Solid Phase Extraction (SPE)

Principle of Extraction

1. Solid Phase Extraction (SPE)

This extraction method involves the application of the selective partitioning of the compounds between a solvent, as the liquid phase and a sorbent, as the solid phase to separate or remove the extracted compound or analyte from the compound mixtures. In other words, it involves the affinity of solutes of the liquid solvent to the solid adsorbent or also known as the stationary phase. Thus, it involves reversible and strong interactions between both analytical compound and the stationary phase. The procedures applied in this technique includes solvation, conditioning, loading, washing and elution of compound. (2)

(i) Solid Phase Micro-Extraction (SPME or Spee Mee)

SPME is a solvent free

Generally, the 2 immiscible phases are aqueous and organic solvent. Besides, it can be stated as the ratio, K, where solubility of analyte dissolved in organic phase (g/100ml) to the solubility of solute dissolved in aqueous phase (g/100ml).

3. Hot Continuous Extraction (Soxhlet)

This is a continuous extraction method using a hot solvent, which the extracting phase will be passed continuously through the sample until it achieves a quantitative extraction. This method is usually applied on the compounds of unfavorable partition coefficient which means the desired compound is insoluble in the solvent. (4)

4. Ultrasound-assisted Extraction (UAE) or Sonication Extraction

This extraction technique applies the ultrasound of the frequencies between 2kHz and 2000kHz, which increases the permeability of cell walls as well as contacting surfaces of samples and solvent and thus produces cavitation. This method is useful in extracting not only small scale but also larger scale of compounds.

Therefore, a supercritical fluid shows both gas and liquid characteristics. The use of supercritical fluid has variety benefits if compared with other normal liquid solvents. The supercritical fluid increases the mass transfer due to its high diffusion coefficient, low surface tension and also low viscosity. With these properties, the supercritical fluid is suitable for thermolabile compounds. Therefore, damages on the chemical constituents can be avoided due to SFE works under low temperature. Moreover, this fluid can be regenerated by adjusting pressure and recycled thus it is said to be environmental friendly extraction method. Generally, the fluid used in this method is carbon dioxide, CO2. However, this extraction technique usually requires a longer time in extracting