# Applications of Graphene-Based Nanomaterials in Environmental Analysis
## 4 Conclusions  
The usage of the different graphene-based nanomaterials and nanocomposites in the removal of organic pollutants or metal ions from a variety of environmental water samples is on the rise due to the many advantages they provide versus the commonly used sorbents, such as high sorption capacity, many cycles of reusability, extraordinary active surface area, high chemical and mechanical endurance, and facile handling.  
The main downside these materials demonstrate is the potential aggregation and the piling up of the nanosheets, which might cause blockage to its active adsorption groups. So as to overwhelm this setback, a wide range of functional groups that help to prevent the problem have been recommended and assessed. By improving the dispersibility of the sorbent, its extraction efficiency and the selectivity towards the target compounds, functionalization is enhanced as well. Moreover, in order to be used at an industrial level, more facile and inexpensive preparation pathways have to be introduced, that lead to recyclable and reusable materials.  
As seen, most applications of these materials are fixated on SPE, MSPE and dSPE. Forthcoming developments involve the utilization of graphene-based materials and nanocomposites in other emerging extraction techniques, such as SPME (especially in HF-SPME), PT-SPE and SBSE. More and more new development paths are studied, that are greener or more specific in order to adsorb certain groups of compounds and be selective or to maximize their adsorption capacity. In the foreseeable future, these sorbents will be expected to play a vital part in the extraction of pollutants from environmental samples, whilst new and more specialized materials are synthesized and studied.  
Conceptualization, V.S. and E.D.; methodology, V.S. and E.D.; investigation, O.-E.P., V.S. and E.D.; writing--original draft preparation, O.-E.P., V.S. and E.D.; writing--review and editing, O.-E.P., V.S. and E.D.; supervision E.D. and V.S. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
The authors declare no conflict of interest.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**adsorbent** & **Analyte(s)** & **Applications** & **Sample Preparation** & **Analytical Technique** & **LODs** & **EF** & **Reference** \\ \hline mGO-DVB-VA & \begin{tabular}{c} Pb(II), Cd(II), \\ Cu(II), Ni(II), Co(II) \\ \end{tabular} & Waste water & MSPE & FAAS & 0.37–2.39 \(\mu\)g/L & 40 & [86] \\  & \begin{tabular}{c} River, tannery and \\ electroplating \\ waste water \\ \end{tabular} & d-MSPE & FAAS & 5.2, 1.6 \(\mu\)g/L & 10 & [87] \\ mGO & \begin{tabular}{c} Imatinib, \\ Doxorubicin \\ 2,4,6- \\ trinitrotoluene \\ mGO-MBT 2 \\ \end{tabular} & \begin{tabular}{c} Wall, waste water \\ \end{tabular} & MSPE & HPLC-UV & 1.9, 1.8 \(\mu\)g/L & N/R & [88] \\  & \begin{tabular}{c} Reservoir, drinking, \\ waste water \\ \end{tabular} & MSPE & HPLC-UV & 0.3 \(\mu\)g/L & 153 & [89] \\  & \begin{tabular}{c} Pd(II), \\ Pd(II) \\ \end{tabular} & Tap, lake, sea water & MSPE & FAAS & 0.19, 0.35, & 400 & [90] \\ mGO-HQ 3 & Cd(II), Pb(II) & Water samples & MSPE & FAAS & 0.09, 0.27 \(\mu\)g/L & 130.43 & [91] \\  & \begin{tabular}{c} Cu(II), Cr(III), \\ Zn(II), Cd(II), \\ Pb(II) \\ \end{tabular} & Well, river, bottled & MSPE & FAAS & 0.15–0.65 \(\mu\)g/L & 36–44 & [92] \\  & \begin{tabular}{c} Au(II), Pd(II), \\ Ag(II) \\ \end{tabular} & Waste water & MSPE & FI-ICP-OES & 45–76 ng/L & \begin{tabular}{c} 160, 160, \\ 140 \\ \end{tabular} & [93] \\  & \
\begin{tabular}{c} Cr(III), Cr(VI) \\ \end{tabular} & Waste water & MSPE & ETAAS & 1.9 ng/L & 357 & [94] \\  &
\begin{tabular}{c} di-2-ethylhexyl \\ phthalate \\ \end{tabular} & Water samples & MSPE & HPLC-DAD & 0.35 \(\mu\)g/L & 100 & [95] \\ \hline \hline \end{tabular}  
* Cold Vapor Atomic Absorption Spectrometry, 2 Magnetic Graphene Oxide modified with 2-mercaptoethanolthiazole, 3 Magnetic Graphene Oxide modified with 8-hydroxyquinoline.  
\end{table}
Table 2: _Cont._