Parameters SPAR ENO NOR LEVO λmax (nm) 417 436 419 436 Linearity range μgmL-1 0.5-7 1-10 1-10 1-5 Molar absorptivity 5.51 ×106 3.33 × 106 4.18  × 106 5.18 × 106 Slope 0.148 0.114 0.142 0.149 Intercept -0.0385 -0.0392 -0.0418 -0.0153 Correlation coefficient 0.9985 0.9986 0.9989 0.9994 LLOD ngmL-1 0.036 0.0041 0.0344 0.0063 LLOQ μgmL-1 0.11 0.0124 0.1043 0.019

Table 1: Optimum conditions and analytical parameters.