Concentration dependence of the pseudo-first-order rate constant for the reaction of sulfide with DTNB. Representative stopped-flow kinetic trace for the reaction
of (A) 500 μM DTNB with 5 μM HS– or (B) 100 μM sulfide with 1 μM DTNB in 100 mM phosphate buffer at pH 7.40, 25 °C and I = 1 M. Experimental kinetic traces were recorded
at 412 nm ((A) blue dots, (B) red rhombs), where the solid black lines represent the corresponding single exponential fits. The pseudo-first-order rate constants
exhibit linear dependences on the (C) DTNB and (D) sulfide concentrations at an excess of DTNB and sulfide, respectively. Linear fits are represented by solid lines with the
obtained equations of (C) y = 0.881x – 0.0008 and (D) y = 0.893x – 0.0088.