A simple and efficient electrochemical sensor for folic acid determination in human blood plasma based on gold nanoparticles–modified carbon paste electrode

• We examine a AuNPs/CPE for direct electrooxidation behavior and determination of FA.
• Characterization of the electrode showed an obvious increase in surface area and porosity after modification.
• The modified electrode showed good ability to distinguish the electrochemical response of FA.
• The results were attributed to the specific characteristics of AuNPs present in the AuNPs/CPE.
• This paper demonstrated a simple and rapid sensor for determination of FA in plasma.

Folic acid (FA) is a water soluble vitamin that exists in many natural species. The lack of FA causes some deficiencies in human body, so finding a simple and sensitive method for determining the FA is important. A new chemically modified electrode was fabricated for determination of FA in human blood plasma using gold nanoparticles (AuNPs) and carbon paste electrode (CPE). Gold nanoparticles–modified carbon paste electrode (AuNPs/CPE) was characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The experimental parameters such as pH, scan rate (ν) and amount of modifier were studied by cyclic voltammetry and the optimized values were chosen. The electrochemical parameters such as diffusion coefficient of FA (DFA), electrode surface area (A) and electron transfer coefficient (α) were calculated. Square wave voltammetry as an accurate technique was used for quantitative calculations. A good linear relation was observed between anodic peak current (ipa) and FA concentration (CFA) in the range of 6 × 10− 8 to 8 × 10− 5 mol L− 1, and the detection limit (LOD) achieved 2.7 × 10− 8 mol L− 1, that is comparable with recently studies. This paper demonstrated a novel, simple, selective and rapid sensor for determining the FA in the biological samples.