Preliminary assessment of nicotine and pyridine occurrence in Bok Choy ( Brassica rapa subsp. chinensis ) following application of a Tobacco waste-derived biopesticide

Tobacco waste-derived biopesticides (TW-DBs) offer a potential approach to combine agricultural-waste valorization with crop protection; however, information on tobacco-derived compounds remaining on edible crops after application is limited. This preliminary study evaluated nicotine- and pyridine-associated analytical signals in bok choy (Brassica rapa subsp. chinensis) following foliar application of a TW-DB prepared by ethanolic heat reflux extraction. The formulation was applied at 2.5, 5.0, and 7.5 mL per 2 L of water, with a commercial pesticide as a reference. Leaf and root extracts were analyzed by GC-MS. Apparent nicotine-associated concentrations ranged from 0.75 to 1.36 mg/kg and pyridine-associated concentrations from 1.06 to 11.17 mg/kg. Signals were generally numerically higher in leaves, particularly for pyridine, but no statistically supported treatment or tissue differences were established, and concentrations showed no monotonic relationship with formulation volume. Given the duplicate biological measurements, absence of an untreated control, unquantified formulation concentrations, single harvest-time sampling, and lack of full matrix-specific analytical validation, these findings should be interpreted as exploratory occurrence data rather than evidence of treatment-derived residues, dose-response behavior, regulatory compliance, or consumer safety. Further confirmatory studies with adequate controls, replication, validated methods, quantified application concentrations, and time-resolved sampling are required.