The Automated Extraction of Aqueous Samples by Method EPA 8270D Using the TurboTrace ABN SPE System
EPA 8270D calls for the extraction for analysis of semi-volatile analytes in various matrices. Target analytes mentioned in the method cover a wide range of compound classes resulting in reporting lists that often approach 100 compounds.
EPA 8270D calls for the extraction for analysis of semi-volatile analytes in various matrices. Target analytes mentioned in the method cover a wide range of compound classes resulting in reporting lists that often approach 100 compounds. In aqueous samples, the combination of compound groups such as phenols, analines, PAHs, phthalates, explosives, pesticides, n-nitrosoamines, and others results in a tedious process of multiple liquid-liquid extractions (LLE) with multiple pH adjustments to extract all the analytes. Large elution volumes (>360 mL of methylene chloride) combined with highly volatile analytes, usually result in low recoveries of target compounds and poor analytical precision.
The use of solid phase extraction (SPE) to automate the extraction process can drastically reduce many of the challenges traditional 8270 extractions pose. By automating the process with the FMS ABN SPE system, extraction chemists, normally confined to a hood shaking separatory funnels, can be freed up to perform additional tasks.
Figure 1: FMS TurboTrace SPE system with the SuperVap concentrator.
Instrumentation and Consumables Instrumentation
- FMS, Inc. TurboTrace™ ABN SPE system
- FMS, Inc. SuperVap™ Concentrator
- FMS, Inc. 200 mL concentrator tubes
Consumables
- Fisher Pesticide Optima* Methylene Chloride
- Fisher Anhydrous Sodium Sulfate
- Fisher Optima* Methanol
- Fisher HPLC Grade Water
- FMS 1 gram DVB Cartridges
- Fisher Concentrated Sulfuric Acid
- Fisher Sodium Hydroxide
- Restek Resprep 2 gram coconut charcoal cartridges (Cat# 26032)
- Restek 8270 matrix spike (Cat# 33073)
- Restek SV Internal Standard Mix (Cat# 31006)
- Restek B/N Surrogate (Cat# 31024)
- Restek Acid Surrogate (Cat# 31025)
- Restek Benzidines mix (Cat# 31834)
Procedure
Prepare 1 L samples of DI water
Adjust pH of samples to <2 by adding H2SO4 drop wise.
Spike samples with 8270 matrix spike, B/N surrogate, and acid surrogate spiking solutions
Load samples onto FMS TurboTrace ABN SPE system.
Affix collection bottle to retain post extraction aqueous sample.
Affix coconut charcoal and DVB with pre-filter cartridges to TurboTrace ABN system.
SPE
1. Cartridges pre-wet with DCM
2. Cartridges conditioned with MeOH
3. Cartridges conditioned with H2O
4. Samples passed across DVB cartridges at ~20 mL/min via vacuum
5. Cartridges partially dried with N2 at 15 PSI
6. Sample bottles sprayed with DCM
7. DCM bottle spray loaded across cartridge and collected throughin-line NaSO4
8. Cartridges eluted with additional 10 mL DCM
9. Cartridges purged with N2 eluting n-Hexane directly to FMS SuperVap concentrator
10. Remove aqueous collection bottle and add NaOH solution to sample mixing thoroughly till pH is >12
11. Attached sample bottle to system for second pass
12. DVB Cartridge re-conditioned with MeOH
13. DVB Cartridge re-conditioned with H2O
14. Sample passed across both cartridges at ~10 mL/min
15. Cartridges dried with N2 for 1 min each
16. Sample bottle sprayed with DCM
17. DCM bottle spray loaded across DVB cartridge and collected through in-line NaSO4
18. DVB Cartridge eluted with additional 5 mL DCM
19. Coconut charcoal eluted with 20 mL DCM
20. Cartridges independently purged of residual solvent via N2 stream
SuperVap Concentrator
1. Preheat temp.: 10 min at 40 °C
2. Evap mode: 40 °C
3. Nitrogen Pressure: 10 PSI
4. Evaporate extracts 1 mL*
*Evaporator tubes manually rinsed with DCM to ensure no target analytes adhere to evaporator tube walls. Internal standard solution added to extract postevaporation for GC–MS analysis.
Conclusions
Evaluation of the performance spikes on the FMS TurboTrace ABN extraction system resulted in average recoveries for nearly all analytes between 70–130%. Combined with the analysis of blank replicates which yielded background concentrations of less than 1 µg/ mL for all analytes, the data, when compared to the performance tables within EPA 8270D, shows that automated solid phase extraction is not only equivalent, but in some cases superior to traditional LLE extractions.
Table I: Results from six 1 L LCS samples (50 µg/L concentration)
Repeatability data gave percent deviations between replicates of less than ±10% for most compounds, and ±20% for all. Fully automated sample loading and eluting of both cartridges independently, and in sequence, eliminates the need to have an extraction chemist separate the cartridges at different stages of the operation. The reduction of human interaction saves time, reduces human error, and produces consistent reproducible results.
When paired with the FMS SuperVap concentrator, the TurboTrace™ ABN SPE system provides complete, automated sample preparation for aqueous samples by EPA 8270D.
FMS, Inc.
580 Pleasant Street, Watertown, MA 02472
tel. (617) 393-2396, fax (617) 393-0194
Website: www.fms-inc.com; Email: onlineinfo@fms-inc.com
