| Sample | Equation TOC vs. S2 | R2 | Effect of matrix |
| Gs55 | y = 3.7962x − 0.1108 | 0.9944 | 0.029 |
| Gs83 | y = 3.3682x − 0.4114 | 0.8883 | 0.122 |
| Mish | y = 2.0663x − 0.2708 | 0.1675 | 0.131 |