Zahra Solati

Here, we have reported an effective and simple electrochemical techniquetodetermine folic acid (FA) in acolloidal suspension solution containing FeIII ion, methylene blue (MB) surfacecoated ZnO nanoparticles (MB@ZnONPs) and sodium dodecyl sulfate (SDS) (FeIII/MB@ZnONPs/SDS). MB, and ZnONPs were used as redox indicator and signal amplification element respectively. Low-concentration of MB (2.5 ?M) strongly is maintained at ZnONPs surface. SDS was used to improve the dispersion stability of the suspension. ZnONPs were synthesized through biological pathway using cordia myxa leaves extract. To investigate physicochemical propertiesofZnONPs and MB@ZnONPs,fourier-transform infraredspectra, nitrogen desorption/adsorption isotherms, field emission scanning elec tron microscopy and energy dispersive X-ray spectroscopy were used. Cyclic voltammetry and differential pulse voltammetry showed the positive effect of FeIII ion, on the redox behavior of the suspension solution, probably due to inhibiting effect of this cation on the agglomeration of MB@ZnONPs/SDSsuspension. Addition of FA to suspension solution,caused asharp decrease in the peak current. Therefore, the colloidal suspension solution employed as an analytical probe for FA determination. The response of the probe showed alinear dependence on the logarithm of FA concentration in the range of 1.42 nm to 3.30 ?M( I/?A=-0.26 Log [FA] 0.03, R2=0.99). The calculated limit of detection was 0.98 nM.