## 5 Directions for the Development and Possibilities of Using Microextraction Techniques
\begin{table}
\begin{tabular}{l|l|l|l|l|} \hline \multicolumn{1}{c|}{**Advantages**} & \multicolumn{1}{c|}{**Disadvantages**} & \multicolumn{1}{c|}{**Technique**} & \multicolumn{1}{c|}{**References**} \\ \hline \(\bullet\) & Requires the use of a small amount of organic solvents & - & & \\ \(\bullet\) & Easy to use & & LLLME & [15] \\ \(\bullet\) & High numerical value of the enrichment coefficient & & & \\ \(\bullet\) & Quick & \(\bullet\) & Relatively expensive (fibre cost) & & \\ \(\bullet\) & Cheap & \(\bullet\) & Limited time of fibre use & & \\ \(\bullet\) & Low analyte losses & \(\bullet\) & Matrix effects & \\ \(\bullet\) & Easy to use & \(\bullet\) & Fibre damage & \(\bullet\) \\ \(\bullet\) & Possibility of implementing an analytical procedure on-line & & & \\ \(\bullet\) & Possibility of using liquid, gaseous and solid samples, & & & \\ \(\bullet\) & High sensitivity, & & & \\ \(\bullet\) & Easy to automate and miniaturize & & & \\ \(\bullet\) & Continuous contact between the solvent drop and a fresh sample solution & - & & \\ \(\bullet\) & Possibility of accurate control of the solvent drop size & & & \\ (combined with HPLC) & & & & \\ \(\bullet\) & High numerical value of the enrichment coefficient & & & \\ \(\bullet\) & Requires the use of a small amount of sample & & \\ \hline \end{tabular}
\end{table} 
Table 5: _Cont._An example can be continuous-flow microextraction. In this technique, just like in the other microextraction techniques, modifications aimed at extending its scope of application have been introduced. Modifications and improvements of this technique allowed to use it in the analytical procedures for the determination of metals in biological and environmental samples. Thus, the new method--IL-based cycle flow SDME combined with ETV-ICP-MS was used for the determination of mercury-containing samples [80,81]. Some of the major areas of concern in terms of innovation and new solutions of microextraction techniques include the use of:  
* electromembrane HF(3)ME extraction (EME) of ionized species;  
In this method, an electrical potential applied across the SLM is used as driving force for creating the flux of uncharged analytes towards the acceptor phase. Furthermore, the extraction is assisted by strong stirring in order to reduce the standing (stagnant) organic layer near the SLM and to induce convection in the sample. After aqueous acceptor extraction, the solution may be transferred directly into the HPLC and CE [13]. At the moment knowledge about EME is limited, and therefore, still more research is carried out to understand the exact extraction mechanism in order to optimise specific analyte extraction conditions/parameters, and to demonstrate that this technique provides reliable data for a wide range of analytical applications. The electrokinetic membrane extraction is an interesting concept which in the future will allow the sample preparation to be integrated with separation techniques [13]. * SME procedures for practical on-line sample analyses;
* solvents less dense than water in DLLME;
* ionic liquids (ILs);
* ultrasound-assisted emulsification for DLLME [19]. Ionic liquids are becoming more popular due to the low consumption of volatile organic solvents and a high rate of enrichment thanks to the use of ultrasound; certain stages of the analytical procedure such as homogenizing, emulsifying or extraction can be accelerated. The combination of ionic liquids and the dispersion by sonication of a liquid-liquid microextraction allowed to design a new method for the extraction--IL-USA-DLLME--which is as fast, simple and effective as the DLLME technique, but does not require the use of organic solvents. Until now, this method \"was proven\" during the determination of cadmium, mercury or phytocides, but it also has the potential for the determination of trace amounts of other metal ions in samples with complex matrices [82,83]. However, not all of these new approaches/solutions have been recognised in the determination of mercury and tin compounds.