Simple flow injection for determination of sulfite by amperometric detection using glassy carbon electrode modified with carbon nanotubes–PDDA–gold nanoparticles

• CNTs–PDDA–AuNPs modified GC electrode was developed as a new sulfite sensor.
• The developed sensor exhibits excellent electrocatalytic activity.
• Detection on the electrode using FIA provides high sensitivity and selectivity.
• Analysis of sulfite in fruit juice and wine samples.

A new approach is presented for sensitive and selective measurement of sulfite (SO32−) in beverages based on a simple flow injection system with amperometric detection. In this work, the sulfite sensor was a glassy carbon electrode modified with multiwall carbon nanotubes–poly(diallyldimethylammonium chloride)–gold nanoparticles composites (CNTs–PDDA–AuNPs/GC). Electrochemical oxidation of sulfite with this electrode was first studied in 0.1 M phosphate buffer (pH 7.0) using cyclic voltammetry. The results indicated that the CNTs–PDDA–AuNPs/GC electrode possesses electrocatalytic activity for the oxidation of sulfite with high sensitivity and selectivity. Sulfite was quantified using amperometric measurement with the new sensor at +0.4 V vs Ag/AgCl in conjunction with flow injection. The linear working range for the quantitation of sulfite was 2–200 mg L−1 (r2=0.998) with a detection limit of 0.03 mg L−1 (3σ of blank) and an estimated precision of 1.5%.The proposed method was successfully applied to the determination of sulfite in fruit juices and wines with a sample throughput of 23 samples per hour.

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