Distance-based detection of paracetamol in microfluidic paper-based analytical devices for forensic application

Whisky adulteration is a prevalent practice driven by the high cost of these beverages. Counterfeiters commonly dilute whisky with less expensive alcoholic beverages, water, food additives, drugs or pharmaceuticals. Paracetamol (PAR), an analgesic drug that mitigates hangovers and headaches, is commonly used to adulterate whisky. Currently, the primary method for quantifying PAR levels is high-performance liquid chromatography, but this technique is both time consuming and usually generates more residues. In this context, the utilization of miniaturized and portable analytical devices becomes imperative for conducting point-of-care/need analyses. These devices offer several advantages, including portability, user-friendliness, low cost, and minimal material wastage. This study proposes the selective distance-based PAR quantification on whisky samples using a paper-based microfluidic analytical device (μPAD). Colorimetric detection on paper-based platforms offers great benefits such as affordability, portability, and the ability to detect PAR without complicated instrumentation. The optimal detection conditions were achieved by introducing 5 μL of a mixture containing 7.5 mmol L^-1 of Fe(III) and K₃[Fe(CN)₆] into the detection zone, along with 12 μL of whisky samples into the sample zone. The method exhibited linear behavior within the concentration range from 15 to 120 mg L^-1, with a determination coefficient of 0.998. PAR was quantified in adulterated samples. The results obtained with the paper-based devices were compared with a referenced method, and no significant differences were observed at a confidence level of 95%. The μPAD allowed to determine ca. 1 drop of pharmaceutical medicine PAR of 200 mg mL^-1 in 1 L of solution, demonstrating excellent sensitivity. This method offers cost-effective and rapid analysis, reducing the consumption of samples, reagents, and wastes. Consequently, it could be considered a viable and portable alternative for analyzing beverages at criminal scenes, customs, and police operations, thereby enhancing the field of forensics.