Fig. 4From: Sensitive and selective determination of vitamin B2 in non-alcoholic beverage and milk samples at poly (glutamic acid)/zinc oxide nanoparticles modified carbon paste electrodeNyquist plot of 5.0 mM [Fe(CN)6] 3−/4− in 0.1 M KCl at a BCPE, b ZnO NPs–CPE, c Poly(glutamic acid)/CPE and d Poly(glutamic acid)/ZnO–CPE at frequency range of 0.01 Hz – 100 kHz, applied potential of 0.15 V and amplitude of 0.005 VBack to article page