieved using this disk holder.

To demonstrate the effectiveness of the Fast Flow Sediment Disk Holder, a list of compounds from EPA Method 8270D was selected. This list contains a wide range of semivolatile compounds which required the use of both the Horizon Technology Dual pH Kit and the Carbon Cartridge Kit for the SPE-DEX 4790. These kits are typically already in use where EPA Method 8270D is being run on the SPE-DEX 4790.

The extractions were carried out with the use of the Atlantic HLB-H SPE disk which is able to retain a large list of organic semi-volatile compounds from EPA Method 8270D through its unique ratio of hydrophilic nvinylpyrrolidone and lipophilic divinylbenzene sorbent.

The Dual pH Kit in conjunction with the SPE-DEX 4790 allows for the recollection of an aqueous sample that would typically be discarded after the primary extraction has been completed. This means that the sample can then undergo a pH adjustment and be extracted once again, using the same SPE disk. Adding to this, use of the Carbon Cartridge Kit during the processing of a sample allows for low molecular weight compounds that are not typically captured by an SPE disk such as N-Nitrosodimethylamine (NDMA), Pyridine, and 2-Picoline to be extracted and collected.

The Fast Flow Sediment Disk Holder, when used in conjunction with Horizon Technology’s SPE-DEX 4790 carries out the extraction of the “whole” particulate-laden sample.

The Horizon Technology SPE-DEX® 4790 Automated Extraction System, with the Envision® Platform Controller, DryVap® Concentration System, and the Reclaimer™ Solvent Recovery System.

Instrumentation

  • Horizon Technology

- SPE-DEX® 4790 Automated Extractor System

- Envision® Platform

- Dual pH Kit

- Carbon Cartridge Kit

- Carbon Cartridge

- Atlantic™ HLB-H or HLB-M SPE Disk (47 mm)

- Atlantic™ 100 mm, Fine Prefilter

- Atlantic™ 100 mm, Coarse Prefilter

- Fast Flow Sediment Disk Holder

- DryVap® Concentrator System

- DryDisk® Separation Membranes

- Reclaimer™ (Solvent Recovery System)

  • Agilent

- 6890 GC

- 5973 Mass Selective Detector

  • Column: DB-5MS, 30 m x 0.25 mm ID, 0.25 um

Method Summary

System Setup

1. Install the Dual pH Kit:

a. Disconnect the Water-to-Waste line on the back of the extractor.

b. Connect one end of the yellow line to the extractor port labeled Water Waste.

c. Connect one end of the green line to the Water-to- Waste line and the other end to the yellow line connected in step 2. c.

2. Install the Carbon Cartridge Kit:

a. Mount the carbon cartridge perch to the side of the extractor shelf by tightening the thumbscrew.

pH 2 Extraction

  1. Adjust a 1 L aqueous sample to pH 2 with HCl, cap the bottle and mix.
  2. Spike 8270 surrogate into the sample.
  3. Spike 8270 compounds into the sample (50 μg/ml spike was used).
  4. Place an EZ SEAL or a small piece of aluminum foil over the opening of the bottle and screw on the bottle cap adaptor.
  5. Attach the appropriate end of the yellow Dual pH line to the water recollection bottle.
  6. Attach the appropriate end of the green Dual pH line to the water recollection bottle.
  7. Load the Fast Flow Sediment Disk Holder with an Atlantic HLB-H or an HLB-M 47 mm disk and Atlantic Prefilters.
    Table 1: The 8270D Acidic & Basic Extractor Method For 8 Second Rinses.
  8. Lower the Disk Platform and install the set screws into the appropriate holes.
  9. Place the magnet over the sensor to achieve an 8 second rinse.
  10. Place a clean receiver labeled as the acidic extract onto the extractor. For the 8 second rinse, use a 125 mL Erlenmeyer flask or equivalent receiver.
  11. Load the acidified sample on the SPE-DEX 4790 making sure to puncture the foil enough to ensure proper flow.
  12.  Start the EPA Method 8270D extraction method in Table 1, for the 8 second rinse method.
  13. Collect the acidic extract.

pH 12 Extraction

  1. Using the white Tube Clamp on the green Dual pH line, clamp off the vacuum so other extractors are not affected.
  2. Remove the top from the recollected water bottle.
  3. Adjust the recollected water to pH 12 with NaOH and mix.
  4. Press the cap into the top of the Carbon Cartridge.
  5. Insert the Carbon Cartridge assembly into the perch.
  6. Attach the green Dual pH water waste line to the cap on the Carbon Cartridge.
  7. Attach the yellow Dual pH line to the tip of the Carbon Cartridge.
  8. Un-clamp the green Dual pH line.
  9. Place a clean receiver labeled as the basic extract on the extractor. For the 8 second rinse, use a 125 mL Erlenmeyer flask or equivalent receiver.
  10. Place an EZ SEAL or a piece of aluminum foil and the bottle cap adaptor onto the pH 12 sample bottle and load onto the SPE-DEX 4790.
  11. Ensure that the magnet is still over the sensor to achieve an 8 second rinse.
  12. If there is a heavy buildup of sediment in the disk holder, replace the used Atlantic Prefilters with fresh Prefilters.
  13. Using the same Atlantic HLB-H or HLB-M disk as in the acidic extraction, start the 8270D extraction method in Table 1 for the 8 second rinse method.
  14. Collect the basic extract.

