Simultaneous analysis of multiple adulterants in milk using microfluidic paper-based analytical devices.

Area of Science:

• Analytical Chemistry
• Biosensors
• Materials Science

Background:

• Milk quality and safety are critical concerns, necessitating robust detection methods for adulterants.
• Existing analytical techniques can be time-consuming, expensive, and require specialized laboratory equipment.
• Microfluidic paper-based analytical devices (μPADs) offer a promising platform for low-cost, portable chemical analysis.

Purpose of the Study:

• To develop and validate μPADs for the simultaneous colorimetric detection of urea, H₂O₂, and pH in milk.
• To assess the performance of μPADs in terms of sensitivity, specificity, reproducibility, and accuracy compared to reference methods.
• To demonstrate the feasibility of using μPADs for rapid screening of milk adulterants without sample pretreatment.

Main Methods:

• Fabrication of μPADs using a craft cutter printer with integrated microfluidic channels and detection zones.
• Optimization of reagent and sample volumes for colorimetric assays (0.5 μL chromogen, 10 μL sample).
• Digital image analysis of colorimetric responses for quantitative detection of urea, H₂O₂, and pH.

Main Results:

• Linear detection ranges established: 0-30.0 mmol L^-1 (urea), 0-10.0 mmol L^-1 (H₂O₂), and 6.0-9.0 (pH).
• Limits of detection achieved: 2.4 mmol L^-1 for urea and 0.1 mmol L^-1 for H₂O₂; pH resolution of 0.25 units.
• μPADs demonstrated excellent reproducibility (RSD ≤ 6.0%), accuracy (91-102%), no cross-reactivity, and comparable results to reference techniques.

Conclusions:

• The developed μPADs provide a sensitive, specific, and cost-effective platform for simultaneous milk adulterant detection.
• This approach enables rapid, on-site screening of milk quality without the need for complex sample preparation.
• μPADs coupled with colorimetric analysis represent a powerful tool for ensuring milk safety and quality control.