Table 1 The mean percentage of caffeine obtained by the three methods
Methods | Mass of coffee (g) | Mass of solution (g)a | Mass of caffeine (g) | Caffeine in coffee (% w/w) | Mean ± SD (% w/w) |
|---|---|---|---|---|---|
FT-IR-ATR | 2.05 2.00 2.00 | 10.00 10.05 10.00 | 0.0334 0.0293 0.0294 | 1.629 1.465 1.470 | 1.520 ± 0.093 |
NIR | 2.05 2.00 2.00 | 10.00 9.980 10.00 | 0.0343 0.0289 0.0281 | 1.680 1.440 1.410 | 1.500 ± 0.14 |
Fluorescence | 0.5 0.5 0.5 | 65 75 70 | 0.0005682 0.0005255 0.0005624 | 1.434 1.530 1.529 | 1.497 ± 0.05 |
UV-Vis (for comparison) | 0.33 0.33 0.33 | Extracting volume 100 mL | 0.00453 0.00465 0.00466 | 1.373 1.409 1.410 | 1.397 ± 0.02 |