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Percent recovery of fluoride.
| Pretreatment | Method | Percent recovery | ||||
|---|---|---|---|---|---|---|
| Ashed* | Direct and Diffusion | 18–24% |  |
 |
||
| Acid dissolution** | Direct | 75% |  |
|||
| Diluted in deionized water (1:10 w/v) | Direct | 67% |  |
 |
||
| No pretreatment | Direct | 84%–93% |  |
|||
| No pretreatment | Diffusion | 96%–100% | ||||
Mean for all ashing times
Samples were pretreated with perchloric acid/citrate/EDTA and NaOH
Statistically significantly different (p< 0.05)
