Automated Solid Phase Extraction (SPE) of Organochlorine Pesticides in Water

Organochlorine pesticides are man-made organic chemicals with a history of wide spread use in both the United States as well as globally. Tending to be very persistent in the environment, they have found their way into sediments and drinking water supplies posing serious health risks. Organochlorines have a wide range of both acute and chronic health effects, including cancer, neurological damage, and birth defects. Many organochlorines are also suspected endocrine disruptors.

Figure 1: PowerPrep SPE and SuperVap Concentrator systems.

In response to growing health concerns, the United States has banned several of these compounds such as DDT, dieldrin and chlordane. Others are still in use including lindane, endosulfan and methoxychlor.

Liquid-liquid extraction via a sep-funnel is the traditional method used for the extraction of organochlorine pesticides. Not only is it time consuming, it also requires a large volume of chlorinated solvent. The result is high cost and low reproducibility. The automated, solid phase extraction method described below allows for rapid, reproducible extractions using a minimal volume of solvent that produce consistent results.

Table I: Mean recovery and standard deviation for five replicates

Instrumentation

• FMS, Inc. PowerPrep™ SPE (solid phase extraction) system

• FMS, Inc. SuperVap™ Concentration

• FMS, direct-to-vial concentrator tubes

• 1 g C18 cartridges

• Agilent 7890A GC with uECD

PowerPrep SPE

1. The C18 Cartridge is conditioned with 10 mL methanol

2. The C18 Cartridge is conditioned with 10 mL DI H₂O

3. The sample is loaded onto the C18 Cartridge via vacuum

4. The sample bottle auto rinsed loaded on to the C18 cartridge

5. The C18 cartridge is dried with nitrogen

6. Elute with methylene chloride

SuperVap Concentrator

1. Pre-heat temp: 65 °C; 2. Pre-heat time: 30 min; 3. Heat in Sensor mode: 65 °C; 4. Nitrogen Pressure: 15 PSI

Procedure: Sample Prep and Extraction

1. Five, 1 L water samples spiked with 1 mL EPA 8081 surrogate spiking solution (2 analytes)

2. Samples were spiked with EPA 8081 pesticide spiking solution (20 analytes)

3. Samples allowed to equilibrate for 15 min

4. Five samples were loaded onto to corresponding sample ports on FMS PowerPrep SPE system.

5. The program is initiated to run each sample sequentially.

6. The sample is extracted and automatically transferred to the FMS SuperVap Concentrator with direct-to-vial vessels.

7. The sxtracts are concentrated using the SuperVap system to 1 mL exchanged to hexane (15 mLs) and re-evaporated to 1 mL.

8. The extract is removed from the SuperVap system and transferred to Agilent GC for analysis.

Conclusions

The results of five water samples demonstrate the ability of the FMS PowerPrep SPE system to deliver accurate results with excellent reproducibility. The automated SPE Direct to Vial Concentration method described is superior to traditional, time-consuming, inconsistent and expensive liquid-liquid extractions. The addition of the FMS SuperVap system equipped with direct-to-vial tubes enables the transfer of samples directly from sample bottles to GC vials in a single extraction process without handling the extract allows the extract to go directly to the GC for analysis.

FMS Inc.

580 Pleasant Street, Watertown, MA 02472

tel. (617) 393-2396, fax (617) 393-0194:

Website: fmsenvironmental.com