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Solid Phase Extraction is an extraction process whereby an aqueous sample is filtered through a bed of sorbent particles. The sorbent particals are usually in the form of a disk or a cartridge. Analytes of interest are removed from the aqueous sample, and concentrated onto the sorbent. Once concentrated, the analytes are removed from the sorbent by a series of eluting solvent rinses.
Solid Phase Extraction methods offer significant advantages over traditional Liquid-Liquid Extraction (LLE) techniques.
- SPE uses less solvent than a typical LLE procedure
- SPE is faster; only 20-30 min for a 1-liter sample
- SPE costs considerably less than LLE
- SPE provides comparable / better recoveries than LLE
- EPA Methods are constantly being developed for SPE
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Comparison of LLE and SPE Disk Methods
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| LLE |
SPE Disk |
| Uses 200 to 500 mL of solvent |
Uses 20 to 30 mL of solvent |
| Shaking/continuous process |
Filtration process |
| Forms emulsions and surfactants |
No emulsions formed |
| Limited selectivity |
Wide selectivity (absorbant) |
| Requires solvent removal |
Optional |
| Two hours per sample |
20 minutes per sample |
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