Table 1.
Summary of digestion conditions used for the method optimization.
| Factor | Levels |
|---|---|
| Acid mixture | HNO3 (100%), HNO3:H2SO4 (1:1), HNO3:H2SO4 (1:2), H2SO4 (100%) |
| Digestion hold time (min) | 15, 30, 45 |
| Digestion set temperature (°C) | 190, 210 |
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