Table 1.
Features of new techniques of on-line biological sample processing.
| Pretreatment technique | Mechanism | Application | Characteristic | Ref |
|---|---|---|---|---|
| SPE | Non-polar effect, polar effects, ionic and covalent effect | Firstly extraction of urine samples of drug abuse; analyzing prostaglandin level in human serum | Good accuracy, precision and recovery; no emulsification and damage compared with conventional LLE | 7, 8 |
| SPME | Evolved from SPE technique; a fused silica fiber surface coated with adsorbed material | Extremely complex mixture such as blood plasma, whole blood, urine and tissue | Small volume of solvent compared with LLE and SPM; promoting the development for the analysis of endogenous and exogenous compounds | 19 |
| Column switching technique | Change through a valve to the mobile phase system, then eluent go from the pre-column into the analytical column | Complex biological matrices such as serum, blood, plasma, urine; environmental protection, pesticide residue monitoring, food inspection | Good resolution and higher selectivity compared with traditional method | 30, 31, 32, 33 |
| RAM | Based on the size exclusion principle | Removal of endogenous macromolecules in biological matrices | Longer lifetime, higher efficiency, higher analyte recovery, lower organic waste, lower total costs compared to traditional SPE sorbents | 37 |
| TFC | Column filled with adsorption material of large particle size | Removal of macromolecular proteins | A high flow rate to extract and remove the interference in the matrix | 43 |
| MIP | Synthesizing materials with specific molecular recognition properties | Identification and determination of low concentration compounds in complex matrices | High mechanical, thermal and pressure stability, but influenced by sample solvent | 56 |
| MD | Perfuse MD probe under the non-equilibrium conditions | Monitoring physiological levels of the active substances in the animal and human | A novel miniaturized sample pretreatment technique; consuming no solvent and achieving good sensitivity compared with SPE and LLE. | 64 |
LLE, liquid–liquid extraction; MD, micro-dialysis; MIP, molecularly imprinted polymers; RAM, restricted access material; SPE, solid phase extraction; SPME, solid phase micro-extraction; TFC, turbulent-flow chromatography.