# Applications of Graphene-Based Nanomaterials in Environmental Analysis
## 3 Analytical Applications in Environmental Samples
### Applications of \(G\) and \(G\)
[69] experimented with chemically modified GO with mercapto-groups (GO-S) for the determination of copper, chromium, lead and zinc by ED-XRF in lake, river, mineral, spring and sea waters. The extraction technique used was d-\(\upmu\)SPE. [PERSON] et al. [70] presented a new, rapid, and easy technique, where they exploited the GO nanosheets for the novel separation and preconcentration of coagulating homogeneous dispersive micro solid phase extraction (CHd-\(\upmu\)SPE) of chromium, cadmium and lead in water samples. The LODs were 12, 5 and 35 ng/L respectively, while their recovery rates were 98.0% for both Pb and Cd and 97.2% for Cr. [PERSON] et al. [71] utilized diethylenetriamine-functionalized multi-walled carbon nanotubes (MWCNTs) distributed in graphene oxide colloids for the selective SPE of trace amounts of Cr(III), Mn(II), Pb(II) and Fe(III) ions in wastewater. Inductively coupled plasma with optical emission spectrometry (ICP-OES) was used as a determination method of the above ions. The LODs were found to be 0.16, 0.38, 0.24 and 0.50 ng/mL respectively, while the pre-concentration factor was 75. [PERSON] et al. [72] utilized G-functionalized melamine sponges (GMeS) for the microextraction of sulfonamides from environmental samples. The GMeS was prepared by a facile procedure containing only one step, complying with the principles of green chemistry. Lake water samples were adjusted to 3.0 pH and 6% \(w/v\) NaCl was added. Before the extraction, the GMeS was preconditioned by dipping it, subsequently, once in CH\({}_{3}\)OH and three times in deionized water. Then, the GMeS was deposited in 10 mL of the sample and agitated for 30 min at 600 rounds per minute. After each extraction, GMeS was put in a syringe cartridge, where it was washed multiple times with water and squeezed to wash away the excess water. The elution was done with 2 \(\times\) 1 mL of acetonitrile containing 5% \(v/v\) NH\({}_{3}\). The eluent was evaporated until dried, under a N\({}_{2}\) stream and the precipitate was reconstituted in 100 \(\upmu\)L H\({}_{2}\)O: Acetonitrile mixture of 70:30 \(v/v\), put into an ultrasonicator for 1 min and was finally injected into the HPLC valve. The recoveries of the proposed method were found to be 93%-105% for lake water samples and their enrichment factor 96-99. [PERSON] et al. [73] used modified GO nanosheets with trithiocyanuric acid for the enrichment and extraction of Cu(II) and Pb(II) ions in sea water samples prior to FAAS. Before starting the SPE extraction, the pH of the solution containing both ions was modified to 6.0 with 0.1 mol/L nitric acid or NaOH. Afterwards, it was permeated through the mini-cartridge packed with a standard amount of GO-TTC. The mini-cartridge was rinsed with 2 mL distilled water. Then, the effluate containing the adsorbed metal ions from the mini-cartridge was performed with 3 mL of 3 mol/L HNO\({}_{3}\). The amount of each ion in the effluate was determined by FAAS. [PERSON] et al. [74] developed lightweight GO-based sponges with high durability and compressibility for dye adsorption, specifically for methylene blue in wastewater samples. These sponges adsorbed and retained methylene blue when put in a solution that contains it and then the remaining concentration of the compound was determined by UV-vis spectrometry at 664 nm. The maximum adsorption capacity was observed at 476 mg/g sponge and its recyclability was found to be great, by adsorbing the target compound almost at 86% after the tenth cycle. [PERSON] et al. [75] also chose methylene blue from wastewater samples as their target compound for the selective adsorption on GO-montmorillonite/sodium alginate aerogel beads (GO-MMT/SA). Once again, the determination was carried out by UV-vis spectrometry and the residual concentration was calculated. The maximum adsorption capacity of the beads was considerably lower than the sponges, which was found to be 150.66 mg/g beads.