A New Automated Solid Phase Extraction Approach for Troublesome Water Samples by Method 8270D

EPA Method 8270D is used to determine a list of up to 243 semi-volatile organic compounds that are neutral, acidic, basic, and are soluble in methylene chloride. Semi-volatile water samples can contain varying amounts of suspended particulates and/or sediment due to either the source of the water, or the collection technique. By elevating the pH of semi-volatile samples, precipitates can form and result in an emulsion that can create problems for an efficient extraction with traditional techniques. These types of samples, due to their sediment content, have historically proven very challenging when using solid phase extraction (SPE).

To meet the demands of the analytical world, an attractive combination was developed consisting of the Fast Flow Sediment Disk Holder and the Atlantic™ One Pass Disk. 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 which is able to extract the large list of semi-volatile compounds without a second pass of the sample at an elevated pH eliminating the formation of precipitates; which in turn leads to troublesome emulsions. These solutions, along with Horizon's SPE-DEX® 4790 Automated Extractor System, streamline the extraction process and allow for all samples to be processed at the same high flow rate without compromising results.

System Setup

1) Adjust 1 L aqueous samples to pH 2 with HCl, cap the bottle and mix.

2) Spike 8270 compounds and surrogates into samples (50 µg/mL spike was used).

a. Place an EZ-Seal over the opening of the bottle and screw on the bottle cap adaptor.

3) Load the Fast Flow Sediment Disk Holder with the Atlantic 8270 One Pass 47 mm disk and Atlantic Prefilters onto the extractor platform.

4) Assemble the carbon cartridge system (Optional extraction step for certain compounds).

5) Ensure the extractor system is at high vacuum (-25 in. Hg).

Sample Processing and Acidic Extraction

1) Place a clean 125 mL Erlenmeyer flask onto the extractor.

2) Load the pH 2 sample onto the extractor.

3) Load and start the acidic extraction method shown in Table I.

4) Cap and label extract as acid fraction.

Table I: Acid extraction method

Ion Exchange Elution

1) Place a clean 125 mL Erlenmeyer flask onto the extractor.

2) Load and start the method shown in Table II.

3) Cap and label the extract as the ion exchange fraction.

Table II: Ion exchange elution method

Carbon Cartridge Elution

1) Remove the Fast Flow Sediment Disk Holder.

2) Disconnect the lines from each end of the carbon cartridge and connect them together.

3) Install the cartridge/funnel assembly onto the SPE-DEX 4790 platform.

4) Place a clean 125 mL Erlenmeyer flask onto the extractor.

5) Load and start the method shown in Table III.

6) Cap and label the extract as carbon fraction.

Table III: Carbon elution method

Concentration

1) Dry then concentrate all three extract fractions to 1.0 mL on the DryVap® Concentration System with direct to GC vial concentrator tubes.

2) Transfer extracts to GC–MS for analysis.

Results

The results for the selected EPA Method 8270D compounds are listed in Table IV. They show an average recovery of 80% and an average relative standard deviation of 5.95% for over 114 compounds for six replicates. The results show that the solution presented will reduce analyst labor, solvent usage, and turn-around-time while maintaining the high quality results required within today's laboratories.

Table IV: Recoveries from six replicates

Table IV: Recoveries from six replicates

Table IV: Recoveries from six replicates

References

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

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