Reactivity of DOPAL with NAL increases with pH. 100 µM DOPAL incubated with 10 mM NAL for 2 h in 50 mM Na2PO4 at pH 5, 6, 7, 7.4, 8, and 9 displays increased loss of DOPAL with increasing pH. Percent initial calculated as individual sample concentration relative to T = 0 concentration (n = 4). (A) Reaction time course demonstrating pH dependence for DOPAL reactivity with NAL. (B) The pseudo-first order rate constant (k') for the reaction of DOPAL with 10 mM NAL increases with pH.