Table 1. Four-step column chemistry used in this study to purify chromium.
| Eluent | Volume (ml) | Procedural step | Elements eluted |
|---|---|---|---|
| Step 1: 0.5 ml Biorad AG1-X8 200-400 mesh resin | |||
| 6M HCl | 2 | Condition | |
| 6M HCl | 0.5 | Sample Load | |
| 6M HCl | 3 | Cr collection | Cr + matrix |
| H2O | 5 | Wash | Fe + Ni |
| Step 2: 1 ml Biorad AG50W-X8 200-400 mesh resin | |||
| 0.5 M HCl | 3 | Condition | |
| 0.5 M HCl | 3 | *1Sample Load | |
| 0.5 M HNO3 | 20 | Cr collection | Cr + matrix |
| 6M HCl | 5 | Wash | Mg +; Ca + Al +; Mn + Ni |
| Step 3: 0.33 ml Biorad AG50W-X8 200-400 mesh resin | |||
| H2O | 1 | Condition | |
| 0.5 M HNO3 | 0.5 | *2Sample Load and Cr collection | Cr |
| 0.5 M HNO3 | 0.5 | Cr collection | Cr |
| 1M HF | 2.5 | Matrix elution | Ti + V + K + Na + Fe + Al |
| 1M HCl | 6 | Matrix elution | K+ Na |
| 6M HCl | 3 | Cr collection + Wash | Cr |
| Step 4: 0.75 ml Eichrom TODGA resin | |||
| 8M HCl | 2 | Condition | |
| 8M HCl | 0.5 | Sample Load | Cr |
| 8M HCl | 2 | Cr collection | Cr |
| H2O | 4 | Wash | V + Fe + Ti |
*1
Note: Sample pretreatment: dissolving sample in 0.25 ml 6 M HCl (in 7 ml beaker) with heating at >120 °C for more than 2 h, then added 2.75 ml H2O before loading. This is to transform Cr as Cr0
*2
Sample pretreatment: dissolving sample in 0.125 ml 2 M HNO3 (in 3 ml beaker) with heating at 100 ° C for 2 h, then added 0.01 ml H2O2 and 0.365 ml H2O, and put the mixture at room temperature for more than 24 h. This is to maximize the oxidation of Cr as Cr3+.