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A new electrode based on glassy carbon modified with an alginate film cross-linked with glutaraldehyde containing immobilized carbon black particles was successfully developed and applied for the determination of paraquat (PQ), a herbicide widely used for broadleaf weed control. Different polysaccharides (alginate, cellulose, pectin, starch, and chitosan) were investigated for the immobilization process, and alginate presented the highest chemical modifier potential for PQ determination. Additionally, the influence of chemical cross-linking agents (glutaraldehyde and epichlorohydrin) on the morphology, electrochemical response, and film stability was investigated. All experimental conditions were optimized, including the supporting electrolyte conditions (composition, pH, and concentration) and square wave voltammetry technical parameters. Under the optimized experimental conditions, the PQ analytical curve was linear from 0.4 to 2.0 mg L -1 and the limits of detection and quantification were 0.06 and 0.19 mg L -1 , respectively. The proposed electrode is easy to obtain, stable, selective, sensitive, and low cost and was successfully applied for PQ determination in environmental and beverage samples. Graphical abstract.