Cartridge Elution

  1. Remove the disk holder with the Atlantic HLB-H or HLB-M disk from the SPE-DEX 4790 platform.
  2. Disconnect the lines from the Carbon Cartridge and remove it from the perch.
  3. Connect the yellow Dual pH line to the green Dual pH line.
  4. Remove the cap from the Carbon Cartridge and install the funnel in its place.
  5. Install the Carbon Cartridge and funnel assembly onto the SPE-DEX 4790 for elution.
    6. Table 2: 8270D Carbon Cartridge Extractor Method For 8 Second Rinses.
  6. Place a clean receiver labeled as the carbon extract on the extractor. For the 8 second rinse, use a 125 mL Erlenmeyer flask or equivalent receiver.
  7. Ensure that the magnet is still over the sensor to achieve an 8 second rinse.
  8. Extract using the 8270D Carbon Cartridge Method shown in either Table 2 for the 8 second rinse.

Concentration

Table 3: DryVap Conditions.
  1. Assemble the DryDisk reservoir using a DryDisk Separation Membrane and load the reservoir onto the DryVap
  2. Set the conditions as shown in Table 3.
  3. Start the concentration process by adding the acid extract into the DryDisk reservoir.
  4. Allow the acidic extract to filter through the DryDisk into the Concentrator tube.
  5. Manually rinse the Erlenmeyer flask with methylene chloride adding this to the DryDisk reservoir, allowing the rinse solvent to process through the DryDisk. Do this three times.
  6. Manually rinse the DryDisk reservoir with methylene chloride and allow the solvent to filter through the DryDisk. Do this three times.
  7. When the methylene chloride has filtered into the concentration tube press stop on the DryVap.
  8. Remove the DryDisk reservoir from the DryVap and empty the acidic water into the appropriate waste container.
  9. Without disassembling the DryDisk reservoir, rinse the reservoir with acetone and discard it into the appropriate waste container
  10. Rinse the DryDisk reservoir with methylene chloride, discarding the rinsate into the appropriate waste container.
  11. Load the DryDisk reservoir back onto the DryVap and follow steps 3 to 6 for the base extract.
  12. When the base extract has processed through the DryDisk, allow the station to transition to the heat stage.
  13. When the volume has concentrated to a point where there is enough volume within the concentrator tube for the carbon extract, press stop on the DryVap.
  14. Process the carbon extracts using steps 3 through 6 and the conditions in Table 3.
  15. Allow the DryVap to concentrate the extract to less than 0.9 mL.
  16. Using 0.2 mL of methylene chloride, rinse the heater and the flat portion of the concentrator tube.
  17. Bring the extract up to a final volume of 1.0 mL.
  18. Transfer the extract to a GC vial. And analyze by GC/MS using the conditions in the section labeled GC/MS Method.

GC/MS Method

Results

Table 4 illustrates the results of the 8 second rinse method for the Fast Flow Sediment Disk Holder with the Atlantic HLB-H SPE Disk and Atlantic Fine Prefilter. For all 114 compounds that were examined within this study, recoveries averaged 85% with 3.97% RSD. All RSDs calculated fell below 11%.

Table 4: EPA Method 8270D Recoveries for the 8 Second Rinse Mode with Atlantic HLB-H SPE Disk

Table 5 shows the data obtained when using the Atlantic HLB-M SPE Disk and Atlantic Fine Prefilter with the Fast Flow Sediment Disk Holder in its 8 second rinse mode. All recoveries averaged 86%, with an average RSD of 3.74%. The calculated RSDs all fell below 20%, with the exception of Aniline, which had an RSD of 28%. This is primarily due to the decreased amount of sorbent contained within the Atlantic HLB-M SPE Disk. For better precision and recovery of Aniline, it is recommended that the Atlantic HLB-H disk be used.

Table 5: EPA Method 8270D Recoveries for the 8 Second Rinse Mode with Atlantic HLB-M SPE Disk

Conclusions

The data demonstrates that Horizon Technology’s Fast Flow Sediment Disk Holder, Atlantic HLB-H and HLB-M SPE Disks and Carbon Cartridges are capable of fully automating the extraction of semi-volatiles for EPA Method 8270D, resulting in excellent data. Final extraction volumes averaged 100 mL of total solvent to be concentrated. Extraction times averaged 128 minutes while drying and concentrating times were approximately 40 minutes. The SPE-DEX 4790 Automated Extractor System with the Envision Platform, DryVap Concentrator System and Reclaimer SRS is shown to reduce analyst labor, solvent usage, turnaround time, while improving both accuracy and precision.

Please check out our Automated Solid Phase Extraction System (SPE System) section for more information or to find manufacturers that sell these products.

References

  1. Method 8270D Semi volatile Organic Compounds by Gas Chromatography/Mass Spectrometry (GC/MS). U.S. Environmental Protection Agency, January 1998, Revision 4