A fabrication-free headspace tape-based colorimetric method for rapid high-throughput nitrite screening in processed meats

Abstract

This study introduces a fabrication-free headspace tape-based colorimetric method for rapid and high-throughput screening of nitrite in processed meat products, employing a commercial adhesive tape (CAT) as the optical readout substrate. Nitrite is converted to volatile iodine via an acid-mediated nitrite–iodide redox reaction in a 96-well plate, thereby facilitating physical separation between the reaction medium and the optical detection surface. The iodine vapor produced is captured on the adhesive layer, resulting in a visible color change that is quantified through digital image analysis using a flatbed scanner. The adhesive surface enables uniform iodine adsorption and stable color development across the sensing area, thereby enabling reproducible image-based readout and high-throughput analysis in a 96-microwell plate. Commercial adhesive tapes were evaluated, and CAT1 (Scotch® Magic™ Tape 810) was identified as a suitable substrate for iodine vapor capture due to its color response and reproducibility. The optimized conditions were evaluated and gave a linear response over the nitrite concentration range of 0.5–2.5 mM (R² > 0.99), with an LOD of 0.17 mM, and inter-day precision was acceptable (10% RSD, n = 12). Excellent well-to-well reproducibility was attained across all 96 microwells, with a relative standard deviation (RSD) of less than 2%, thereby indicating minimal positional effects and a consistent signal distribution. Furthermore, temporal stability was observed, maintaining consistency over analysis durations of up to 90 min, with only minor variations in signal strength. The method showed acceptable selectivity, with minimal interference from common matrix components, although reductive species might interfere by consuming iodine. The method requires no reagent immobilization, surface modification, or organic solvents, resulting in a high Analytical GREEness (AGREE) score of 0.79. The sample preparation also demonstrated favorable greenness according to the AGREEprep metric (0.81), reflecting simple aqueous extraction and minimal handling. The colorimetric response remained stable over time, supporting reliable analysis. Its applicability was further confirmed by recovery studies on processed meat samples, which yielded recoveries of 80–110%, demonstrating its suitability as a rapid and practical screening method for nitrite in food safety monitoring.