## 2 Biosorbent-Based Extraction Phases
### Other Materials Used as Biosorbents  
A range of other materials characterized as biosorbents have also been used in combination with microextraction techniques for organic compound determination. Although there are still few applications involving these materials, a brief description is provided, along with the existent applications.  
Bamboo plants are characterized by rapid growth and are widely distributed in China. Bamboo charcoal is obtained by submitting the bamboo to high temperatures (over 800 \({}^{\circ}\)C), producing a material with high density, porous structure and a large surface area. Bamboo charcoal was proposed as a novel and inexpensive SPME coating material for determination of 11 phthalate esters (PAE) in water samples by GC-MS [26].  
Another material used as a biosorbent was obtained from powdered seeds of the _Moringa oleifera_ tree. This material is considered to possess a highly fibrous and naturally functionalized surface. The characterization of the moringa-based biosorbent using SEM and FITR showed a porous framework of interconnected fibers, and various functional moieties were identified such as O-H, N-H and C-H and CH\({}_{2}\) groups. The first application for organic compound determination was in 2016, as a sorbent for the determination of 13 phthalate esters (PE) in a milk sample by micro-solid phase extraction (\(\upmu\)-SPE) and GC-MS [27]. The relative polar PEs interacted with the sorbent through the functional moieties identified. The more the alkyl chain of PEs increased, the lower the extraction efficiency became.  
An eco-material denominated montmorillonite (MMT) clay, modified through the intercalation of ionic liquids (IL), has also been applied in the extraction phase [28; 29]. MMT is a clay mineral composed of structural layers consisting of an octahedral alumina sheet sandwiched between two tetrahedral silica sheets. MMT is found in sediments, soils or rock and has been modified to adsorb organic compounds of low polarity from aqueous solutions. In 2016, [PERSON] et al. [28] used rotating-disk sorptive extraction (RDSE) and MMT in the extraction phase for the determination of polychlorinated biphenyl (PCB) compounds in water samples with GC-ECD (Table 1). The RDSE device consists of a rotating Teflon disk containing an embedded miniature magnetic stirring bar. In this study, SEM was employed to characterize the novel sorbent, and the results showed clusters of particles with a narrow size distribution of approximately 25 mm. The extraction efficiency achieved for the MMT modified with 1-hexadecyl-3-methylimidazolium bromide (HDMIM-Br) phase was compared with commercial phases and showed the highest response for all the studied analytes.  
Very recently, the viability of MMT-HDMIM-Br as a green sorbent for RDSE was again investigated [29]. In this study, cork and montmorillonite clay modified with ionic liquid were explored for the determination of parabens in water samples by high-performance liquid chromatography--tandem mass spectrometry (LC-MS/MS). The proposed method presented limits of detection of 0.24 \(\upmu\)g L\({}^{-1}\) for the cork and 0.90 \(\upmu\)g L\({}^{-1}\) for the MMT-HDMIM-Br with correlation coefficients higher than 0.9939 for both biosorbents.