# Applications of Graphene-Based Nanomaterials in Environmental Analysis
## 3 Analytical Applications in Environmental Samples
### Applications of GO-Fe\({}_{3}\)O\({}_{4}\)
[86] synthesized and characterized an allylamine modified mGO-poly (vinyl acetate-co-divinylbenzene) (mGO-DVB-VA) and used in the MSPE of Pb(II), Cu(II), Ni(II), Cd(II), and Co(II) for their determination by FAAS. The preconcentration is 40 for all the metal ions and the LODs are 0.37-2.39 \(\mathrm{\SIUnitSymbolMicro g}\)/L. This method was applied to wastewater samples. [PERSON] et al. [87] presented a quick and sensitive method for sequential speciation and separation of Cr(VI) and Cr(III) using d-MSPE for their determination by FAAS, with a triethylenetetramine-modified mGO (mf-GO) as a sorbent from river water samples, tannery wastewater and electroplating wastewater. The use of this sorbent results in the fast removal of Cr(VI) and of Cr(III), which is 10 and 30 min, respectively, while its adsorption capacity is 16.4 and 9.6 mg/g. The speciation is achieved by adjusting the value of the pH. The LODs of the two ions are 1.6 and 5.2 \(\mathrm{\SIUnitSymbolMicro g}\)/L, respectively and the recoveries of spiked analyte samples ranged between 96-102%. [PERSON] et al. [88] extracted imatinib and doxorubicin as cytostatic drugs from environmental water samples by using mGO nanocomposites as a sorbent for MSPE, prior to HPLC-UV analysis. After optimizing the conditions (sample pH, amount of MNPs, the effect of salt concentration and etc. ), the LODs of the two drugs were 1.9 and 1.8 ng/mL, respectively, while their recoveries were 88.4% and 96.7%. [PERSON] et al. [89] also used mGO as a sorbent for the MSPE of 2,4,6-trinitrotoluene in different water samples, determined by HPLC-UV. The optimal MSPE conditions reported were 0.04 g of the nanocomposite, 10 min of extraction by vortexing, 1 mL of ACN as eluent, and 6 min of desorption by ultrasonication. The method exhibited 0.3 \(\mathrm{\SIUnitSymbolMicro g}\)/L as the LOD, while the recovery values from the reservoir, drinking water and effluent wastewater samples were 87-120%. [PERSON] et al. [90, 91] proposed two different methods regarding the usage of mGO in MSPE. The first one dealt with the determination of trace amounts of Cd(II), Pb(II) and Cu(II) ions by FAAS by utilizing a modified mGO with 2-mercaptoethanolhazole. Under optimum conditions, the LODs of the three metal ions were calculated to be 0.19, 0.24 and 0.35 ng/mL, respectively. The second method consisted of the synthesis of mGO modified with 8-hydroxyquinoline and its use for the extraction and preconcentration traces of Cd(II) and Pb(II) ions. The LODs were 0.09 and 0.27 ng/mL and the enrichment factor was obtained at 130.43. [PERSON] et al. [92] demonstrated the preparation SiO\({}_{2}\)-coated mGO modified with polypyrrole-polythiophene (mGO/SiO\({}_{2}\)@coPPy-Th) for its use as an ideal sorbent for the determination of trace levels of Cu(II), Zn(II), Cr(III), Pb(II) and Cd(II) from well, river and bottled mineral water samples prior to FAAS analysis. The recoveries of the metal ions varied from 90% to 106%, the LODs ranged from 0.15-0.65 ng/mL and the preconcentration factor was defined as 36-44 for the five metals. [PERSON] et al. [93] modified an mGO with 2-mercaptoethanolhazole for the selective MSPE of Au(III), Pd(II) and Ag(I). The metal ions' desorption was done with a solution of thiourea and then the ions were determined by flow injection coupled with ICP-OES (FI-ICP-OES). Effects of sample volume and pH, volume and type of eluent, amount of sorbent and time of adsorption and desorption were considered. Under the optimal conditions, the method exhibited 45-76 ng/L LODs, with enrichment factor of 160, 160 and 140 for the three metal ions respectively. [PERSON] et al. [94] synthesized a novel imidazolium-functionalized mGO nanocomposite in the MSPE for the determination of very low amounts of Cr(VI) and Cr(III) species by electrothermal atomic absorption spectrometry (ETAAS) in wastewater samples.