Fluorescence quenching spectrum of HSA in the presence of levamlodipine. Concentration of HSA was 2.0 × 10−5 M whereas the corresponding concentrations of levamlodipine were 0, 4, 12, 20, 24, 32, 40, 50, 60, 70, 80, and 90 × 10−6 M, respectively, as the arrow indicates. T = 298 K; λex = 290 nm; and λem = 340 nm.