Streamlining Sample Processing for Semi-Volatile Organics in the Most Challenging Water Samples

Laboratories taking in a high volume of aqueous semi-volatile samples know that every sample is different. Samples can contain varying amounts of suspended particulates and/or sediment due to either the source of the water, or the collection technique. Still other samples may form flocculates under elevated pH conditions resulting in emulsions when agitated in techniques such as liquid-liquid extraction (LLE). These types of samples have historically also proven challenging when using solid phase extraction (SPE).

To meet the demands of this challenging type of sample, a new extraction method only requiring the sample to be acidic to extract over 100 routine compounds has been developed. This method uses SPE technology with an economical and effective extended disk holder. The Fast Flow Sediment Disk Holder allows laboratories to use an economical 47-mm SPE disk while still maintaining the use of a 100 mm prefilter. The Atlantic 8270 One Pass Disk contains sorbent that is able to extract the large list of semi-volatile compounds without a second extraction at an elevated pH, eliminating the formation of flocculates.

This work examines the procedure and performance characteristics of this simplified extraction process.

Figure 1 shows the extraction process using the one-pass disk and a carbon cartridge.

Figure 1: SPE extraction scheme.

Results and Discussion

Six extractions were performed, each extraction took approximately 120 min to complete. Of this time, a maximum of 10 min of analyst time was taken from start to finish interacting with the samples.

Figure 2 shows the results on a large suite of compounds found in the US EPA 8270 list. The results show that, with an average recovery of 80% and an average relative standard deviation of 5.95% over 114 compounds, the automated SPE methodology presented is an excellent alternative for extracting USEPA 8270 semi-volatile compounds from aqueous samples.

Figure 2: Average recovery of six replicate extractions for a large suite of compounds.

The key to this methodology was the Atlantic 8270 One Pass Disk. The disk's unique sorbent was able to extract a large list of semi-volatile compounds without a second pass of the sample at an elevated pH. Each extract was automatically dried and concentrated using the DryVap® System. By concentrating extracts under vacuum it lowered the boiling point ensuring the more volatile semivolatiles were not boiled off and ensures higher recoveries.

Conclusions

The data presented clearly illustrates this automated SPE methodology is capable of successfully extracting over 100 compounds specified by EPA method 8270.

• The single pH extraction eliminates the need to basify the sample, reducing the chance of flocculates and resulting low recoveries.

• This new SPE methodology for semi-volatiles streamlines the extraction process and allows for all types of aqueous samples to be processed at the same high flow rate.

• This automated SPE methodology is a solution that will reduce analyst labor, solvent usage, and turn-around-time while maintaining the high quality results required within today's laboratories.

References

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

(2) D. Gallagher, J. Fenster, M. Ebitson, and J.McGettrick, "Streamlining Sample Processing for Semi-Volatile Organics Using the Fast Flow Sediment Disk Holder and the Atlantic 8270 One Pass Disk," Application Note 069, Horizon Technology, Inc., 2011.

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