| Substance | Linear regression equations | R2 |
| Acetic acid | y = 0.0024x – 0.0118 | 0.9967 |
| Propionic acid | y = 0.0154x – 0.0593 | 0.9977 |
| Isobutyric acid | y = 0.0339x – 0.0757 | 0.9974 |
| Butyric acid | y = 0.0330x – 0.0848 | 0.9983 |
| Isovaleric acid | y = 0.0429x – 0.1167 | 0.9991 |
| Valeric acid | y = 0.0430x – 0.1225 | 0.9997 |
| Caproic acid | y = 0.0233x – 0.0874 | 0.9951 |