Table 1.
Combination of factors to assess the robustness of method.
| Factors | Nominal | Variation | ||||||
|---|---|---|---|---|---|---|---|---|
| Extraction time | A, 2.0 h | a, 1.5 h | ||||||
| Sample size | B, 250 mg | b, 225 mg | ||||||
| Particle size | C, 35 mesh | c, 40 mesh | ||||||
| Extraction temperature | D, 30°C | d, 40°C | ||||||
| Stirring | E, 120 rpm | e, 150 rpm | ||||||
| Extraction volume | F, 20.0 mL | f, 20.5 mL | ||||||
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| Factors level | ||||||||
| Combination | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
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| ||||||||
| Experiments | ||||||||
| A or a | A | A | A | A | a | a | a | a |
| B or b | B | B | b | b | B | B | b | b |
| C or c | C | c | C | c | C | c | C | c |
| D or d | D | D | d | d | d | d | D | D |
| E or e | E | e | E | e | e | E | e | E |
| F or f | F | f | f | F | F | f | f | F |
| Results | s | t | u | v | w | x | y | z |
(s) Nominal conditions of method. Variables: (t) particle size, stirring, and extraction volume; (u) sample size, extraction temperature, and extraction volume; (v) sample size, particle size, extraction temperature, and stirring; (w) extraction time, extraction temperature, and stirring; (x) extraction time, particle size, extraction temperature, and extraction volume; (y) extraction time, sample size, stirring, and extraction volume; (z) extraction time, sample size, and particle size.