| Sample No. | KC8H5O4 theoretical COD/(mg・L−1) | Cl− content/(mg・L−1) | Dilution fold | Found COD/(mg・L−1) | Relative error/% |
| 1 | 100 | 100 | 1 | 100.0 | 0 |
| 2 | 100 | 500 | 1 | 108.0 | 8.0 |
| 3 | 100 | 1000 | 1 | 113.7 | 13.7 |
| 4 | 100 | 2000 | 1 | 175.9 | 75.9 |
| 5 | 100 | 4000 | 1 | 324.3 | 224.3 |
| 6 | 100 | 8000 | 1 | 627.3 | 527.3 |
| 7 | 100 | 15,000 | 1 | 981.6 | 881.6 |
| 8 | 100 | 20,000 | 1 | 981.6 | 881.6 |