The Extraction of Chlorinated Pesticides, Herbicides, and Organohalides for EPA Method 508.1 Using Automated Cartridge SPE

This application note will highlight the extraction of EPA Method 508.1 analytes from an aqueous matrix. It will use the SmartPrep Extractor and the DryVap Concentrator system to achieve excellent recoveries while maintaining minimal user-interface.

Instrumentation

• Horizon Technology:

- SmartPrep™ Extractor (6 mL Configuration; 20 mL Tray)

- Bottle Rinse Kit

- DryVap® Concentration System with DryDisk® Membrane

Phenomenex:

- Strata® C18-E, 6 mL Cartridges

- Zebron™ – MR 1: 30 m × 0.32 mm × 0.50 µm

- Zebron™ – MR 2: 30 m × 0.25 mm × 0.25 µm

Method Summary

1. Prepare 1 L of reagent water using HCl to lower the pH to 2.

2. After mixing, add surrogate solution and spike solution (for blank samples, add only surrogate solution).

3. Attach Sip Tube 1 and Bottle Rinse 7 to the sample container.

4. Place a 20 mL VOA vial in position 1 of the tray.

5. Place a 6 mL C18-E cartridge in position 1 of the carousel.

6. Program and run the EPA 508.1 Method with a N₂P1 pressure of 5 psi and a N₂P2 pressure of 10 psi.

7. Place a 1 mL endpoint Concentration Tube on the DryVap and attach a DryDisk reservoir with a membrane.

8. Transfer the contents of the VOA vial to the DryDisk Reservoir and start the DryVap using a sparge pressure of 20 psi and a vacuum of -10" Hg.

9. Upon completion, bring the volume up to 1 mL using EtOAc, transfer to a vial add internal, and run on a GC-ECD.

Results

A degradation check solution containing DDT and Endrin and was used for every analytical batch.

When performing the analysis, it was discovered that there were multiple sets of co-elutions. On MR-1, a co-elution between Simazine and Atrazine and another between d-BHC and Metribuzin were found. On MR-2, a co-elution between Heptachlor Epoxide B and the surrogate Dibrophenyl was found. In the first case, the co-eluting compounds cannot be reported from the MR-1 column. For MR-2, a different surrogate was selected to clear up the co-elution (Decachlorobiphenyl).

Table I: Average recovery of 12 LCS extracts

The average recovery for 12 extracts was calculated and is shown in Table I for each column used. With averages of 93% and the highest RSD being 17%, they show excellent results for all the compounds that are able to be reported on each column.

Conclusion

The SmartPrep Extractor Cartridge system was used to extract EPA Method 508.1 compounds from water samples. When coupled with the DryVap Concentration system and DryDisk Separation Membranes, both excellent precision and accuracy was demonstrated. The solutions presented will allow a laboratory to streamline their aqueous extraction procedures and minimize the costs associated with labor and solvent while maintain the level of quality required.