| Optimization Variables | Validation Parameters | |||||
| Variables | Studied range | Selected | Parameters | (Mercury) | (Copper) | |
| Acid concentration/M | (0.02 - 1.0) × 10−2 | 0.1 × 10−2 | Measurement wavelength (nm) | 435 | ||
| Reagent molar fold excess (M:L) | 1:1 - 1:40 | 15 | Linear range (μg∙mL−1) | 0.02 - 15 | 0.02 - 12 | |
| Temperature | Ambient | Ambient | Linearity equation | Y = −0.065x + 1.140 | Y = 0.203x + 0.113 | |
| Time/min | 1 - 20 | 10 | Standard deviation of the slope | 0.004 | 0.003 | |
| Stability | 1 min-72 hrs. | Correlation coefficient (r2) | 0.999 | 0.999 | ||
| Wavelength (nm) | 350 - 600 | 435 | Relative standard deviation (%) | 3.13 | 3.92 | |
| Extraction variables | Limit of detection, LOD (μg∙mL−1) | 0.031 | 0.024 | |||
| Extraction period/min | 1 - 30 | 10 | Limit of quantification, LOQ (μg∙mL−1) | 0.116 | 0.075 | |
| Aqueous phase volume/mL | 5 - 30 | 15 | Molar absorptivity, ε (L∙mol−1∙cm−1) | 1.41 × 104 | 3.16 × 105 | |
| pH | 1 - 10 | 5 | Sandall’s sensitivity (ng∙cm−2) | 4.169 | 3.165 | |
| pH of Cu replacement | 3 - 12 | 10 | Precision (%) of λmax (n = 10) | 0.105 | ||