Polyaniline/graphene quantum dot-modified screen-printed carbon electrode for the rapid determination of Cr(VI) using stopped-flow analysis coupled with voltammetric technique

• The modification of PANI/GQD on SPCE was very simple and automated.
• The determination of Cr(VI) using the modified SPCE has been entirely investigated.
• The PANI/GQD-modified SPCE can be used several times without a renewal process.
• The developed method provided high sensitivity with low sample consumption (0.5 mL).
• The highest sample-throughput was found to be greater than 90 samples per hour.

Polyaniline/graphene quantum dots (PANI/GQDs) were used to modify a screen-printed carbon electrode (SPCE) in a flow-based system. A method for rapidly determining the Cr(VI) concentrations by using stopped-flow analysis has been developed using an Auto-Pret system coupled with linear-sweep voltammetry using the PANI/GQD-modified SPCE. The GQDs, synthesized in a botton-up manner from citric acid, were mixed with aniline monomer in an optimized ratio. The mixture was injected into an electrochemical flow cell in which electro-polymerization of the aniline monomer occurred. Under conditions optimized for determining Cr(VI), wide linearity was obtained in the range of 0.1–10 mg L−1, with a detection limit of 0.097 mg L−1. For a sample volume of 0.5 mL, the modified SPCE can be used continuously with a sample-throughput of more than 90 samples per hour. In addition, this proposed method was successfully applied to mineral water samples with acceptable accuracy, and the quantitative agreement was accomplished in deteriorated Cr-plating solutions with a standard traditional method for Cr(VI) detection.

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