Figure 9.

CV catalytic oxidation peak currents (I_pa) of 0.010 M (A) matrine and (B) sophoridine at 0.05 V s⁻¹ for c-MWCNTs/PDEA films (a) in NaCl solution with pH 9.0 at 25 °C in the absence of Na₂SO₄ and methanol, (b) in NaCl solution with pH 9.0 at 25 °C containing 20% methanol but no Na₂SO₄, (c) in NaCl solution with pH 9.0 at 25 °C containing 0.35 M Na₂SO₄ but no methanol, (d) in NaCl solution with pH 9.0 at 40 °C in the absence of Na₂SO₄ and methanol, and (e) in NaCl solution with pH 4.0 at 25 °C containing no Na₂SO₄ and methanol.