Table 2.
Sensitivity and regression parameters.
| Parameter | Method B | Method C |
|---|---|---|
| λ max, nm | 460 | 470 |
| Colour stability, min | 60 | 15 |
| Linear range, μg mL−1 | 0.4–8.0 | 0.4–10 |
| Molar absorptivity (ε), L mol−1 cm−1 | 4.0 × 104 | 3.7 × 104 |
| Sandell sensitivity*, μg cm−2 | 0.0105 | 0.0136 |
| Limit of detection (LOD), μg mL−1 | 0.39 | 0.43 |
| Limit of quantification (LOQ), μg mL−1 | 1.19 | 1.32 |
| Regression equation, Y** | ||
| Intercept (a) | 0.8744 | 0.8082 |
| Slope (b) | −0.0914 | −0.0815 |
| Standard deviation of a (S a) | 2.2 × 10−2 | 6.6 × 10−2 |
| Standard deviation of b (S b) | 4.9 × 10−3 | 7.3 × 10−3 |
| Regression coefficient (r) | −0.9998 | −0.9990 |
*Limit of determination as the weight in μg per mL of solution, which corresponds to an absorbance of A = 0.001 measured in a cuvette of cross-sectional area 1 cm2 and l = 1 cm. **Y = a + bX, where Y is the absorbance, X is concentration in μg mL−1, a is intercept, and b is slope.