## 2 Biosorbent-Based Extraction Phases
### Bract as a Biosorbent  
Another lignocellulosic material was reported in 2017 as a green extraction phase for SPME [20]. The material, called bract, is the non-developed seeds obtained from the tree _Araucaria angustifolia_ ([PERSON], a conifer found in the south and southeast of Brazil and in eastern Argentina. This material is composed of 45% lignin, 46% holocellulose (cellulose and hemicellulose) and 15% total extractives. The process for obtaining bract-based fibers is similar to those already described for cork fibers. Both materials are similar; however, the cork powder presents a better attachment to the nitinol wire, so it is easier to handle. Bract has been used as an environmentally friendly and low-cost biosorbent coating for SPME for the determination of OCPs in river and lake water [20] and PAH's in river water [21] (Table 1). The characterization of bract fiber carried out by thermogravimetric analysis (TGA), SEM and FTIR showed that the fiber offers satisfactory thermal stability with no decomposition observed up to 260 \({}^{\circ}\)C. SEM micrographs presented a highly porous and rough morphology and a film thickness of approximately 60 \(\upmu\)m [20]. Like cork, bract is also a lignocellulosic material. The FTIR spectrum revealed peaks related to O-H bond and C-H stretching assigned to polysaccharides and lignin. C=C stretching from the aromatic rings and a peak related to C-O-C bond were also identified. Figure 2 shows a scheme of the preparation (2A) and SEM micrographs obtained for bract SPME fiber (2B).  
When applied to the determination of OCPs in water samples by gas chromatography-electron capture detection (GC-ECD), a satisfactory analytical performance was reported with limits of detection  
Figure 1: Scheme of the biobased bar-adsorptive microextraction (BA\({}_{\text{H}}\)E) procedure to determine hexanal and heptanal in human urine by HPLC-DAD. Reproduced with permission from [19], Copyright Elsevier, 2017.  
Figure 2: (**2A**) Scheme of the preparation of SPME fibers and (**2B**) SEM micrographs obtained for bract fiber (**a**) magnification of 1500\(\times\) (**b**) magnification of 3000\(\times\) and (**c**) a cross-section of the proposed fiber at magnification of 300\(\times\). Reproduced with permission from [20], Copyright Elsevier, 2017.  
(LODs) ranging from 0.19 to 0.71 ng L\({}^{-1}\). In addition, the biosorbent-based fiber provided efficient extractions when compared with the commercial mixed coating fiber DVB/Car/PDMS. In 2018, bract fiber was used for the determination of PAH's in water samples by gas chromatography-mass spectrometry (GC-MS) [21]. In this study, the LODs varied from 0.003 to 0.03 \(\upmu\)g L\({}^{-1}\) (Table 1).  
Bract has also been used with TFME combined with a 96-well plate for the determination of steroid estrogens in human urine by liquid chromatography fluorescence detector (HPLC-FLD) [22]. At this time, the target compounds presented intermediate polarity with log P \(\leq\) 4.12. The extraction efficiency of the bract layer was explained by the \(\uppi\)-\(\uppi\) interactions between lignin and the analytes. The LODs of the method varied between 0.3 \(\upmu\)g L\({}^{-1}\) for 17-\(\upbeta\)-estradiol and 3 \(\upmu\)g L\({}^{-1}\) for estrone (Table 1). As an advantage, in this study, the authors reported the use of the 96-well plate system, allowing for 1.7 min/sample turnaround times for the proposed method.