Table 1.
Elemental concentrations of metals and metalloids (ppm by mass) present in graphite, HU-GO, and HU-RGOs and their expanded uncertainties (coverage factor k = 2) as determined by NAA
| Element | Elemental concentration (ppm) | ||||
| Graphite | HU-GO | HU-TRGO | HU-NaBH4 | HU-N2H4 | |
| Ag | <0.12 | <0.06 | <0.11 | 2.22 ± 0.17 | 1.90 ± 0.17 |
| Al | 5.2 ± 1.6 | <60 | <110 | 310 ± 70 | 420 ± 80 |
| As | <0.03 | 0.056 ± 0.012 | 1.08 ± 0.12 | <1 | <17 |
| Ba | <3 | <7 | <9 | 19 ± 5 | 570 ± 40 |
| Ce | <0.3 | <0.1 | <0.3 | 5.9 ± 0.4 | 1.20 ± 0.17 |
| Co | <0.01 | 0.157 ± 0.013 | 6.2 ± 0.4 | 2.17 ± 0.16 | 1.42 ± 0.10 |
| Cr | <0.4 | 1.82 ± 0.15 | 50 ± 4 | 5.2 ± 0.4 | 9.2 ± 0.7 |
| Cs | <0.03 | 0.028 ± 0.008 | <0.15 | <0.03 | <0.05 |
| Cu | <1.2 | 130 ± 40 | <200 | <200 | <400 |
| Fe | <18 | 82 ± 6 | 270 ± 20 | 123 ± 12 | 144 ± 16 |
| Hf | <0.03 | <0.01 | 0.055 ± 0.014 | 0.33 ± 0.05 | 0.26 ± 0.02 |
| In | 0.016 ± 0.002 | <0.1 | <0.8 | 0.63 ± 0.12 | 1.97 ± 0.14 |
| K | <30 | 820 ± 60 | 2,410 ± 180 | <1,400 | <10,000 |
| La | 0.031 ± 0.004 | <0.004 | <0.3 | <0.15 | <2 |
| Mn | 0.14 ± 0.02 | 2,290 ± 160 | 5,700 ± 400 | 3,800 ± 300 | 3,000 ± 200 |
| Na | 1.0 ± 0.3 | 96 ± 7 | 138 ± 10 | 7,600 ± 500 | 420 ± 70 |
| Sb | <0.009 | 0.012 ± 0.003 | <0.3 | 0.068 ± 0.016 | 0.37 ± 0.04 |
| Sc | <0.002 | 0.0017 ± 0.0004 | 0.011 ± 0.001 | 0.021 ± 0.002 | 0.024 ± 0.002 |
| Ta | <0.013 | <0.006 | 0.26 ± 0.02 | 0.066 ± 0.006 | 0.038 ± 0.004 |
| Th | <0.04 | <0.013 | <0.03 | 0.059 ± 0.013 | <0.04 |
| V | 0.059 ± 0.014 | <1.8 | <5 | <5 | 9 ± 2 |
| Zn | <0.8 | <150 | 3.0 ± 0.8 | 114 ± 8 | 169 ± 12 |
Values below the detection limit of the NAA procedure are also shown. These values and to a lesser extent, the uncertainties vary as a function of the matrix composition, including nonmetal and nonmetalloid elements.