## 3 Sample Preparation Techniques and Development of Extraction Sorbents
### Liquid-Based Extraction  
Liquid-liquid extraction (LLE) is a conventional extraction technique that involves partitioning between two immiscible phases. LLE offers several advantages, including high-separation factors and high-purity products. However, there are several shortcomings associated with LLE, including being time-consuming, needing a large volume of solvent consumption, being tedious, and formation of emulsion, which could potentially impose health and environmental safety threats [27; 28]. Therefore, recent studies have been primarily centered on miniaturization of LLE to develop facile, quick, and environmentally and economically friendly extraction methods. Hence, miniaturized techniques such as liquid-liquid microextraction (LLME), dispersive liquid-liquid microextraction (DLLME), vortex-assisted liquid-liquid microextraction (VALLME), and single-drop microextraction (SDME) have been developed. LLE required a large volume of sample to obtain low LOD. Thus, modification in LLE has been carried out particularly in terms of organic phase volume reduction into microliters [29; 30; 31]. Table 3 shows the summary of past studies on the application of LLE as sample preparation technique for OPPs' determinations. DLLME was introduced by [PERSON] et al. [32]. Since then, DLLME has been widely used for the extraction of various compounds in liquid samples. In DLLME, an extractant is formed as small droplets of the water-immiscible organic solvent in the sample solution by using water-miscible organic solvent [29]. [PERSON] et al. [33] developed a miniaturized LLE technique known as dispersive liquid-liquid microextraction (DLLME) for the extraction of OPPs from cucumber and watermemol samples prior to gas chromatography flame photometric detection (GC-FPD). The developed method showed satisfactory recovery (67-111%) for all the targeted analytes. A comparative study was performed with conventional LLE to assess the applicability and analytical performance of the developed DLLME method. Results indicated that both DLLME and conventional LLE methods exhibited comparable analytical performance in terms of recovery and precision. Nonetheless, the DLLME method exhibited lower LOD (0.1-0.19 ng g\({}^{-1}\)) in comparison to conventional LLE (0.8-2.0 ng g\({}^{-1}\)). This is because DLLME achieved a higher enrichment factor than conventional LLE. Besides that, the developed DLLME showed advantages over the conventional LLE, by which the volume of organic solvent was substantially reduced and evaporation procedure was eliminated, which, in turn, reduced the analytical process time. However, DLLME possesses major shortcomings in terms of the limitation of solvents' selection, capable of forming a dispersive phase and that primarily consisted of chlorinated solvents [34]. Therefore, a new analytical method was introduced by [PERSON] et al. in 2010 [30; 35], termed as vortex-assisted liquid-liquid microextraction (VALLME) to overcome the drawback of DLLME method. [PERSON] et al. [31] developed a VALLME method for determination of 12 selected OPPs from water and wine samples using gas chromatography-mass spectrometry (GC-MS). The method exhibited low LOD (2-11 ng L\({}^{-1}\)) with good enrichment factors ranging from 65-389. Besides that, satisfactory recoveries (70-120%) were achieved for all the targeted OPPs. The method provides advantages in terms of ease of operation, high enrichment factor, good analytical performance, cost reduction, and eliminating the use of additional dispersing solvents. Thiscould also probably be due to the use of GC-MS as the analytical method since GC is a good tool for the analysis of volatile and easily vaporized compounds. Besides that, MS provides high sensitivity and accuracy, better anti-interference effect, and good reproducibility [12].