Compound

Conc. ppm

Rct Ω cm2

Cdl *10 4 F cm−2

θ

% IEEIS

1 M HCl

- - -

129.4

0.689

-----

-----

Catharanthus extract

50

271.20

9.890

0.523

52.3

100

283.0

1.292

0.543

54.3

150

286.1

1.064

0.548

54.8

200

342.7

0.990

0.622

62.2

250

342.9

0.969

0.623

62.3

300

350.1

0.938

0.630

63.0