| Element(ppm max) | Grade FNP-1 | Grade FNP-2 | Grade FNP-3 |
| Ta | 30 | 50 | 100 |
| O | 1500 | 2000 | 3000 |
| N | 200 | 400 | 600 |
| C | 200 | 300 | 500 |
| H | 100 | 200 | 300 |
| Si | 30 | 50 | 50 |
| Fe | 40 | 60 | 60 |
| W | 20 | 30 | 30 |
| Mo | 20 | 30 | 30 |
| Ti | 20 | 30 | 30 |
| Mn | 20 | 30 | 30 |
| Cu | 20 | 30 | 30 |
| Cr | 20 | 30 | 30 |
| Ni | 20 | 30 | 30 |
| Ca | 20 | 30 | 30 |
| Sn | 20 | 30 | 30 |
| Al | 20 | 30 | 30 |
| Mg | 20 | 30 | 30 |
| P | 20 | 30 | 30 |
| S | 20 | 30 | 30 |
