# Applications of Graphene-Based Nanomaterials in Environmental Analysis
## 3 Analytical Applications in Environmental Samples
### Applications of \(G\) and \(G\)  
[PERSON] et al. [59] used G as a sorbent in SPE for the preconcentration and determination of trace-level amounts of Co and Ni in tap water, river water and sea water. A 3 mL SPE column was packed with 60 mg of G and frits were placed above and below the solid to prevent any loss of the adsorbent. Then, 10 mL of methanol and 10 mL of deionized water were added to the column for equilibrium, cleaning and neutralization before usage. The pH of the sorbent was modified to the value of 5. Afterwards, 100 mL of an aqueous sample loaded with 2 mL of ammonium pyrrolidine dithiocarbamate was passed through the column. The column was then rinsed with 5 mL deionized water and the adsorbed analytes were extracted with 2 mL of 1 mol/L HNO\({}_{3}\) in acetone. Finally, the plate was collected and then measured with the help of a flame atomic absorption spectrometry (FAAS) instrument. Also, experiments of possible reusage of the sorbent were conducted, concluding that a single SPE cartridge packed with G could be reused for over 50 times. The recoveries of Co and Ni in tap water were 96.5-97.5% and 96.2-97.2% respectively, in sea water 96.8-98.0% and 96.5-97.0% and in river waters 96.5-100.5% and 96.6-99.8%. [PERSON] et al. [60] worked with a graphene oxide-silica composite coating in hollow-fiber solid phase microextraction (HF-SPME), which was online coupled with inductively coupled plasma mass spectrometry (ICP-MS) to determinate trace amounts of Mn\({}^{2+}\), Co\({}^{2+}\), Ni\({}^{2+}\), Cu\({}^{2+}\), Cd\({}^{2+}\) and Pb\({}^{2+}\) in environmental water samples. In particular, three water samples of well water, pond water and lake water were examined, which were collected and filtered with a 0.45 \(\upmu\)m membrane filter of and then their pH was adjusted to 1 with the addition of concentrated nitric acid for storage. Afterwards, for the extraction the pH was adjusted to the value of 5 with 0.1 mol/L nitric acid and NH\({}_{3}\cdot\)H\({}_{2}\)O. The LODs of the six metal ions Mn\({}^{2+}\), Co\({}^{2+}\), Ni\({}^{2+}\), Cu\({}^{2+}\), Cd\({}^{2+}\) and Pb\({}^{2+}\) were 7.5, 0.39, 20, 23, 6.7 and 28 ng/L respectively, while their recoveries were in the range of 85-107%, 88-93%, 90-92%, 91-112%, 100-107% and 87-119% respectively. [PERSON] et al. [61] utilized graphene as their sorbent in the extraction and determination of five sulfonylurea herbicides in environmental waters by Ultra-high Performance Liquid Chromatography- Mass Spectrometry (UHPLC-MS). Once again, 3 mL SPE cartridges were packed with G and they were rinsed with 10 mL of acetonitrile (ACN) and 10 mL of distilled water. 100 mL of the sample's solution were permeated through the cartridge and then, the cartridge was washed with 10 mL of ultra-pure water and the analytes were extracted with 6 mL of ACN, which contained 1% \(\
u\)/\(\
u\) CH\({}_{3}\)COOH. The solution eluted was evaporated under the stream of N\({}_{2}\) until dried and reconstituted in 1 mL ACN:Water (1:1 \(\
u\)/\(\
u\)). A 0.22 \(\upmu\)m nylon membrane filter was used for filtration prior to UHPLC injection. The method followed outstanding analytical performance, with the LODs ranging between 0.28-0.53 ng/L for the five herbicides, while the recoveries rates were 84.16-109.31%. [PERSON] et al. [62] synthesized GO and used it for the column SPE of Fe(III) and Mn(II) ions in water samples, used 3-(1-methyl-1H-pyrrol-2-yl)-1H-pyrazol-5-carboxylic acid (MPPC) as a chelating reagent and the determination was done by FAAS. At optimum conditions, Mn and Fe showed 145 and 162 ng/L respectively, while their recoveries were both 102% in tap water samples, 101% and 103% in mineral water samples respectively and 102-104% and 103% in river water samples. [PERSON] et al.