Two-phase HF-LPME

The chemical principle of two-phase HF-LPME is identical to that in the FS- and HF-MMLLE systems discussed in the previous section. Thus, it is merely a case of different names for similar technical approaches. The intention of this section is to give a brief synopsis describing the most recent and important developments in this technique, and its potential automation. 

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For two-phase HF-LPME, the lumen, as well as the porous wall of the fiber, is fiUed with the organic solvent. Since the fibers are hydrophobic, organic solvents easily diffuse through the wall hence, the most convenient way to fill the fibers is to seal them in both ends by heat and place... 

To simplify the above-mentioned MMLLE systems and, unlike the automated flowing MMLLE, the nonautomated, nonflowing design of MMLLE is simple to prepare manually and is an easy-to-use extraction procedure that is always done off-line prior to GC analysis. In this context, only a short piece of HF membrane is employed as an extraction device after the HF lumen and pores96 or only the pores97 have been filled with an appropriate organic solvent, the membrane is immediately immersed in the aqueous sample. The principle of this two-phase HF-MMLLE system is also called HF liquid-phase microextraction (HF-LPME) and will be briefly commented on in the next section. 

The two-phase HF-MMLLE/HF-LPME procedure with potential automation is expected to achieve wide acceptance among researchers and experimentalists as it is direct and easy-to-use. 

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