Flow injection analysis of cholesterol using FFT admittance voltammetric biosensor based on MWCNT–ZnO nanoparticles

•Very sensitive cholesterol sensor has been made by application CFFASV method.•Detection limit was improved to the lower amounts.•Response time is reduced to less than 8 s.•Detection limit of 0.050 ± 0.002 nM was achievable.

A new electrochemical method was designed for determination of cholesterol by combination of continuous admittance square wave voltammetry method and a highly sensitive biosensor. The new biosensor was constructed using immobilization of cholesterol oxidase (ChOx) on multiwalled carbon nanotubes (MWCNT) and ZnO nanoparticles (ZnO). The biosensor was used in a flow injection analysis system. The special square wave voltammetric method was established based on application of fast Fourier transform (FFT) and continuously calculating the biosensor admittance in a time window. The response of the injected cholesterol samples was calculated by background subtraction and integration of the biosensor signal in the recorded voltammograms in form of coulomb. The method is very sensitive and the response time is less than 8 s. The technique was applied as an electrochemical detector in a flow injection analysis system. Detection limit of the cholesterol was 0.05 nM in a linear range from 0.2 to 60.0 nM (R2 = 0.994).

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