Sustainable and efficient electrochemical determination of octopamine in Apis mellifera for stress monitoring.

This paper presents the design and validation of an electrochemical sensor for the detection of octopamine (OA) in vitro-reared larvae of honey bees (Apis mellifera) using glassy carbon electrodes modified with multi-walled carbon nanotubes and Kolliphor (p188). Octopamine, a key neurohormone involved in the stress response in insects, is studied as an indicator of the physiological and health status of bees under various stress factors. To validate the electrochemical method, a chromatographic approach based on ultra-high-performance liquid chromatography with fast-scanning fluorescence detection was developed, as well as a retro-microextraction system optimized using design of experiment and response surface methodology. The electrochemical method achieved limits of detection and quantification of 10.8 ng mL-1 and 32.4 ng mL-1, respectively. The validation study yielded a linear range of 0.054-108.00 μg mL-1, recoveries between 88 % and 101 %, and coefficients of variation from 6.9 % to 8.4 %. The ellipse analysis allows concluding that there are neither constant nor proportional systematic errors in the electrochemical determination. The proposed methodology allowed the successful quantitation of octopamine in vitro-reared honey bee larvae, both exposed and not exposed to heat stress. Its simplicity, portability, and environmental sustainability make it particularly suitable for decentralized applications and field analyses. Finally, it was effectively applied to quantify octopamine in vitro-reared honey bee larvae.