Application of Gold Nanoparticles with 1,6-Hexanedithiol Modified Screen-Printed Carbon Electrode as a Sensor ‎for Determination of Arsenic in Tea and Coffee Samples

Abstract

The development of electrochemical nano sensor for the detection of total arsenic in tea and coffee samples was described based on the formation of gold nanoparticles (Au NPs). Screen printed carbon electrodes were modified with gold nanoparticles and linked with 1,6-hexanedithiol self-assembled monolayers. The electrode position of Au nanoparticles was performed in 10 mL of the solution that totally cover the screen-printed carbon electrode while applying a constant potential of -0.4 V (vs Ag within SPCE) for 600 sec. Cyclic voltammetry was used to characterize the gold nanoparticles before and after modified with 1,6-hexanedithiol self-assembled monolayers on screen printed carbon electrode. Square wave anodic stripping voltammetry with multi point standard addition method was used for the detection of As (III) and As(V) on Au NPs-1,6-hexanedithiol modified screen printed carbon electrode under optimized conditions. As (III) and As(V) was deposited for 60 seconds by the reduction of arsenic in buffer solution. It was found that Au- NPs with 1,6-hexanedithiol modified screen printed carbon electrode had a highest anodic stripping peak current at 0.201V.  The limit of detection value for arsenic was found to be 1.7 ng ml^-1. The limits of detections determined are below the corresponding guideline value from the World Health Organization (WHO). The developed method was successfully applied to determine arsenic in tea and coffee samples. In addition, seventeen different tea samples come from different countries of east Asia (China, India and SriLanka) and Egypt and eleven samples of coffee, which is the best-selling in the Libyan markets were also collected. The maximum of arsenic (0.167±0.015 mg/kg) was detected. Considering, the present safety standards the tea and coffee various selected in this study were determined to be fitted safe for human consumption. The limit value of the arsenic content was exceeded by (1.7%) only in one sample of dried black tea from Egypt (Aluorsa). The modified nano electrode exhibited excellent reproducibility and high stability.