Quenching of 1O2 phosphorescence by TBBPA in MeCN/D2O mixtures. Plots of observed first order rate constants for 1O2 quenching as a function of TBBPA concentration. Line 1, alkaline solution (pD 13) containing 0.5 M NaOD in MeCN:D2O, 50%:50%, (Vol.:Vol.) mixture; kq = (1.44 ± 0.06) × 109 M-1 s-1. Line 2, neutral solution (pD 7.2) containing SB-12 (50 mM) and phosphate buffer pD 7.2 (10 mM) in MeCN: D2O, 20%:80% (Vol.:Vol.) mixture; kq = (3.9 ± 0.1) × 108 M-1 s-1.