Parameters AVS λmax (nm) 566 Beer's law range (µg/mL) 2.0 - 20.0 Molar absorptivity (L/mol cm) 3.36×104 Stability (min) 1200 Stoichiometric relationship, AVS:MBTH 1:1 1:2 Logarithmic formation constants 5.9 8.6 Optimum photometric range (µg/mL) 4.2 - 15.7 Detection limit (µg/mL) 0.064 Sandell's sensitivity (µg/cm2 per 0.001 absorbance unit) 0.070 Regression equationa A = 0.029C-0.022 Correlation coefficient, R2 0.9998 a A = mC + b, where C is the concentration in μg/mL and A is the absorbance

Table 4: Analytical characteristics of the fixed time (800 sec) method.