Integrated four-leaf clover-like mip/pad for maleic hydrazide colorimetric determination

Sensitive and rapid detection of pesticide residues in foods are crucial for ensuring human safety. This study presents a laser-manufactured colorimetric Paper Analytical Device (PAD) integrating Molecularly Imprinted Polymer (MIP) for the detection of maleic hydrazide (MH), an anthropogenic plant growth regulator commonly found in vegetables. The PAD features a four-leaf clover-like design (4L-MIP/PAD) that facilitates a complete MH analysis process. Fabricated using a CO2 laser plotter, the PAD incorporates a CO2 laser-activated fiberglass layer functionalized with UV-synthesized MIP. The central region houses the MIP, while each foldable leaf performs a specific analysis step. The MH analysis involves depositing a 40 μL sample extract on the MIP. Unbound components are removed using capillarity by folding the ‘absorption-leaf,’ followed by washing with water and folding the ‘washing-leaf.’ Finally, an alkaline solution elutes the analyte, triggering a colorimetric reaction on the ‘colorimetric-leaf’ pre-loaded with Folin-Ciocalteu (FC) reagent. The 4L-MIP/PAD graphical sketch is reported in Figure. The analysis is completed within 30 minutes, and results are captured via smartphone camera. The 4L- MIP/PAD achieves MH quantification in the range of 5–60 mg/kg (RSD ≤ 17%, n=3) with a detection limit (LOD) of 1.4 mg/kg, meeting regulatory limits for vegetables like potatoes (50 mg/kg), carrots (30 mg/kg), and garlic/onions (15 mg/kg). Despite the non-selectivity of FC reagent, the 4L-MIP/PAD demonstrates high selectivity for MH over other pesticides and food matrix components. Recovery rates for garlic, onion, and carrot samples ranged from 82.0% to 123% (RSD ≤ 21%, n=3). This innovative laser-fabricated cloverleaf PAD offers an efficient and reliable approach for MH detection in food matrices.